Digital Exciter

GEH-6375

EX2000PWM Digital Exciter

User’s Manual

EX2000PWM Digital Exciter

User’s Manual

GEH-6375

Issue Date: June 1997

These instructions do not purport to cover all details or variations in equipment, nor to provide for everypossible contingency to be met during installation, operation, and maintenance. If further information is desiredor if particular problems arise that are not covered sufficiently for the purchaser’s purpose, the matter should bereferred to GE Motors & Industrial Systems.

This document contains proprietary information of General Electric Company, USA and is furnished to itscustomers solely to assist that customer in the installation, testing, operation, and/or maintenance of theequipment described. This document shall not be reproduced in whole or in part nor shall its contents bedisclosed to any third party without the written approval of GE Motors & Industrial Systems.

1997 by General Electric Company, USAAll rights reserved.

Printed in the United States of America

EX2000 PWM Digital Exciter GEH-6375

a

SAFETY SYMBOL LEGEND

WARNING

Indicates a procedure, practice, condition, or statement that, if not strictly observed, could result inpersonal injury or death.

CAUTION

Indicates a procedure, practice, condition, or statement that, if not strictly observed, could result indamage to or destruction of equipment.

NOTE

Indicates an essential or important procedure, practice, condition, or statement.

GEH-6375 EX2000 PWM Digital Exciter

b

WARNING

This equipment contains a potential hazard of electric shock or burn. Only personnel who areadequately trained and thoroughly familiar with the equipment and the instructions should install,operate, or maintain this equipment.

Isolation of test equipment from the equipment under test presents potential electrical hazards. Ifthe test equipment cannot be grounded to the equipment under test, the test equipment’s case mustbe shielded to prevent contact by personnel.

To minimize hazard of electrical shock or burn, approved grounding practices and proceduresmust be strictly followed.

WARNING

To prevent personal injury or equipment damage caused by equipment malfunction, onlyadequately trained personnel should modify any programmable machine.


i

TABLE OF CONTENTS

Section/Subject Page

CHAPTER 1. OVERVIEW

1-1. Description Scope ....................................... 11-2. Introduction ................................................. 11-3. EX2000 System Overview.......................... 31-3.1. Hardware Design...................................... 31-3.1.1. Control Core (Regulator Module) ......... 41-3.1.2. Power Converter Module ...................... 51-3.1.3. Optional Hardware Modules ................. 51-3.2. Software Design ....................................... 61-3.2.1. Software ................................................ 61-3.2.2. Ac and Dc Regulators............................ 61-3.2.3. Scaling................................................... 71-3.2.4. Faults ..................................................... 71-3.2.5. Simulator ............................................... 71-3.3. Human-Machine Interface........................ 8

CHAPTER 2 HARDWARE SYSTEMDESCRIPTION

2-1. Introduction ................................................. 92-2. Packaging .................................................... 92-2.1. Environmental .......................................... 92-2.2. Enclosure.................................................. 92-3. Ratings......................................................... 92-3.1. Input Ratings ............................................ 102-3.1.1. PMG Input............................................. 102-3.1.2. Auxiliary Bus Input............................... 102-3.1.3. Bus Feed From the Generator ............... 102-3.1.4. Dc Input Power...................................... 102-3.2. Output Current Rating.............................. 102-3.3. Voltage Control Range............................. 112-3.4. Power Profile Rating ................................ 112-4. Power Converter Hardware......................... 122-4.1. Ac and Dc Input Drives............................ 122-4.2. Dc Link and Dynamic Discharge ............. 132-4.3. IGBT and IAXS Devices.......................... 132-4.4. Output Contactor MDA............................ 132-4.5. Output Shunt SHA.................................... 132-5. Control Electronics Module ........................ 142-5.1. TCCB (DS200TCCB) .............................. 142-5.2. PSCD (DS200PSCD) ............................... 142-5.3. GDDD (IS200GDDD).............................. 15


2-5.4. PTCT (DS200PTCT).................................. 152-5.5. NTB/3TB (531X305NTB) ......................... 152-5.6. LTB (531X307LTB) .................................. 152-5.7. RTBA (DS200RTBA)................................ 152-5.8. ACNA (DS200ACNA)............................... 152-6. Inputs and Outputs......................................... 152-6.1. Generator Inputs ......................................... 152-6.1.1. Potential Transformer Inputs................... 152-6.1.2. Current Transformer Inputs..................... 162-6.2. 4-20 MA Inputs .......................................... 162-6.3. Generator Line Breaker Status ................... 162-6.4. Generator Lock-Out Trip............................ 162-6.5. Additional I/O............................................. 16

CHAPTER 3 SOFTWARE SYSTEMOVERVIEW

3-1. Introduction ................................................... 253-2. Configuration Tools ...................................... 253-3. Programmer Module...................................... 253-3.1. Using the Programmer................................ 253-3.2. Software Design ......................................... 263-4. Standard Function.......................................... 263-4.1. Automatic Voltage Regulator (AVR) Ramp.............................................. 263-4.2. Automatic Voltage Regulator Setpoint ...... 263-4.3. Automatic Voltage Regulator..................... 263-4.4. Field Regulator (FVR) Ramp ..................... 263-4.5. Field Regulator ........................................... 273-4.6. Under Excitation Limiter (UEL) ................ 273-4.7. Over Excitation Limiter (OEL) ................. 273-4.8. Firing Block................................................ 27

CHAPTER 4 SOFTWARE CONFIGURATIONAND SCALING

4-1. Introduction ................................................... 374-2. Configuration and Scaling Example.............. 374-2.1. Example Generator, Exciter and Regulator 374-2.1.1. Generator Data......................................... 374-2.1.2. Exciter Data ............................................. 384-2.1.3. Regulator Data......................................... 38


ii


4-3. Generator Configuration ..............................384-4. Feedback Scaling..........................................394-4.1. Generator Feedback...................................394-4.1.1 Potential Transformer Failure Detector (PFTD) Operation.................................. 404-4.1.2. PTFD Scaling ........................................ 404-4.1.3. PTFD Detection Level........................... 404-4.1.4. P.T.U.V.................................................. 404-4.2. Bridge Voltage Feedback ......................... 404-4.3. Bridge Current Feedback.......................... 414-4.4. Feedback Offsets ...................................... 414-4.5. Instantaneous Overcurrent Trip................ 414-5. Regulator Scaling ........................................ 424-5.1. Automatic Voltage Regulating System .... 424-5.1.1. AVR Operation...................................... 424-5.1.2. REF1 Operation..................................... 424-5.1.3. REF1 Scaling and Configuration .......... 424-5.1.4. Autosetpoint Block................................ 434-5.1.5. Autosetpoint Block Scaling and Configuration......................................... 434-5.1.6. Automatic Voltage Regulator (AVR) Block......................................... 444-5.1.7. AVR Scaling and Configuration ........... 444-5.1.8. AVR Proportional Gain......................... 454-5.1.9. Integral Gain.......................................... 454-5.2. Under Excitation Limiter (UEL) .............. 454-5.2.1. UEL Operation ...................................... 454-5.2.2. UEL Scaling andConfiguration ............. 464-5.2.3. UEL Curve............................................. 464-5.3. Reactive Current Compensator (RCC)..... 484-5.4. VAR/Power Factor Control...................... 494-5.4.1. VAR//PF Control Operation and Configuration........................................ 494-5.5. Field Regulator (FVR) ............................. 504-5.5.1. REF2 Operation..................................... 504-5.5.2. REF2 Scaling and Configuration .......... 504-5.5.3. FVR Operation ...................................... 504-5.5.4. FVR Scaling .......................................... 514-5.5.5. Transfer Tracking Meter and Balance... 514-5.6. Field Current Regulator (FCR) ................ 514-5.6.1. Alternate FCR........................................ 524-5.6.2. Alternate Field Current Regulator Scaling .................................................. 524-5.6.3. Primary FCR.......................................... 534-5.6.4. Primary Current Regulator Scaling and Configuration ................................. 534-6. Optional Functions Scaling and Configuration.............................................. 54


4-6.1. Transducer Outputs ....................................544-6.2. Ground Detector and Diode Fault Monitor ......................................................554-6.2.1. Ground Detector and Diode Fault Scaling and Configuration ...................... 554-6.3. Field Thermal Model.................................. 564-6.3.1. Thermal Model Operation ....................... 564-6.3.2. Thermal Model Scaling ........................... 56

CHAPTER 5 STARTUP CHECKS

5-1. Introduction ................................................... 575-2. EX2000 Prestart Checks................................ 575-2.1. Energization and Simulator Control Checks........................................................ 575-3. Pre-Start Power Checks................................. 595-4. Initial Roll Off-Line Checks.......................... 615-5. On-Line Checks............................................. 625-6. Operator Interface.......................................... 635-6.1. Units with UC2000 or IOS......................... 635-6.2. Units with Discrete Switches and Meters... 63

CHAPTER 6 SIMULATOR SCALING ANDOPERATION

6-1. EX2000 PWM Simulator .............................. 656-1.1. Simulator Scaling ....................................... 656-1.2. Operation .................................................... 67


1

CHAPTER 1

OVERVIEW

1-1. DEFINITION AND SCOPE

This manual describes the EX2000 Pulse WidthModulated (PWM) Digital Regulator for brushlessgenerator excitation systems. This is amicroprocessor controlled power converter thatproduces controlled dc output for rotating exciter,brushless generator applications.

This manual is intended to assist applications andmaintenance personnel in understanding theequipment hardware and software. It also providesinitial startup information.

The manual is organized as follows:

Chapter 1 – OverviewBriefly defines the EX2000 PWM regulatorwith an overview of the hardware and softwaredesign. Includes references to other manualsand documents, one-lines and connectiondiagrams.

Chapter 2 – Hardware System DescriptionContains specific information on systemhardware design and purpose, ratings, I/Odefinition.

Chapter 3 – Software System OverviewContains specific information on softwaretools, structure, functions, and one-linerepresentations.

Chapter 4 – Software Configuration andScaling

Gives examples of the scaling for specificparameters in a generic brushless regulatorgenerator application.

Chapter 5 – Startup ChecksContains pre-start, startup, and on-lineadjustments required during the commissioningof the PWM regulator for a brushless excitationsystem.

Chapter 6 – Simulator Scaling andOperation

Gives example simulator scaling and operationinstructions for a typical brushless regulatorgenerator application.

1-2. INTRODUCTION

The EX2000 PWM regulator controls the acterminal voltage and/or the reactive volt amperes ofthe generator by controlling the field of the rotatingbrushless exciter. Figure 1-1 shows a typical one-line system of a PMG fed brushless generatorapplication. Power for the regulator is normallysupplied from a Permanent Magnet Generator(PMG) driven directly by the main generator field.This can be a single phase or three phase PMG. Analternative method is to obtain excitation regulatorpower from a Power Potential Transformer (PPT)supplied from an auxiliary bus. This can also be asingle or three phase supply. The PPT is required toensure an ungrounded input to the regulator. Asecond power source is also possible from a dcbattery source.


2

The control system contains both a generatorterminal voltage regulator and an exciter fieldcurrent regulator. These are known as the automaticor ac regulator and the manual or dc regulatorrespectively.

When operating under control of the dc regulator, aconstant exciter field current is maintained,regardless of the operating conditions on thegenerator terminals. When operating under controlof the ac regulator, a constant generator terminalvoltage is maintained under varying load conditions.If the generator is connected to a large systemthrough a low impedance tie, the generator cannotchange the system voltage appreciably. The acregulator, with very small variations in terminalvoltage, then controls the reactive volt amperes(VARs).

If the generator is isolated from a system, the acregulator controls the terminal voltage and theVARs are determined by the load. Most systemsoperate in a manner that is between these twoextremes. That is, both VARs and volts arecontrolled by the ac regulator. Normal operation iswith the ac regulator in control, with an automatictransfer to the dc regulator in the event of loss ofpotential transformer feedback as detected throughPotential Transformer Failure (PTF) or PTUndervoltage Detection (PTFD).

In the EX2000 PWM regulator, PT FailureDetection requires two sets of PT inputs. There isautomatic tracking between the ac and dc regulatorsto ensure a bumpless transfer in either direction. Abalance signal is available for display on theoperator station or turbine control interface. Atransfer between regulators can be initiated by theoperator or, if supplied, by the PT failure detectionalgorithm. In addition to the reference input to theac regulator summing junction, a number of bothstandard and optional inputs are possible. Seesection 1-3.2.2.

Besides the regulating functions, the excitationsystem contains protective limiter functions, startupand shutdown functions, and operator interfaces thatare implemented in both hardware and/or software.

The software is accessed via an RS-232Ccommunication link by using the SuperTool 2000(ST2000) program or GE Controls Systems Toolboxfor Windows NT or Windows 95. These toolkits aremicroprocessor based software used to configureand maintain GE’s EX2000 regulators and exciters.It consists of a collection of programs (tools)running under a command shell.

The EX2000 PWM regulator includes a Local AreaNetwork (LAN) and RS-232C interfaces for externalcommunication, which includes using the ST2000toolkit that can be purchased separately.


3

Figure 1-1. PMG Brushless Exciter Overview

1-3. EX2000 SYSTEM OVERVIEW

1-3.1. Hardware Design

The EX2000 PWM hardware consists of a controlcore and a power converter section, described inChapter 2. The controller includes printed wiringboards containing programmable microprocessorswith companion circuitry, including electrically-erasable programmable read-only memory(EEPROM) where the regulator’s system blockwarepattern is stored.

The power converter consists of input disconnectsand filters, a dc link with charge control, IGBTdevices, output contactor and shunt, and controlcircuitry.

There are also optional hardware devices availableon the EX2000 PWM such as 4-20 ma transducers,Power Potential Transformers, and Field GroundDetector Power supplies.


4

1-3.1.1. CONTROL CORE (REGULATORMODULE). Referring to Figure 2-3 the controlcore is mounted in two board racks on the outside ofthe core panel and is accessible while the regulatoris operating. Also, behind the hinged outer door,several Input/Output (I/O) boards are mounted. (SeeFigure 2-4) The control core consists of all thesecircuit boards interconnected by ribbon cables andharnesses, which keep wiring to a minimum.Detailed hardware information including fuse andtest point information, replacement instructions andboard layouts are provided in the referenceddocuments for each of the following circuit boards.

Power Supply and Contactor Driver (PSCD)Instruction Book GEI - 100241

The PSCD board creates internal power supplies andredistributes the necessary power supply voltagesfor the other control core circuit boards. An isolated70 V dc supply is also produced and used for LTBboard inputs. The PSCD board also produces thecontactor coil voltage for the MDA output andcharge control contactor.

Gate Driver and Dynamic Discharge (GDDD)Instruction Book GEI - 100240

The GDDD board controls the gating of the IGBTsfor bridge output and Dynamic Discharge control. Italso isolates and scales DC output, DC link voltage,shunt feedback and heat sink temperature feedbacks.

LAN Terminal Board (LTB)Instruction Book GEI - 100022

The LTB board provides an interface betweencontrol devices and external devices such ascontactors, relays, indicators, lights, pushbuttonsand interlocks.

Microprocessor Application Board (TCCB)Instruction Book GEI - 100163

The TCCB contains software transduceringalgorithms that mathematically manipulate the

inputs from the isolation and scaling printed wiringboards. These inputs are analog feedback signalsfrom the current and voltage transformers, whichmonitor generator output and line voltage, and fromthe bridge ac input and dc output voltages and shuntfeedbacks.

I/O Terminal Board (NTB/3TB)Instruction Book GEI - 100020

The NTB/3TB board includes an RS-232Ccommunication port for connecting to a personalcomputer (PC). The optional field ground detectorinputs are connected to the NTB board.

Drive Control and LAN Control Board (LDCC)Instruction Book GEI - 100216

Reprogramming the LDCC boardInstruction Book GEI - 100217

The LDCC controls LAN communication andpermits operator access and control via theProgrammer keypad. It also contains the drivecontrol microprocessor which monitors start/stopsequencing, alarms, trips and outer loop regulatorsand motor control microprocessors which monitorsthe field voltage and current regulators, gating andovercurrent protection.

Relay Terminal Board (RTBA)Instruction Book GEI - 100167

The RTBA board provides seven output relays withform C contacts available for customer use whichcan be driven from a remote input or directly fromthe relays on the LTB board.

ARCNET Link (ACNA)

The ACNA board provides the connection point forthe ARCNET Lan communications


5

1-3.1.2. POWER CONVERTER MODULE

Figure 1-2. EX2000 Brushless Unit

The power conversion section consists of an inputsection, a dc link, and the converter output section.The input section is a three phase diode bridge withinput filters. The range of the ac input is from 90volts rms up to 275 V rms. Frequency inputs rangeas high as a nominal 360 hz. It can be a single phaseor three phase input from a PMG, auxiliary bus orgenerator terminal fed. An input PPT is notrequired for the PMG input. A PPT is required foran auxiliary bus or generator terminal feed. Anoptional voltage doubling feature is available forunits requiring higher forcing capability.

An optional backup source from nominal 125 or 250V dc batteries is filtered, diode isolated andcombined with the three phase diode bridge output.These sources charge the power capacitors through acharge control resistor, RCH, which forms the dclink portion of the power converter module. The dclink is the unregulated source voltage for the controlcore power supplies and the output power throughthe IGBTs. A coarse control of the voltage level ofthe dc link is provided by the dynamic dischargecircuit. This circuit will dissipate excess powerfrom the dc link (possible due to a regenerationeffect from the field of the rotating exciter) through

the dynamic discharge resistor, RDD. This circuit isnormally powered from the PSCD board but may bepowered through the dynamic discharge powersource resistor RDS if control power is lost.

The converter output section takes the dc link sourcevoltage and pulse width modulates it through theIGBT devices. The output voltage is determined bythe following formula:

Voutput = Vinput * (time on/(time on + time off))

where Vinput is the dc link voltage, time-on is theconduction time of the IGBT devices and time-off isthe non-conduction time of the IGBTs. Thechopping frequency of the IGBTs is approximately1000 hz. See Figure 5-1.

This output is fed to the rotating exciter field as aregulated voltage or current. A single pole contactfrom the MDA contactor isolates the regulator fromthe field. An output shunt monitors the fieldcurrent.

1-3.1.3. OPTIONAL HARDWARE MODULES.There are a limited number of structured optionsavailable with the EX2000 PWM regulator. Up to


6

four 4-20 ma output transducers are available forcustomer use. They are driven from D/A converterslocated on the NTB board, and are non-adjustabledevices. Scaling is provided in the EX2000 PWMsoftware.

A 50/60 hz, 25 kVA Power Potential Transformer(PPT) is available for units that are connected to anauxiliary bus or generator output terminals. ThisPPT may or may not be supplied inside the regulatorenclosure. Power to the primary should be fused perthe application notes found in the control elementarysupplied with the equipment. This transformer issized to supply rated excitation requirementscontinuously and still be capable of operation atceiling excitation for a short time.

An optional Field Ground Detector Power supplymay be supplied for some systems. This powersupply provides 24 V control power to the Fieldmonitor unit mounted in the generator exciterhousing. A 120 V ac feed is required to power thissupply.

1-3.2. Software Design

The regulator application software consists ofmodules (building blocks) combined to create therequired system functionality. Block definitions andconfiguration parameters are stored in read-onlymemory (ROM), while variables are stored inrandom-access memory (RAM). Microprocessorsexecute the code.

Diagnostic software is transparent to the user. AProgrammer module with a digital display andkeypad allows an operator to request parametervalues and self-checks.

1-3.2.1. SOFTWARE. The exciter applicationsoftware emulates traditional analog controls. Thesoftware uses an open architecture system, whichuses a library of existing software blocks. Theblocks individually perform specific functions, suchas logical AND gates, proportional integral (P.I.)regulators, function generators, and signal leveldetectors.

These blocks are tied together in a pattern toimplement complex control functions. For example,a control function such as the under-excitation limit(UEL) is included as an ac regulator input by settingsoftware jumpers in EEPROM. The relevantblockware is enabled by pointing the block inputs toRAM locations where the inputs reside (the UELrequires megawatts, kilovolts and megavars). TheUEL output is then pointed to an input of the acregulator summing junction. The software blocksare sequentially implemented by the blockinterpreter in an order and execution rate defined inthe ST2000 tools.

The blockware can be interrogated while running byusing the ST2000 Tools. The dynamically changingI/O of each block can be observed in operation.This technique is similar to tracing an analog signalby using a voltmeter.

1-3.2.2. AC AND DC REGULATORS. The ac orAutomatic regulator and, dc or Manual regulator aresoftware functions again emulating traditionalanalog controls. The ac regulator reference is froma static counter and is compared to the generatorterminal voltage feedback to create an error signal.In addition to the reference signal input to the acregulator summing junction, the following inputscan be used to modify the regulator action. (Thepower system stabilizer (PSS) is an optionalfunction.)

Reactive Current Compensation (RCC). Thegenerator voltage is allowed to vary in order toimprove reactive volt amp (VA) sharing betweengenerators connected in parallel. Generator voltagedecreases as overexcited reactive current increases,and increases as underexcited reactive currentdecreases. Alternatively it can be used to provideline drop compensation.

Under-excitation Limit (UEL). Under-excitedVARs must be limited to prevent heating of thegenerator iron core and to ensure dynamic stabilityof the turbine generator. This is done by an under-excitation limiter that takes over when a specifiedlimit curve is reached and prevents operation belowthis limit.


7

CAUTION

V/Hz. The ratio of generator voltage to frequency(V/Hz) must be limited. This prevents overfluxingthe generator and/or line-connected transformerscaused by overvoltage operation or under-frequencyoperation, or a combination of the two.

Power System Stabilizer (PSS). The introductionof a high gain, high initial response exciters cancause dynamic stability problems in power systems.The advantage of these exciters is to provideimproved transient stability, but this is achieved atthe cost of reduced dynamic stability and sustainedlow frequency oscillations.

The PSS is fed with a synthesized speed signalbased on the integral of accelerating power. Thisindicates the rotor deviation from synchronousspeed. This signal is conditioned and fed into thesumming junction of the continuously-acting acregulator so that under deviations in machine speedor load, excitation is regulated as a compositefunction of voltage and unit speed. The stabilizertherefore produces a damping torque on thegenerator rotor and consequently increases dynamicstability. The PSS is an optional function.

Over-excitation Limiter (OEL). It is necessary tolimit generator excitation current off-line to preventoverfluxing the generator and connectedtransformers. On-line, it must be limited to preventfield thermal damage. The limiting action isperformed by the excitation current regulator. Thecurrent regulator takes control of bridge gating if theregulator (automatic or manual) calls for a fieldcurrent that produces main generator field excitationcurrent in excess of a predetermined pick-up level.

The dc or manual regulator is configured as a fieldcurrent regulator using the shunt feed back as areference compared to the manual regulator staticadjust reference. It will maintain a constant exciterfield current based on the setpoint adjuster. The online and off line field current regulators are lowvalue gate selected with the manual regulator outputto select the appropriate firing level for the IGBTbridge.

1-3.2.3. SCALING. It is necessary to scale thesoftware in each exciter for application with aparticular generator. The regulators use normalizedvalues of counts to represent one per unit (1 pu).

Typically 1 pu equals either 5000 or 20000 counts.This means that the feedback value for a particularvariable, such as field voltage (VDCLINK = 1 pu)or bridge current (AFFL = 1 pu), must benormalized by using a multiplier to equal theprerequisite value of counts when it is at 1 pu. SeeChapter 4 for more details.

1-3.2.4. FAULTS. The EX2000 has asophisticated self-diagnostic capability. If aproblem occurs, a fault code flashes in theProgrammer display showing a fault name andnumber. The fault number also appears on thedisplay on the LDCC in coded form. GEI - 100242includes information on fault codes, interpretation,and troubleshooting.

1-3.2.5. SIMULATOR. Located within the coresoftware is a sophisticated system simulationprogram that models the exciter and generatorbehavior. The simulator is activated via a softwarejumper in EEPROM.

The simulator physically operates thefield contactors when a start signal isissued to the exciter. If dc link voltageis present, current may flow in theexciter field.

Signals representing the field and the generatorfeedbacks are simulated in the TCCB and fed to thetransducering algorithms, in place of the realfeedbacks. Once the exciter is scaled for aparticular generator, the simulator uses that scaling.For example, after a successful startup sequence isperformed in simulator mode, the operator interfacewill displays the exciter voltage and current andgenerator voltage applicable to that particular unit.This tool is useful for training, startup, andcalibration checkout.

Scaling and operation of the simulator is discussedin Chapter 6.


8

1-3.3. Human - Machine Interface

Each EX2000 PWM will have a human - machineinterface (HMI) device of some form. The standardoffering will be via a data link with the turbinecontroller over the Status S page and regulatorinformation will be obtained through the turbinecontrollers HMI. Other interfaces offered may

include, but are not limited to, discrete switches andmeters, direct DCS control through a UC2000, orsome other device. Refer to the control elementarysupplied with the equipment for the devicesprovided and to that device’s specific instructionbook for further information.


9

CHAPTER 2

HARDWARE SYSTEM DESCRIPTION

2-1. INTRODUCTION

This chapter describes the EX2000 PWM regulatorhardware structure, and overall operation. Whenreading these descriptions, refer to Figure 1-2, thespecific unit elementary, and the excitation layoutdiagrams provided with the equipment.

2-2. PACKAGING

GEI-100228 provides information on Receiving,Storing, and Warranty Instructions for DIRECTO-MATIC 2000 Equipment. This document should beconsulted upon receipt of the EX2000 PWMregulator.

Each regulator will endure the followingenvironmental conditions without damage ordegradation of performance.

2-2.1. Environmental

Temperature requirements for the EX2000 PWMshould be maintained within the shipping andstorage limits in GEI - 100228 during transport andhandling. Once installed, the operational limits ofan ambient temperature of 0 to +45 °C, outside ofthe convection cooled cabinet, should bemaintained. It is expected that the hottest boardentry temperature will be approximately 60 °Callowing the use of 70 °C parts.

5 to 95% relative humidity with no externaltemperature or humidity excursions that wouldproduce condensation should also be maintained.

The EX2000 PWM control equipment is alsodesigned to withstand 10 PPB of the followingcontaminants:

Reactive SulfurReactive ChlorineHydrogen SulfideSulfur DioxideChlorine DioxideSulfuric AcidHydrochloric AcidHydrogen ChlorideAmmonia

2-2.2. Enclosure

The standard enclosure offering is a NEMA 1 orIP20 equivalent, 90 inches high by 24 inches wideand 20 inches deep. An optional 36 inch wideenclosure is also available. In some instances, justthe regulator panel without enclosure will beprovided. This panel measures approximately 63inches high by 17 inches wide by 18.5 inches deep.Other enclosure types are available.

Estimated weight is 1200 pounds with NEMA 1, 24inch enclosure, 900 pounds without enclosure.

Estimated watts losses are a maximum 200 watts forall applications.

2-3. RATINGS

In the interest of producing a robust design, allpower components, including the IGBT package,were chosen with an operating limit of at least 50 Awhere practical. This overdesign of componentsshould provide the long life and reliability desired ina generator excitation regulator.

Each EX2000 PWM regulator has a specific outputlimit rating based on the application of the regulatorand limited by the shunt chosen for the application.The following ratings information is the maximumoutput of the standard regulator, using a 25 A shunt.For shunt ratings other than 25 A, the output current


10

limitations will be reduced proportionately. Nameplate information should be used for accurateratings.

2-3.1. Input Ratings

The ac input is the primary input power to thebrushless regulator. The range of input ac is from90 V rms. up to 275 V rms. The ac input may besingle or three phase. The input ac may be from apermanent magnet generator (PMG), customersupplied auxiliary bus, or bus fed from thegenerator.

The ac source input to the EX2000 PWM regulatorshould have an impedance of 6 % nominal based onan estimated 20 A, 10 kVA source.

2-3.1.1. PMG INPUT. The voltage and frequencyfor PMG based input will start from 0 and increaseto rated as a function of generator speed. Ratedinput from the PMG system can be as high as 250 Vac rms / 360 Hz. Nominal voltages can be 100 V acrms up to 250 V ac rms. With overspeed conditions,the maximum is 275 V ac rms / 440 Hz. Since thePMG is ungrounded and is only used to sourcepower to the brushless regulator, no inputtransformer is required.

PMG systems on gas turbines will see extendedperiods of time at < 50 % speed operation onstartup. This is due to the purge cycle needed by thegas turbine. Since the PMG may be the only inputpower to the regulator, the control will initialize at≤ 60 V ac rms (i.e. ~50% speed).

2-3.1.2. AUXILIARY BUS INPUT. Auxiliarybus based systems require an input transformer toisolate the input to the brushless regulator from thecustomer power system. This is to insure that thepower source to the brushless regulator isungrounded. The transformer can be external to theenclosure that houses the brushless regulator butwill generally be located in the panel. Thesecondary voltage can range from 90 V ac rms up toa max. 275 V ac rms. Nominal secondary voltagescan be 100 V ac rms. up to 250 V ac rms. Ratedfrequency for the auxiliary bus based systems can be50 Hz or 60 +/- 10%.

2-3.1.3. BUS FEED FROM THEGENERATOR. Bus Fed based systems willrequire an input transformer to isolate the input tothe brushless regulator from the power system. Thisis also to insure that the power source to thebrushless regulator is ungrounded. The transformerwill be external to the enclosure that houses thebrushless regulator. The secondary voltage canrange from 90 V ac rms up to a max. 275 V ac rms.Nominal secondary voltages can be 100 V ac rms upto 250 V ac rms. Rated frequency for the bus feedbased systems can be 50 Hz or 60 +/- 10 %.

If a bus fed system is applied on a black-start gasturbine, this input may start at 20 % of rated speed,therefore, the voltage and frequency will start at20 % of rated.

2-3.1.4. DC INPUT POWER. The dc sourceinput power is generally provided from a batterybus. This source is a back-up to the primary acinput power source. It can be used as the primaryinput power for starting black-start turbinegenerators.

The nominal battery bus voltages are based on a110/125/ 220 / 250 V dc. Therefore, the operatingrange for the dc input is from 80 V dc up to a max.of 290 V dc.

2-3.2. Output Current Rating

The bridge is capable of delivering the followingabsolute maximum output:

• 25 A dc continuously over the specifiedtemperature range

• 40 A dc for 20 s once every 30 minutes aftercontinuous operation at 25 A dc over thespecified temperature range.

The PWM bridge is monitored for excessivetemperature by a heatsink sensor. Both alarm andtrip signals are available.


11

2-3.3. Voltage Control Range

The PWM bridge is capable of two quadrantoperation (positive and negative output voltage,positive current). This allows operation near zerovoltage. The PWM bridge has two active transistorsand will operate in zero vector mode. This willallow the output voltage to be chopped in PWMfashion from +V dc to 0 for positive voltagecommands and -V dc to 0 for negative voltagecommands. The chopping frequency isapproximately 1 khz.

The IGBT bridge does not provide a low impedancepath which would provide rectification when gatingis disabled. This prevents runaway conditionsknown to occur on brushless units having rotatingdiode failure. The four flyback diode structureprovides this inherently.

2-3.4. Power Profile Rating

The output power profile is a function of lineimpedance, line current rating, operating point (I dcand V dc), and capacitor current rating. Peakcurrent is limited by IGBT rating. In general highercurrent output is available at lower output voltages.Output current (I dc) can be higher than line currentrating. The regulator shall be capable of matchingthe following power profile.

The continuous operating area is bounded by theminimum of the capacitor limit, line limit, 25 A dc,or maximum output curve and the x (V dc) and y(I dc) axis.

The y axis shows input line amps (rms), capacitoramps (rms), or output amps (dc) for a given outputV dc and I dc. The curve labeled 25 shows rmscapacitor current on the y axis for a given V dc and25 I dc.


12

0 50 100 150 200 250 300 3500

5

10

15

20

25

30

35

25

25 Adc

Output voltage (Volts dc)

Line and capacitor currents as functions of dc voltage and current

line limit 12.5 Arms

cap limit 10 Arms

Line (A rms), capacitor (A rms), or output (A dc) current

IGBT limit25Adc

at 50 Vdc and 25 Adccapacitor current is10 Arms

at 200 Vdc and25 Adc

line currentis 15 Arms

maximumoutput

Figure 2-1. Typical Power Profile

The curve labeled 25 A dc shows rms line current onthe y axis for a given output V dc and 25 I dc.

The line limit curve corresponds to given V dc and Idc which would result in rated line current. The caplimit curve corresponds to given V dc and I dcwhich would result in rated capacitor current. Thefollowing graph illustrates the various limits.

Negative voltage operation is not shown.

2-4. POWER CONVERTER HARDWARE

For the following discussions, elementary drawing03A and the panel layout drawings (Figures 2-2 thru2-5) should be used references. The elementary

sheet is typical for all applications. On arequisition basis, the output shunt (SHA), chargeresistor (RCH), and dynamic discharge resistor(RDS) may change. Also, various combinations ofthe input source power may exist. A single phasePMG with battery backup is assumed.

2-4.1. Ac and Dc Input Devices

The ac input device DSWAC is a three phase, 600 Vac, 30A molded case industrial circuit breaker. Forsingle phase applications, the L1 and L3connections should be used. The dc input deviceDSWDC is a two phase, 250 V dc, 30 A moldedcase industrial circuit breaker. These input devicesare mounted at the top of the panel, easily accessiblefor operation as a disconnect during equipmentmaintenance or inspection.


13

The ac input source is filtered by snubber RCnetworks and rectified by a three phase diode bridge(DM1, 2 and 3). The dc output of this bridgecharges capacitors C1, C2, C3, and C4, forming thedc link. The dc supply is filtered through inductors(LPDC and LNDC) and battery capacitor C1F. It isthen fed directly to the dc link through isolationdiode DM4. MOV1 and MOV2 are provided forsurge protection. All of these components arelocated at the top of the panel, behind the ac and dcdisconnects.

2-4.2. Dc Link And Dynamic Discharge

A charge control resistor (RCH) mounted on theheat sink assembly is provided to limit inrushcurrent during power up and capacitor charging.The second pole of the MDA contactor controlsapplication or removal of the charge control resistor.The dc link provides the source power for internalboard power supplies via cable DCPL to the PSCDboard. The control power supply is designed tooperate over a range of 60 to 600 V dc on the dclink.

Auxiliary diodes DM5 allow stored energy in theexciter to be returned to the dc link when the outputcontactor MDA opens. Excessive voltage buildup inthe dc link during regeneration is controlled throughthe dynamic discharge circuit. This circuit monitorsthe level of the dc link and will dissipate energythrough the dynamic discharge resistor (RDD)mounted at the top of the panel to preventovervoltage of the power circuit and board racksupply. The C leg of the 3 phase IGBT pack iscontrolled by the dynamic discharge circuitry on theGDDD board. An alternate source of power for thedischarge circuit is provided through the RDSresistor, also to the GDDD board, in the event thatcontrol power is lost. Jumper settings on the GDDDboard set the control level of the dc link by thedynamic discharge circuit.

2-4.3. IGBT And IAXS Devices

The dc link also provides the unregulated powersource for the Insulated Gate, Bi-polar Transistor(IGBT) bridge used to provide the exciter fieldcurrent. The bridge consists of legs A and B of the

three phase, 50 A, 1200 V IGBT pack. Only leg Aupper and leg B lower IGBT’s are active. Leg Alower and leg B upper are permanently inactive.Controlled by the microprocessor based digitalregulator, the leg A and B IGBT’s are modulated topulse the dc link supply and feed the resultingoutput to the field of the rotating brushless exciter.The output voltage is determined by the followingformula:

Voutput = Vinput * (time on/(time on + time off))

where Vinput is the dc link voltage, time on is theconduction time of the IGBT devices and time off isthe non-conduction time of the IGBTs. Thechopping frequency of the IGBTs is approximately1000 hz.

The IAXS board provides the connection of the dclink capacitors to the IGBT bridge, dynamicdischarge control and gate control from the GDDDboard. The IAXS board is also the connection pointfor the dc output voltage and sensing feedbacks tothe control circuitry.

2-4.4. Output Contactor MDA

The output contactor MDA is described in GEK -83756. It is a double pole, single throw, 600 V dc,50 A contactor, isolating the positive leg of theEX2000 PWM bridge output. The second pole isused to remove the charge control resistor RCH.The power for the contactor coil is provided fromthe PSCD board. This voltage is only present whenthe control has been commanded to run. When theDC link voltage is not present, there is no poweravailable to drive this contactor.

2-4.5. Output Shunt SHA

The output current is monitored by the control viathe 100 mv feedback shunt SHA. The shunt ratingis application specific. A range from 1 A to 25 Amaximum is possible. The shunt rating must be lessthan twice the exciter amps full load.


14

2-5. CONTROL ELECTRONICS MODULE

The control electronics module contains powerfulprogrammable microprocessors with companioncircuitry, including EEPROM, to process theapplication software. It is a module assembly that islocated on the front door assembly of the powerconversion module. Elementary diagram sheet A04and Figure 2-7 shows the connections of the variousboards in the control module.

This control module assembly contains the mainprocessor board (LDCC), microprocessorapplication board (TCCB), power supply andcontactor driver board (PSCD), and the gate driverboard (GDDD). These boards are interconnectedthrough ribbon cables. The following is a brieffunctional description of the boards within theexciter. Each board has a unique GEI whichdocuments the hardware layouts, test points, fusesand other information for each individual board.These are referenced in Chapter 1.

The LAN and Drive Control Board (LDCC), whichis the main processor board, provides the IGBTgating circuit control and regulator functionsincluding:

• Automatic voltage regulator

• Field current regulator

• Field current limit regulator

• Volts/hertz limit regulator

• Reactive current compensation

• Under-excitation limit regulator

Optional functions include:

• VAR/power factor regulator

• Power system stabilizer

The LDCC board also contains both isolated andnon-isolated circuits for communication inputs tothe exciter’s controller. The LED display andkeypad programmer is on this board.

2-5.1. TCCB (DS200TCCB)

The microprocessor application board (TCCB) isessentially a transducer board. The isolated andscaled generator PT and CT signals are fed from thePTCT board to the TCCB board. The TCCB usesvoltage controlled oscillators (VCOs) to transformthe analog voltage signals into digital signals.Software transducers process the voltage and currentsignals and then calculate generator data. Thisinformation is passed to the LDCC controlprocessors for use by the regulators. The EX2000PWM simulation software also resides in the TCCB.

2-5.2. PSCD (IS200PSCD)

The Power Supply and Contactor Driver board(PSCD) is powered from the dc link via stab-onterminals DCPL1 (+) and DCPL2 (-). The controloperates from 80 - 400 V dc as nominal range inputs.Transient operation to 600 V dc is possible duringmaximum operation of the dynamic discharge. Thisboard produces control power for distribution to theother control module boards. The main supplyproduces +/- 24 V, +/-15 V, and +5 V for controlboards (LDCC and TCCB, etal.) A 17.7 V acsquarewave is distributed through high frequencytransformers to the gate driver and LTB inputs powersupplies. Auxiliary to the main supply are suppliesfor generating isolated 70 V dc (sufficient to power13 LUP inputs ) and an isolated SHVI/SHVM powerfor future applications.

The contactor control power supply from the PSCDboard is sized to deliver up to 0.75 A dc. Power istaken directly from the dc link and converted to 105V dc by a buck converter. The enable of the MDAcontactor is via an optically coupled signal which islogically in parallel with the coil of K1. Relay K1 isdriven from the LDCC board when the control iscommanded to run.

Relay K86 is used as the controls permissive to runand emergency stop. Dropping out K86 willimmediately stop the EX2000 PWM regulator. Coilvoltage is from the 70 V dc power supply on thePSCD board.


15

2-5.3. GDDD (IS200GDDD)

The Gate Driver and Dynamic Discharge board(GDDD) provides the interface isolation betweenthe IGBTs and the main processor firing circuits.Dynamic discharge circuit control is implementedon the GDDD board as well as the gating circuits forthe A leg and B leg active IGBTs.

The board also provides the instrumentation of theEX2000 PWM. Output dc voltage, dc link voltage,shunt current mv input, and the heat sink thermistorinput are processed on the GDDD board and sent tothe LDCC processors for use by the regulators.

2-5.4. PTCT (DS200PTCT)

The Potential Transformer Current Transformer(PTCT) board isolates and scales the voltage andcurrent signals from the PTs and CTs. It alsoprovides auxiliary inputs and outputs for either lowvoltage (± 10 V dc) or 4-20 ma current signals.Secondaries of the isolation transformers are passedto the TCCB board via the JKK ribbon connector.

2-5.5. NTB/3TB (531X305NTB)

The NTB/3TB serves as a general purpose terminalconnection board. Connections are made as aninterface between the control core and other devices.The EX2000 PWM RS-232C serial port is locatedon this board. When supplied, the field grounddetection inputs from the ground detector receiverare connected to the auxiliary VCO inputs on theNTB/3TB board.

2-5.6. LTB (531X307LTB)

The LAN Terminal Board (LTB) is an I/Otermination board that serves as an interfacebetween the control core and other devices. Ribboncable RPL allows software variables pointed to theseven low voltage, low current, form C LTB outputrelays to control higher voltage, higher current, formC RTBA board relays. Jumper settings on the

RTBA board determine if the LTB relays or externalconnections operate the RTBA relays. The eightLTB (or LUP) inputs are connected to the LDCCboard via 8PL for use by the regulator controls.

2-5.7. RTBA (DS200RTBA)

The Relay Terminal Board (RTBA) board containsseven form C, DPDT relays that can be softwaredriven via the LTB pilot relays or externally driven.The relay contact outputs are used for externalcustomer interface. Each relay contains an LED thatindicates when the relay is energized.

2-5.8. ACNA (DS200ACNA)

The ARCNET Board (ACNA) serves as theconnection for the ARCNET data link for theEX2000 PWM regulator. Termination is madeusing co-axial cable. Each ACNA can terminatetwo co-axial cables.

The Status S data link connection to the turbinecontroller is made on the ACNA board.

2-6. INPUTS AND OUTPUTS

The EX2000 PWM regulator has a limited amountof hard inputs and outputs that can be supported.For most applications, these will be conducted overthe Status S data link. As a minimum, the followingmust be supported in the basic brushless regulatorfor basic/OEM offerings.

2-6.1. Generator Inputs

2-6.1.1. POTENTIAL TRANSFORMERINPUTS. Up to three sets of three phase PT inputsare supported. These inputs are a nominal 120 Vsecondary with software adjustments available forother nominal secondary voltages. The inputs areless than a 10 VA burden on the PT inputs.

The first two PT sets are used to supply generatorline voltage feedback information to the automatic(ac) regulator for control of the generator output


16

voltage. The first PT set is used for generatorcontrol. The second set is used for PT failuredetection and can be configured for control shouldthe first set fail.

These inputs also supply speed / frequency feedbackinformation for the regulators, limiters, andprotection functions, including the optional PowerSystem Stabilizer (PSS).

The third set of three phase PT inputs provides lineside voltage and is used by the control for anoptional voltage matching feature. Theseconnections are made directly to the PTCT board.

Optional PT isolation switches for all three sets ofinputs may be supplied.

2-6.1.2. CURRENT TRANSFORMER INPUTS.One set of two phase CT inputs is supported. PhaseA and phase C currents are required by the EX2000PWM regulator. These CTs supply generator linecurrent feedback information for use by regulator,limiters, and metering functions in the brushlessregulator control, including the optional PowerSystem Stabilizer (PSS). The inputs require anominal 5 A secondary CT input. Softwareadjustments are available down to a nominal 3 Asecondary input. The CT burden is less than 1 VAper phase. These connections are made directly tothe PTCT board.

Optional CT isolation shorting switches for eachphase input may be supplied.

2-6.2. 4 - 20 MA Inputs

Optionally, the EX2000 PWM regulator can supporttwo 4 to 20 milli-amp inputs for signals used tomodify the overexcitation limiter / protection basedon the cooling of the generator. On air cooledgenerators this input will be proportional to thecooling air temperature for the generator. Onhydrogen cooled generators this input will be basedon hydrogen pressure of the generator.

2-6.3. Generator Line Breaker StatusOne form A contact input from the generator outputcircuit breaker is used by control, limiter, andprotection functions. This contact is connected toan LTB input. The contact may be powered usingthe 70 V dc supply from the PSCD board.

2-6.4. Generator Lock-Out Trip

One form A (closed when reset) contact input froma customer trip relay (86G typically) is supportedfor an external trip of the excitation control system.This contact must be powered from the 70 V dcpower supply on the PSCD board.

2-6.5. Additional I/O

In addition to the I/O listed above, the followingminimum inputs and outputs are supported.

Not all applications will require each of the contactI/O or 4-20 ma inputs or outputs listed. Refer to thejob specific elementary for those supplied.

Input Regulator On / Off (Closed = Regulator On)This is used to start and stop the brushless regulator.

Input Regulator Selector AC/DC (Closed = AC )This is used to select the controlling regulator, auto(AC) or manual (DC).

Input Regulator Raise (Close = Raise)This interfaces to the active regulator’s referenceadjuster, ac or dc, and raises the setpoint.

Input Regulator Lower (Close = Lower)This interfaces to the active regulator’s referenceadjuster, ac or dc, and lowers the setpoint.

Input PSS Enable/Off (Closed = Enable)This contact allows the PSS control to operate ifminimum load permissives are reached.

Input Status of Control Output ContactorThis contact is used to monitor the status of theMDA contactor.


17

Output Exciter Alarm (30EX)This output provides a global exciter trouble alarmfor customer annunciation

Output Protective Transfer to dc Regulator /Transfer Regulator alarm (60EX)This contact provides an indication of an automatictransfer to manual regulator

Output Regulator OnThis contact provides an indication that the EX2000PWM regulator is operating.

Output Exciter Trip Request (94EX)This contact output is a request from the EX2000PWM to immediately trip the generator. Usuallydirected to the 86G device.

Output Exciter Field Ground Alarm/Trip (64FA or64FT)This contact output can be either an alarm or tripcontact depending on customer preference.

The voltage inputs supported are:

Input from Exciter Field Ground Detector Alarm(+ 24 V)Input from Exciter Field Ground DetectorMalfunction (+24 V)Input from Exciter Field Ground Detector DiodeFault (+24 volts)

Up to four 4 to 20 milli-amp outputs are alsosupported.

These outputs are provided through the digital toanalog converters on the NTB/3TB board. They aresoftware configurable. Typical uses are regulatoroutput voltage, regulator output current, andregulator balance.


18

Note: Not Certified for Construction.

Figure 2-2. Mechanical Layout


19

Figure 2-3. Front View


20

Figure 2-4. Front View (Door Removed)


21

Figure 2-5. Bridge Components


22

Figure 2-6. Bridge Components (Isometric)


23

MAINPROCESSOR

BOARD

LDCC

MICROPROCESSORAPPLICATION

BOARD

TCCB

POWER SUPPLYAND

CONTACTOR DRIVERBOARD

PSCD

GATE DRIVER ANDDYNAMIC DISCHARGE

BOARD

GDDD

PTCTBOARD

ARCNET BOARD

ACNA

LTB RTBA NTB/3TB

POWER CONVERTERMODULE (IGBT)

WORKSTATION

CONTACTINPUTS

CONTACTOUTPUTS

CONTACTINPUTS/OUTPUTS

TO TURBINE CONTROLOPERATOR INTERFACE

METER DRIVEROUTPUTS QTY (4)

3 PHASEVOLTAGESENSING

INPUT

2 PHASECURRENTSENSING

INPUT

RS232PORT

DC OUTPUTTO

EXCITER FIELD

AC INPUT

DC INPUT

Figure 2-7. Typical Connection Diagram


24

Notes:


25

CHAPTER 3

SOFTWARE SYSTEM OVERVIEW

3-1. INTRODUCTION

The EX2000 PWM regulator uses microprocessorbased software that includes adjustable parameters.These parameters perform many functions oncecontrolled through adjustable hardware and softwarecombinations.

The parameters are modified to customize theregulator to the specific hardware and application.They also enable field and maintenance personnel tofine tune the regulator for optimal performance.

Either the DOS-based ST2000 Toolkit or Windows-based Toolbox and the LDCC board Programmerare used for making these software adjustments.These products are available as options from GEMotors & Industrial Systems for use by thecustomer.

The programmer is provided with each unit.

3-2. CONFIGURATION TOOLS

DOS based ST2000 and Windows-based GEControl System Toolbox are software toolkits usedto configure, maintain, and fine tune the EX2000PWM regulator. They consist of a collection ofprograms (tools) running under a command shell onan IBM PC-compatible computer.

The toolkit includes an extensive database ofEX2000 definitions, accessed and manipulatedusing menu driven selections. Additionally, theST2000 program can graphically display theexciter’s program logic on the computer screen. Byviewing the logic flow, the user can betterunderstand and manipulate the exciter’s adjustablevalues.

ST2000 is used at the factory to initially configureand test the systems. At the customer site, the toolsenable GE field engineers and other trained

personnel to troubleshoot, fine-tune, and maintainthe installed EX2000 PWM regulator. Optional toolbased modules provide real display of controlvariables and communications data.

Publication GEH-5860 provides instructionalinformation about DOS ST2000. Publication GEH-6333 provides information about the Windows-based Toolbox. These publications also include thePC requirements for running the tools.

3-3. PROGRAMMER MODULE

The EX2000 PWM regulator includes a Programmermodule with a 16 character digital display and analphanumeric keypad. It functions as an operatorinterface for software adjustments and diagnostictesting when the ST2000 Toolkit is not available.

NOTE

Permanent changes made using theProgrammer module must also be madein the configuration tools to keep themup to date with the exciter’s softwareconfiguration. Contact GE Motors &Industrial Systems for support in thisarea.

3-3.1. Using The Programmer

Publication GEI-100242 provides information onhow to operate the Programmer module.


26

3-3.2. Software Design

The exciter application program consists offunctional software modules (building blocks)combined to perform to system requirements. Blockdefinitions and configuration parameters are storedin read-only memory (ROM), while variables arestored in random-access memory (RAM).Microcontrollers execute the code.

The exciter application software emulates traditionalanalog controls. The software uses an openarchitecture system, which uses a library of existingsoftware blocks. The blocks individually performspecific functions, such as logical AND gates,proportional integral (PI) regulators, functiongenerators, and signal level detectors.

These blocks are tied together in a pattern toimplement complex control systems. For example, acontrol function such as the under-excitation limit(UEL) is included as an ac regulator input by settingsoftware jumpers in EEPROM. The relevantblockware is enabled by pointing the block inputs toRAM locations where the inputs reside (the UELrequires megawatts, kilovolts and megavars). TheUEL output is then pointed to an input of the acregulator summing junction.

The software blocks are sequentially implementedby the block interpreter in an order and executionrate defined in ST2000. The blockware can beinterrogated while running by using ST2000. Thedynamically changing I/O of each block can beobserved in operation. This technique is similar totracing an analog signal by using a voltmeter.

3-4. STANDARD FUNCTIONS

Table 3-1 is a description of the inputs and outputsfor the more significant blocks used in the EX2000.These inputs and outputs can be monitored throughST2000, if desired. Also, the significantadjustments of those functional blocks are describedas Adjustable Constants. These constantsrepresent limits, gains, and setpoints. They arefunctionally equivalent to potentiometers or otherdiscrete adjustment devices used in previousexcitation systems.

3-4.1. Automatic Voltage Regulator (AVR)Ramp

The AVR ramp block accepts an input from theoperator via the Status-S page for auto regulatorraise or lower. The reference then ramps at apredetermined rate, within an upper and lower limit(usually 0.9 to 1.1 pu terminal V). The output canbe preset to a value upon startup. Automatictracking of the AVR track value is performed whenoperating in manual regulator. Refer to Figure 3-2.

3-4.2. Automatic Voltage Regulator Setpoint

The AVR setpoint block sums the output from thereactive current compensation (RCC), AVR ramp,UEL output, and power system stabilizer (PSS)output. This sum is compared to the V/Hz referencein a minimum select block and then passed througha high limiter as the AVR output signal. Byselecting a negative or positive gain, line-drop ordroop compensation mode may be selected on theRCC. An auto/manual command via the operatorgenerates auto active or manual active statusindicators. A PT failure can also select manual.Refer to Figure 3-3.

3-4.3. Automatic Voltage Regulator

The AVR block combines the AVR setpoint withthe negative generator terminal volts to provide anerror signal. This is passed through to the automaticregulator proportional and integral gain sub-blocks,and then passes through the auto regulator limits tothe manual voltage regulator. The auto regulator ismodeled by the following transfer function:

AVR out = AVR error (Kp + KI)/S. See Figure 3-4.

3-4.4. Field Regulator (FVR) Ramp

The FVR ramp block accepts an input from theoperator via the Status S page for manual regulatorraise or lower. The reference then ramps at apredetermined rate within an upper and lower limit


27

(usually 0.7 pu VFNL to 1.2 pu VFFL). The outputcan be preset to a value upon startup. When in autoregulator mode, the FVR ramp tracks the value ofIFE, exciter field current. Refer to Figure 3-5.

3-4.5. Field Regulator

The exciter field regulator is configured as a currentregulator in the EX2000 PWM. The reference inputto the FVR is from either the manual regulator rampblock or the AVR. When fed from the AVR, thefield regulator is used as an inner loop. A bridgefiring enabled signal is also provided to keep theexciter turned off until bridge firing has beenenabled. Refer to Figure 3-6.

3-4.6. Under Excitation Limiter (UEL)

The UEL blocks accept watts and volts as inputs andcalculates a VAR reference. Using a table lookupwhich approximates the underexcited capability ofthe generator, the VAR reference is then comparedto the actual unit VARs to develop a VAR errorsignal. The error signal is then passed through aproportional and integral regulator sub-block to keepthe machine within its underexcited capability.Refer to Figure 3-7.

3-4.7. Over Excitation Limiter (OEL)

In the EX2000 PWM, the alternate current regulatoris initially enabled. If the signal level detect lookingat exciter field current or either of the inverse timeprotection blocks activate, the alternate field currentregulator is disabled and the primary currentregulator setpoints are active. The output of eitherthe alternate or primary field current regulator is fedto the firing block where a minimum select with thefield regulator firing command is performed. A cooldown function is also supplied to simulate coolingof the field after an overexcitation condition. Referto Figure 3-8.

3-4.8. Firing Block

The firing block accepts the field current referenceand the field voltage reference and then selects theleast of the two. This signal is passed on to thebridge only if the instantaneous overcurrent or thestop commands are not activated. If either of theseare active, the firing signal is a preset retard limit.Refer to Figure 3-9.


28

Table 3-1. Standard Software Functions

Function Inputs Adjustable Constants Outputs

AVR Ramp Auto Increase (RF1@IN)Auto Decrease (RF1@DC)Manual Active (RF1@VE)Go to Preset (RF1@3E)Track Enable(RF1@T2)Track Value(RF1@2E)

High limit (RF1THO)Low limit (FR1TLO)Ramp rate (RF1NRT)Preset value (RF1@T3)Track lag (RF1WLG)

Reference out

AVR Setpoint Frequency (ASP@FQ)React. Cur.(ASP@IQ)REF Out (ASP@RO)UEL Out (ASP@UE)PSS Out (ASP@PV)Auto/Man (ASP@AC)Extra Input (ASP@EX)PT Fail (ASP@PT)Gen Volts (ASP@VM)PSS Armed (ASP@PC)Gen Watts (ASP@WT)PT Fail Reset (ASP@PR)

ASP Limit High (ASPHLM)V/Hz Gain (ASPVHZ)RCC Gain (ASPRCC)PSS High Watt (ASPHIW)PSS Low Watts (ASPLOW)

AVR RefAuto ActiveMan ActivePSS ActiveV/Hz ActiveUEL ActiveSetpoint In LimitLatched PT Fail

FCR FCR Setpoint FCR@SPFCR Enable FCR@ENFCR Alternate SetpointFCA@SPFCR Alternate EnableEFA@EN

FCR Prop Gain (RGKC0)FCR Integral Gain (IRWIC0)Alt FCR Prop Gain (IRGKA0)Alt FCR Integral Gain(IRWIA0)

FCR OutputILOP0

AVR Generator Volts (AVR@FB)FVR Output (AVR@TV)AVR Ref (AVR@SP)Manual Active (AVR@TC)Bridge Fire Enabled(AVR@ZC)

High Limit (AVRPLM)Low Limit (AVRNLM)Prop. Gain (AVRPGN)Integral Gain (AVRIGN)Tracking Gain (AVRTGN)

AVR OutAVR In LimitAVR Error

FVR Ramp Manual Increase (SS)Manual Decrease (SS)Auto Active (RF2@2E)Go To Preset (RF2@3E)

High limit (RF2TH0)Low limit (RF2THL)Ramp rate (RF2NRT)Preset value (RF2@T3)

Reference Out

FVR Field Current (IFE)AVR Out (EFR@TV)FVR Ref (EFR@SP)Auto Active (EFR@EN)Bridge Fire Enabled(MPWRENAB)

FVR Turn Off (FLDZVL)Tracking Gain (FLDTGO)Proportional Gain(FLDPGO)Integral Gain (FLDIGO)

FVR Out


29

Table 3-1. Standard Software Functions - Continued

Function Inputs Adjustable Constants Outputs

UEL Watts (RA1@I1)Gen. Volts(@INPUT)VARs (R2@FBO)

VARs Ref. 0 (FGENYO)Watts Ref. 1 (FGENX1)VARs Ref. 1 (FGENY1)Watts Ref. 2 (FGENX2)VARs Ref. 2 (FGENY2)Watts Ref. 3 (FGENX3)VARs Ref. 3 (FGENY3)Watts Ref. 4 (FGENX4)VARs Ref. 4 (FGENY4)Prop. Gain KP (R2KFBO)Integral Gain KI (R2WI_0)High Limit (R2LMPO)Low Limit (R2LMNO)

UEL Output

OEL Field Current(CURRENT)

High Limit (CRLMHI)Low Limit (I2tAFL)FCR Preset (PIT@RS)Inst. Overcur. Lim (PITPU)IIT Limit (PITLM)FCR Pos. Limit (FCRPLM)IIT Cooling Mult. (I2tCMT)

OEL Act(FLDMOD)IIT Acc(PITIACCM)

Firing Block FVR OutFCR OutIOC ActiveStart/Stop

Retard Limit Firing Code


30

Figure 3-1. Software Overview


31

Figure 3-2. Automatic Voltage Regulator (AVR) Ramp

Figure 3-3. Automatic Voltage Regulator (AVR) Setpoint


32

Figure 3-4. Automatic Voltage Regulator (AVR)

Figure 3-5. Field Voltage Reg (FVR) Ramp


33

Figure 3-6. Field Regulator (FVR)

Figure 3-7. Under-Excitation Limit (UEL)


34

Figure 3-8. Over Excitation Limit (OEL)


35

Figure 3-9. Firing Block


36

Notes:


37

CHAPTER 4

SOFTWARE CONFIGURATION AND SCALING

4-1. INTRODUCTION

The software to configure various regulators,metering, and protective functions within theEX2000 PWM regulator operates on a count systemrepresenting actual feedback values. Thesefeedbacks are generated by current transformers,voltage transformers, and dc shunts. The signalsmay pass through isolators and amplifiers. Theseanalog signals are transformed to digital signals bymeans of voltage controlled oscillators.

The regulator controls use standard normalizedvalues to represent the variable being monitored orregulated. This enables the use of software that, to alarge extent, is not application dependent. Forexample, the automatic voltage regulator (AVR)controls the generator terminal voltage based on asetpoint chosen by the operator. For any machine, 1per unit (or rated terminal voltage) is defined withinthe AVR to be 20000 counts. If the operatorchooses to set the terminal voltage at rated then thereference to the AVR is 20000 counts. The voltagefeedback counts are compared to this reference togenerate an error signal and the appropriate controlaction takes place to maintain the feedback counts at20000.

The actual generator terminal voltage beingregulated is not referenced at this control level. It istherefore necessary to ensure that the feedbackcounts seen by the regulators are adjusted to providethe standard number of counts when the generator isoperating at rated. This is referred to as scaling.

An EX2000 system can be constructed several waysto accommodate customer system requirements. Forexample, the regulator can be fed from thepermanent magnet generator or from an auxiliarybus. It can be a brushless regulator or an SCTcontrol winding regulator. The controls are set tomatch the hardware used. This is known asconfiguration.

4-2. CONFIGURATION AND SCALINGEXAMPLE

The following section shows how scaling isperformed using example generator data. Theexample system is configured as a Brushless exciterregulator fed from a PMG with a 125 V dc batterybackup. There is also a single set of generatorpotential transformers (PT)s and no line PTs. Thescaling may not apply to all EX2000 applications.Contact GE Motors and Industrial Systems beforechanging any EE Values.

Even though the EX2000 PWM is a brushlessregulator and as such, operating data from thegenerator field is not readily available to theregulator, the generator information listed is criticalto the overall operation and performance of theregulator and excitation system. Assumptions madein the AVR and exciter field regulators are basedupon the available generator data.

4-2.1. Example Generator, Exciter AndRegulator

The example generator, exciter, and regulator datain this chapter is as follows:

4-2.1.1. GENERATOR DATA:

KVA 100000Frequency 60 HzVolts 13800PF 0.85Cold Gas Temperature 40 °CRated Stator Amps 4184Amps Field No Load 313Amps Field Air Gap 281Amps Field Full Load 846Amps Field Ceiling 1360Field Open Circuit Time

Constant (T’do) 5.615 secField Open Circuit Subtransient (T’’do) 0.022 sec


38

Field Winding Resistance 0.199 ohms at 25 °CVolts Field Full Load 136Station battery volts 125 V dcPT Ratio 14400/120Current Transformer (CT) Ratio 8000/5

4-2.1.2. EXCITER DATA:

kW 268Volts 300Rated Exciter Output Amps 893Amps Field Air Gap (exciter) 1.712Amps Field No Load (exciter) 3.52Amps Field Synch Imp.(exciter) 6.236Amps Field Full Load (exciter) 9.54Amps Field Ceiling (exciter) 15.45Exciter Time Constant (T’do) 0.35 secField Winding Resistance (exciter) 4.871 ohms

at 25 °C

4-2.1.3. REGULATOR DATA:

DC shunt 10 A = 100 mvDynamic Discharge Resistor 17.0 ohmsDynamic Discharge Resistor

Rated Amps 6.0 ACharge Control Resistor 2.0 ohmsVoltage Doubling NoDC Link Expected Volts

from PMG 137Maximum Expected DC

Link Volts 360

4-3. GENERAL CONFIGURATION

Throughout this example, the software nomenclatureis defined as follows:

EE.XXXX (ABCDEF), where "XXXX" representsthe software address location and "ABCDEF"represents the software address name.

There are many parameters that are set in theEX2000 PWM which are not discussed in thismanual. Many of them are used to set upconfigurable parameters such as the Status S datalink, communication, and so on. These are fixedparameters baud rates, displays configuration,keypad configuration for all EX2000 PWM

applications and should not be changed or needchanging on any requisition. If any parameters notdiscussed in this manual are in question, contact theproduct service group of GE Motors and IndustrialSystems or the local GE service organization foradvice.

The following are general configuration adjustableparameters (EEPROM) used to direct signals andhelp make the configurable blockware function as abrushless regulator.

Generator Model Jumper EE.3850 (GMJMPR)

EE.3850.1 Used to simulate PT failure insimulator mode. Normally set tozero.

EE.3850.2 Selects slip source for PowerSystem Stabilizer (PSS) Theexample has no PSS

EE.3850.3 Selects extra PT source forcalculation of PT failure. Can onlybe from PTCT board for EX2000PWM. Set to (0).

EE.3850.4 Generator model type. Can be static(0) or rotating (1). Brushlessregulator is rotating.

EE.3850.5 Selects 50 hz (1) or 60 hz (0) systemfor simulator and normal operation.Example is 60 hz.

EE.3850.6 Selects terminal (0) or separatelyfed (1)inputs for bridge. EX2000PWM is separately fed.

EE.3850.7 Selects whether the extra PT is usedfor calculations if a PT failure isdetected. (1) is yes, (0) is no. NoPT failure detection available in theexample.

EE.3850.8 Selects location of extra PT input.Line side (1) of 52G breaker orgenerator side (0). Example doesnot have extra PT input.

EE.3850.9 Select if PT failure detection isalways (0) or only with 52G closed(1). No PT fail detection inexample system. Set to zero.

EE.3850.10 Use maximum of PT feedbacks forcalculations. (1) is yes, (0) is no.No for example.


39

EE.3850.11 Adjusts simulator for 60 hz (0) or50 hz (1)

EE.3850.12 Sets LOE calculation for high gain(rev. G1B) PTCT board for LOEcalculations. All new EX2000PWM use high gain PTCT inputs.Set to (1)

EE.3850.13 Adjusts PTCT board inputs for Rev.A (0) or Rev. B (1) board.

Configuration Jumper EE.589 (ECNFIG)

EE.589.0 Selects IFG feedback to be fromSHPL on GDDD (1), IA2PL fromGDDD (2) or none (0). Set to 2 forEX2000 PWM

EE.589.2 Selects IFE feedback to be fromSHPL on GDDD (1), IA2PL fromGDDD (2) or none (0). Set to 1 forEX2000 PWM

EE.589.4 Selects VFG to be from APL/BPLon GDDD board (1), IA1PL onGDDD board (2) or none (0). Set tozero for EX2000 PWM.

EE.589.6 Selects VFE to be from APL/BPLon GDDD board (1), IA1PL onGDDD board (2) or none (0). Set toone for EX2000 PWM.

EE.589.8 Selects field regulator feedback tobe either VFG (0), VFE (1), IFG (2)or IFE (3). EX2000 is a currentregulator for the exciter field. Set tothree.

EE.589.10 Selects source for Var.105 to beeither IFG (0) or IFE (1). Set to 1for EX2000 PWM.

Other general configuration parametersimportant to the operation of an EX2000 PWMregulator

EE.550 Identifies product type. ForEX2000 hardware select 4.

EE.556 Identifies hardware feedback board.For EX2000 PWM select GDDDboard 2.

4-4. FEEDBACK SCALING

As a brushless regulator, there are a limited numberof feed back signals from the generator available tothe EX2000 PWM. These are potential transformersand current transformers monitoring the statoroutput, a shunt feed back from the exciter field, andexciter field voltage. Main generator field currentand voltage are not commonly available for displayor control on a brushless generator. The followingsections will detail the common feed back signalsand the scaling used in the EX2000 PWM.

4-4.1. Generator Feedback

The PT and CT signals to the EX2000 PWMregulator are isolated by the PTCT board. Thevoltage signals generated by the PTCT are sent tothe TCCB transducer board. Here voltagecontrolled oscillators (VCO) translate the analogsignals into digital counts.

The PTCT board will accept one set of three phaseCT inputs from the main generator stator currenttransformers. These CT’s must have a nominal 5amp secondary and phase A and C are required forcorrect operation of the EX2000 PWM regulators.Phase B CT input is not required and is not used bythe controls. EE.3840 CT_ADJ is used to accountfor off nominal CTs. The scaling for this EE settingis calculated as equal to 20480/(actual 1 pu CTsecondary amps)

For the example generator data: EE.3840 =20480/(4184*5/8000) = 7832

The PTCT board also accepts up to three sets ofgenerator voltage transformer inputs. These inputsare three phase inputs with a nominal secondaryvoltage of 120 V ac. Two of the inputs are forgenerator voltage before the synchronizing breaker.These two PT inputs should both be on the sameside of the generator step up transformer. The thirdinput can be used for a line side of thesynchronizing breaker voltage input. The scalingfor this EE setting is calculated as equal to491520/(actual 1 pu PT secondary volts)


40

For the example generator data: EE.3841 =491520/(13800*120/14400) = 4274

4-4.1.1. POTENTIAL TRANSFORMERFAILURE DETECTOR (PFTD) OPERATION.In the example system only one set of PT inputs arespecified. The second set of generator side PT’s canbe used for an optional Potential TransformerFailure Detection (PTFD) function. The generatorPTFD operates by comparing the sum of theabsolute counts for V12 and V23 signals (generatorPT signals) with the sum of the absolute countsrepresenting the extra PT input signals VX12 andVX23.

The 1 pu secondary voltages from these two sourcesdepends on the transformer ratios used. A scalefactor PTFDSC EE.3835 is used to null the signaldifference that could exist. The resulting magnitudedifference is filtered and the absolute value iscompared to the failure detection level set byEE.3837 PTFDVL. Under normal conditions thedifference between the two sums should beapproximately zero. If this absolute difference isgreater than the value set by PTFDVL EE.3837 thena PT FAIL FLT.488 is generated and VAR.1166EXPTFD becomes true. This variable is sent to theexcitation autosetpoint block input ASP@PT and, iftrue, forces a latched transfer to the manualregulator.

The PTFD can be disabled off-line by settingEE.3850.9 GMJMPR.9 equal to 1. The PTFDdetector can be tested using the simulator by settingGMJMPR.1 equal to 1 to simulate loss of V12 PTsignal.

Setting EE.3850.9 GMJMPR.7 equal to 1, the extraset of PTs can be used for all calculationsdownstream from the PT failure detector software.

4-4.1.2. PTFD SCALING. Parameter PTFDSCEE.3835, PT failure scale adjust, is used to null anysignal difference existing between V and X PTs. Ifa second PT for failure detection were supplied,then set EE.3835 = 4096 * (1 pu V PT secondaryvolts/1 pu X PT secondary volts).

In most cases, the second set of PT inputs would bethe same secondary as the first and the default valueof 4096 would be used

4-4.1.3. PTFD DETECTION LEVEL. The failuredetection level is set using PTFDVL EE.3837. It istypically set to approximately 50% of nominal (120V) PT signal (loss of half the voltage of one phase).

For the example system, EE.3837 = 0.5 * 2048 *(115/120) = 981. In the formula, 2048 represents acomplete loss of a PT signal and 115 is the actual 1pu PT secondary volts.

A PT failure detection causes automatic transfer tothe field (or manual) regulator. This regulatorcontrols field current level and does not look atgenerator terminal voltage. This is the only faultthat initiates automatic transfer to the manualregulator. It is not possible to transfer back to theAVR until this latching fault is cleared. Theoperator interface should indicate when a PTFD hasoccurred. A reset signal must be sent to reset thePTFD. A soft reset of the core is necessary to clearthe fault display from the LDCC board once the PTfeedback problem is fixed.

4-4.1.4. P.T.U.V. If a second set of generatorPT’s is not provided then the PTFD schemedescribed above can not be used. In this case thePTFD function is disabled by setting EE.3837 to65,535 and protection is provided by pointingASP@PT at VAR.1182 EXPTUV. In the event ofloss of one phase or complete loss of generatorvoltage signal as measured by the TCCB board, andafter a time delay specified in EE.3834 PTFDT1.EXPTUV will become true, forcing the control intomanual regulator mode.

4-4.2. Bridge Voltage Feedback

The bridge (regulator) dc output voltage feedbacksignal is fed via APL-5 and BPL-6 from the IAXSboard to the GDDD board. A voltage controlledoscillator on the GDDD board converts this analog


41

signal to a frequency and digital counts. JP1 on theGDDD board is set per the maximum expected dclink voltage. For units not employing the voltagedoubling feature of the EX2000 PWM regulator,this is normally 360 volts. The example systemdoes not use voltage doubling.

The dc link voltage feedback signal is fed to theGDDD board via the DCPL -1 and 2 connections onthe IAXS board. Again, JP2 on the GDDD board isset to the maximum expected DC link voltage.

EE.612 VDCMAX sets the 1 pu count level (20000)equal to 360 or 604 volts for scaling of both the DClink voltage and DC output voltage. JP3 on theGDDD board sets the operation level of the dynamicdischarge firing circuit. The selection of JP3 is alsobased upon the maximum expected dc link voltage.JP1, 2 and 3 on the GDDD board should all be set tothe same settings.

4-4.3. Bridge Current Feedback

The EX2000 PWM regulator field current feedbacksignal is from shunt SHA and is fed to the GDDDboard via connections SHPL-1 and -2. This input isscaled using EE.1505 CFISF0. This trims the gainof the VCO to achieve 5000 counts at 1 pu bridgecurrent. The scaling for this EE setting is calculatedas EE.1505 = 32768*(shunt rating)/(regulator ampsfield full load). For the sample system, the shuntrating = 10 A for 100 mv. The exciter AFFL ratingis 9.54 A.

Set EE.1505 = 32768 *(10)/(9.54) = 34348

4-4.4. Feedback Offsets

Due to the tolerance limits of the op-amps andVCOs that provide the EX2000 PWM feedbacks, itis possible that positive or negative offsets mayoccur with zero signal feedback. The actual offsetsproduced are dependent on the actual hardware andmust therefore be zeroed at startup. The bridgeoutput voltage, dc link voltage and shunt feedbackare adjustable using the following feedback offsets.

EE.1508 VF1OF0 is used to zero the VFB1 bridgevoltage feedback offset. With no bridge output,variable 1014 should be read using diagnostic test31. This count value multiplied by the constant -1141 and divided by the scale factor value in EE.612VDCMAX then becomes the value in EE.1508.

For example, with power on the bridge but thebridge not firing, monitor VAR.1014 (assumingVFE is the selected feedback) for any zero offset.Assume the offset found was approximately 80counts. Set EE.1508 = (80*-1141)/360 = -253.Enter this value and continue to monitor VAR.1014to verify that the offset is now zero.

EE.1510 CF1OF0 is used to zero the CFB1 bridgecurrent feedback offset. With no bridge output,variable 1016 should be read using diagnostic test31. This count value multiplied by the constant21475 and divided by the scale factor value inEE.1505 CFS1F0 then becomes the value inEE.1510.

For example, with power on the bridge but thebridge not firing, monitor VAR.1016 (assuming IFEis the selected feedback) for any zero offset.Assume the offset found was approximately -100counts. Set EE.1510 = (-100*21475)/34348 = -62Enter this value and continue to monitor VAR.1014to verify that the offset is now zero.

EE.1513 VDCOF0 is used to zero the dc linkvoltage feedback offset. Since dc link voltage isrequired for control power, this offset must be madewith dc link voltage present. VAR.1018 should beread using diagnostic test 31. The dc link voltageshould be read on the IAXS board connection pointsPL and NL. This measured voltage will then beconverted to counts. The converted measuredcounts minus the count value in VAR.1018 thenbecomes the value in EE.1513.


42

For example, with power on the bridge but thebridge not firing, monitor VAR.1018. Assume it is7825 counts. Then assume the measured value ofthe dc link is 137 volts. Converting the measuredvoltage to counts gives 137/360 * 20000 equals7611. Set EE.1513 = (7611-7825) = -213 counts.Enter this value and continue to monitor VAR.1018to verify that the offset is now zero.

4-4.5. Instantaneous Overcurrent Trip

An instantaneous overcurrent trip occurs if thebridge current, as monitored by SHPL (CFB1),exceeds the threshold set by EE.1518 IOCTROwhere 5000 counts = 1 pu Set EE.1518 = 25000 (5pu) with EE.1517 IOCTDO = 0 for no time delay.

4-5. REGULATOR SCALING

There are several regulators and limiters available inthe EX2000 PWM. The applicable one-line orsystem ordering documents will detail whether ornot all or any of these are supplied on a givenrequisition. Generally the AVR, FVR, and OELregulators are supplied as standard. The UEL, RCC,and V/hz limiters are also generally standardfeatures. PSS and VAR/PF controllers are typicallysupplied as options.

4-5.1. Automatic Voltage Regulating System

The primary purpose of the automatic voltageregulator (AVR) is to control the generator terminalvoltage according to a chosen reference. Theterminal voltage can then be modified by variouslimiter and regulator functions.

4-5.1.1. AVR OPERATION. The EX2000 PWMis designed to be started in AVR. The exciter can bestarted in AVR mode with the generator operatingfrom 20 to 100 Hz. To prevent initial overshoot, theintegrator is held at the preset value until 95%voltage is obtained. For a normal bandwidth AVR,this also means forcing the regulator to its maximumoutput until 95% of terminal voltage is reached. Ifthe speed of the generator is below rated when theregulator is started, the V/Hz limiter will hold down

the terminal voltage and regulator output such thatthe volts per hertz ratio specified in the AVRcontrols is maintained.

4-5.1.2. REF1 OPERATION. The selected(unmodified) reference originates in the INC/DECreference block REF1 (see Figure 3-2). The initialreference used in the EX2000 PWM is a presetvalue normally set for 1 pu generator voltage. TheREF1 output tracks this value when a start is givento the regulator. During this initial operation theRAISE and LOWER controls are ignored.

Once the startup operation is complete, the referencecan be changed by selecting RAISE or LOWERfrom the operator station with the regulator inAUTO regulator. When off-line, selecting RAISEor LOWER controls the generator terminal voltageover a range set in REF1 (and the autosetpointblock). This range is normally ±10% of ratedterminal voltage. When on-line, selecting RAISE orLOWER increases or decreases the generatorterminal reactive voltage and/or the power output ofthe generator. The more stiff the connection to thepower system (lower impedance tie) the less thegenerator terminal voltage is able to change.

An optional volt ampere reactive/power factor(VAR/PF) controller can also control the output ofthe REF1 block. While under control of theVAR/PF controller, the slew rate of REF1 is slowedto an alternate ramp rate, and the operatorRAISE/LOWER inputs are ignored.

When the exciter is operating in manual, theautosetpoint reference REF1 tracks a valuerepresenting the sum of ASP@VM (normallygenerator voltage) and the reactive currentcompensation signal. While REF1 is tracking thisvalue, the INC/DEC commands from the operatorstation are ignored in the REF1 block. The outputof REF1 in VAR.282 REF1OUT0 is passed to theautosetpoint block (EXASP).

4-5.1.3. REF1 SCALING ANDCONFIGURATION. REF1 tracks target [email protected] without delay during startup. It is normallypointed to a value of 20000 counts for 1 pugenerator voltage. For 1 pu generator voltage setEE.3402 = 19.


43

During startup, a quick store register can be used topreset the terminal voltage to a value other thanrated. This register can contain a count valuerepresenting the desired preset voltage. RF1@T3should then be pointed to this address. For example,during startup, if the desired preset voltage is 12.5kV on a 13.8 kv machine, the reference presetcounts required is 12.5/13.8 * 20000 = 18116counts.

Quickstore EE.95, currently an unused register, canbe used to store this value. Then, point EE.3402(RF1@T3) to EE.95 instead of the normal EE.19location.

The range of the AVR is set using EE.3414 RF1TH0(upper limit) and EE.3412 RF1TL0 (lower limit).Set this to provide a range of ± 10% of ratedgenerator voltage. Set EE.3414 = 18000 andEE.3412 = 22000.

To select the ramp rate of the AVR setEE.3400.6 = 0 for a normal INC/DEC scale controlsetting of 1/10 bits/sec. The time to ramp across theAVR range is set by the normal INC/DEC rateEE.3421 RF1NRT.

The range of the AVR = (22000-18000) = 4000.The desired time to cover this range is 60 secondstaking into account the setting of EE.3400.6. SetEE.3421 = (4000/60) *10 = 667.

4-5.1.4. AUTOSETPOINT BLOCK. Theselected reference from REF1 enters theautosetpoint block (EXASP) as the main autoreference setpoint. This reference can now bemodified in the autosetpoint block by variousstandard and optional regulators and limiters. Inaddition to the REF1 input the ASP block receivesfeedback variables for reactive current, generatorterminal voltage, generator frequency, the output ofthe under excitation limiter, and generator realpower if a power system stabilizer (PSS) is used(see Figure 3-3).

Automatic regulation is enabled through theoperator station or the A/M selector button on theLDCC board programmer keypad. When auto isactive, VAR.953 ASPAUTOA will be true. TheASP block also has an input from the PTFD (or

PTUV). When a PT failure is detected, regulation isswitched to the MVR. ASPAUTOA becomes falseand remains latched in that state until the PTfeedback problem is corrected, the core is soft reset,and the PTFD reset button on the operator station ispushed to permit selection of AUTO operation.Configuration jumper EE.589 selections candisabled the PTFD while off-line.

The ASP block contains a summing junction,minimum value gate, and a positive output limiter.The summing junction adds the output of REF1, theUEL regulator output, the PSS regulator output (ifpresent), and an extra input ASP@EX. This extrainput can be used to insert a test signal. The RCCcompensation signal is subtracted in the summingjunction.

The output of the summing junction feeds aminimum value gate where it is compared with aV/Hz limit signal proportional to the generatorfrequency by an amount set in EE.3789 ASPVHZ.The minimum of these two references is used as thereference sent to the regulator. The maximumoutput is limited to a value set in EE.3790ASPHLM. If the reference used by the regulator isthe V/Hz limit and the exciter is in auto, thenVAR.958 ASPVHZA is set true and an indication isgiven that the exciter is in V/Hz limit.

If a positive value is input to the summing junctionfrom the UEL and the exciter is in auto, thenVAR.959 ASPUELA is set true and an indication isgiven that the exciter is in UEL. The output of theAVR setpoint block VAR.158 ASPAVRSP is sentto the AVR block as the regulator reference signal.

4-5.1.5. AUTOSETPOINT BLOCK SCALINGAND CONFIGURATION. For the example systemthe V/Hz limiter will be set to 110%. Set EE.3789,the V/Hz gain, to 282 (256 = unity) For 50 Hzapplications, multiply EE.3789 by 6/5.

The ASP High Limit is set in EE.3790 ASPHLM.This is generally set for 110% of rated or 22000counts. For 50 Hz applications, multiply EE.3790by 6/5.


42

4-5.1.6. AUTOMATIC VOLTAGEREGULATOR (AVR) BLOCK. The AVR is aproportional plus integral regulator that comparesthe generator terminal voltage feedback (derivedfrom the V12 and V23 generator PT signals) with areference from the auto setpoint block to producean error signal. This error signal, VAR.156AVRERROR, is fed to the PI regulator. If theEX2000 PWM is in automatic regulator, the outputof the AVR, AVROP VAR.157 is then fed to theinner loop field regulator. The AVR output islimited to approximately 2 pu field current so as tonot overdrive the exciter. The output of the AVR ispassed through the field regulator to cancel theimpact of the additional time constant of the rotatingexciter. By doing this, the calculations and settingsof the various regulator limiters, (UEL, V/Hz, OEL)can be set using the same rules as a terminal fed orbus fed excitation system. Tuning of regulators inthe field is thus minimized.

The AVR is preconditioned to a valuecorresponding to AFNL at startup. The initial valueof AFNL used could be an estimated value. Afterthe initial startup, when a precise value of firingcommand counts for AFNL is known, thepreconditioning value stored in EE.92 can beadjusted accordingly.

When the precondition input AVR@ZC is true, theAVR output follows the preconditioning valueAVR@ZV. If AVRJMP.0 = 1 the integratorcontinues to follow AVR@ZC until AVRERROR isless than 5% (1000 counts on a 20000 base). If, inaddition to AVRJMP.0 = 1, AVRJMP.1 also = 1then the output of the AVR is forced to maximum asset in EE.3772 AVRPLM until the AVRERROR isless than 1000 counts. If the exciter is in MANUAL(ASPMANUA true), the AVR tracks the output ofthe field regulator FLOPO VAR.1004.

The AVR integrator has anti-windup protection thatzeros the error feeding the integral gain if either:

a. The output is in positive limit or if theEX2000 PWM regulator is in FCR and theerror signal feeding the regulator is positive.

b. The AVR output is in negative limit or infull retard and the error signal feeding theregulator is negative.

4-5.1.7. AVR SCALING ANDCONFIGURATION. The AVR response is not setfor optimum speed, but for acceptable performancewithout risking instability due to local modeoscillations. This setting is considered to be anormal bandwidth regulator. A high bandwidthregulator is used when a high gain fast responseAVR is required. The example assumes a normalbandwidth regulator. If a high bandwidth regulatoris chosen, then the high bandwidth settings for theUEL regulator should be used also.

AVRJMP EE.3759.0 is set to 1 for AVR output tofollow AVR@ZC until regulator error is less than1000 counts. Set at 1 for a high bandwidth exciteralso.

EE.3759.1 is set to 1 on a normal bandwidth exciterto hold AVROP in ceiling until AVRERROR is lessthan 1000 counts. Set to zero for a high bandwidthexciter.

AVRPLM EE.3772 is the positive limit for AVRoutput. Normally set to 10000, which isapproximately 2 pu current for the exciter field.

AVRNLM EE.3773 is the negative limit for AVRoutput. Set to 0

AVRTGN EE.3770 is the AVR tracking gain. Thissets the time delay for the AVR to track the outputof the field regulator while in manual regulator. SetEE.3770 = 5 (where 100 = 1 rad/sec) for a 20second tracking filter.

The following is an example of setting the AVRregulator for an EX2000 PWM regulator withnormal bandwidth.

Prior to startup, the AVR output is preset to the noload exciter field current level. This effectivelywipes out overshoot problems when starting in theautomatic regulator.


43

AVR@ZV EE.3764 points to EE.92 In EE.92, theRUN2RF storage register stores the firing commandcount value necessary to produce 80% exciterAFNL. In the example, exciter AFNL was 3.52 Adc.

Set RUN2RF EE.92 to a FIRCMD = 0.8 * AFNL*5000/AFFL = 0.8*3.52*5000/9.54 = 1476

4-5.1.8. AVR PROPORTIONAL GAIN. Theproportional gain of the PI regulator is set asfollows:

1. Determine the transient gain requirements ofthe system.

2. Calculate the proportional gain which isdirectly proportional to the transient gain. For thenormal bandwidth regulator, set the transient gain to4*T’do (the open circuit field time constant) with 20as a default minimum for new gas and steamapplications. A high bandwidth regulator should beset for a transient gain of 100.

From the transfer function of a brushless EX2000PWM regulator, the relationship betweenproportional and transient gains is:

Transient gain = (Kp*20000 * Kex*AFFLex) /(VFAGgen*5000) where Kex is the gain of theexciter. The gain of the exciter is calculated as the(voltage out/current in) or ((VFFLgen at 100 C -VFNLgen at 100 C) / (AFFLex - AFNLex)). For theexample system, Kex is calculated to be (216-80.13)/(9.54-3.52) = 22.51.

VFAGgen is the air gap voltage which is determinedby reading IFAG from the machine estimated air gapline at 1 pu armature voltage. The examplegenerator has IFAG of 281 A dc. The rated fieldresistance Rf@rated temp is defined as 100 C. TheRf@100C was not given and is thereforeextrapolated from Rf@125C to give Rf@100C =.256 ohms. VFAG = .256 * 281 = 72 V dc.

Solving for Kp gives Kp = (transient gain *VFAGgen*5000) / (20000 * Kex*AFFLex) =(20*72*5000) / (20000*22.51*9.54) = 1.67.

Set AVRPGN EE.3769 = 1.67 * 256 (where 256 =unity) = 429

4-5.1.9. INTEGRAL GAIN. Set Kp/Ki = 1 for alead time constant of 1 sec. For the example Ki =Kp = 1.67

Set AVRIGN EE.3771 = 1.67 * 100 (where 100 = 1rad/sec) = 167

4-5.2. Under Excitation Limiter (UEL)

The two basic problems with operating a generatorin the underexcited region of the capability curveare stator end iron heating and generator steady statestability limit. Stray flux in the end turn region of ahigh speed steam or gas turbine driven generator cancause large losses in the core end iron duringunderexcited operation.The steady state power stability limit indicates themaximum real power that can be delivered atconstant field voltage. The effect of the high initialresponse AVR is to substantially increase the steadystate stability limit. The generator must beconstrained to operate in the underexcited region inan area where the unit would be stable if a transferwere made to the field regulator.

The thermal limit is usually more restrictive than thepower stability limit. The default scaling of theUEL curve described is based on the generatorcapability curve. The intent is to protect thegenerator from end iron heating effects by settingthe UEL approximately 10% above the underexcitedreactive capability curve. The 10% is chosen to givesufficient safety margin.

The stability limit is a function of the network towhich the generator is connected. The customer isresponsible for system stability protection settings.If the customer supplies UEL curve points, enterthose values instead of the values from the methoddescribed.

4-5.2.1. UEL OPERATION. This sectiondescribes the UEL operation which is performed bya combination of standard blocks (see Figure 3-7).The capability of a generator when plotted on areactive power versus real power plot changes asterminal voltage changes. This means that a numberof curves are required to provide protection over thenormal 10% terminal voltage range permitted by theAVR. If the real and reactive power signals are


42

normalized by dividing by the square of the terminalvoltage then the capability of the generator becomesa single curve.

The generator watts signal is first normalized bydividing by the square of the filtered voltage signal.The resulting normalized power is then filtered andabsoluted. This value is fed to the functiongenerator block where the normalized pu UEL curvehas been entered. The output of the functiongenerator block is the UEL curve pointcorresponding to that value of generator real poweroutput. This value then becomes the UEL limitallowed.

This UEL limit as read from the curve is normalizedVARs and must be multiplied by the square of thefiltered voltage signal to produce a VAR referencefor the proportional plus integral regulator. The PIregulator is enabled by an AND gate if 52G isclosed and the AVR is in control. It comparesmeasured generator VARs feedback quantity with areference limit derived from the UEL curve togenerate an error signal which feeds the regulator.

The output of the PI regulator block is fed to alimiter set to allow only positive outputs. This valueis then fed to the excitation autosetpoint blockASP@UE input. It is added to the existing AVRsetpoint to produce an increase in the excitationlevel sufficient to prevent the excitation decreasingbelow the level corresponding to the UEL limitcurve chosen.

4-5.2.2. UEL SCALING ANDCONFIGURATION. Configuring and scaling theUEL function involves setting the PI regulator forproper gain and time constants. It also includessetting the UEL curve based on the generatorcapability curve.

The UEL limiter uses process regulator #1. This is aproportional plus integral regulator. A PI regulatorhas the form:

Kp + Ki/s where Kp = proportional gain and Ki =integral gain (rads/sec).Only two sets of adjustments for the UEL regulatorare necessary. One for exciters using a normalbandwidth AVR and one for those customersrequiring a higher bandwidth, such as a fast

response/high gain AVR. The default setting isnormal bandwidth. The recommended settings areas follows:

NormalEE.5899 = 200 (Ki = 2 rads/sec)EE.5900 = 819 (Kp = 3.2)

HighEE.5899 = 200 (Ki = 2 rads/sec)EE.5900 = 410 (Kp = 1.6)

NOTE

Two EEPROM values are set becausethe command and feedback gains areindependently adjustable.

Steady state stability of the UEL can be verified byoperating the generator at various power levels thenslowly lowering the excitation to drive the generatorinto the limit curve. Dynamic closed loop responsecan then be verified by stepping the AVR setpointusing the excitation autosetpoint block extra inputASP@EX. A step of 1 or 2% is sufficient. If it isnot permissible to drive the generator into its truelimit curve then the curve could be reset at a saferlevel and the testing performed using this curve.

4-5.2.3. UEL CURVE. The UEL limit curve isobtained by using a general purpose backgroundfunction generator block. This is a five pointpiecewise linear function generator. The function isflat to the left of Y0, the first point, and to the rightof Y4, the last point. The X coordinates must bemonotonically increasing X0<X1<X2<X3<X4.

The coordinates are specified in counts, wheregenerator 1 pu watts = 5000 counts and generator 1pu VARs = 5000 counts. The underexcited portionof a typical generator reactive capability curve isshown in Figure 4-1.


47

Generator Data: 100000 k VA3600 RPM0.85 PF40 °C cold gas13800 V

1 pu power at unity power factor = 100 MW = 5000counts. This value was defined during primaryscaling of the generator voltage and currentfeedbacks. The EX2000 calculates watts and VARsfrom measured generator voltages and currents.

If the customer has not specified UEL settings, thefollowing recommended settings can be used:

Recommended X coordinates are at 0.3, 0.6, 0.9,and 1.2 pu MW. X = 0 is the X coordinate for Y0point and needs to be entered. This gives thefollowing values:

X1 = 0.3 pu = 0.3*5000 counts = +1500 = EE.2864(from the example curve this is equivalent to 30.0MW)




Next, the Y coordinates must be chosen. Thismethod selects Y values 10% above the ratedcapability curve to provide ample safety margin. Ifmore than one curve is given for different gastemperatures, use the rated curve. In the examplegiven this is 40 °C cold gas. From the chosencustomer reactive capability curve, read the VARs at0 power. This is -35 MVARs. Add 10% of ratedkVA (not 10% of the reading) to define the Y0point. Y0 = -35 + (10% * 100) = -25 MVARs. Thisvalue must now be changed to counts to store inEE.2872.

EE.2872 = (-25/100)*5000 counts = -1250 counts =Y0

Y1, Y2 and Y3 are obtained as follows:

Y1 = -40 MVARs + 10 = -30 = -1500 counts =EE.2865

Y2 = -35 MVARs + 10 = -25 = -1250 counts =EE.2867

Y3 = -17 MVARs + 10 = -07 = -350 counts =EE.2869

The final value Y4 is chosen differently. A straightline is drawn from the Y3 point through the 1 pu atunity power factor point to intersect the X = 1.2 pupower line. This gives Y4 = -2*Y3 = -2 * -350 =+700 counts = EE.2871. All this is based on theassumption that the 0.9 pu power point on thecapability curve yields a negative value and the finalsegment passes through rated k VA at unity powerfactor. The final point Y4 is chosen this waybecause this gives better coordination with loss ofexcitation protection.


48

Figure 4.1 UEL Curve

4-5.3. Reactive Current Compensator (RCC)

The RCC signal is used to compensate forinsufficient reactance between generators or whenthere is too much reactance. The RCC simulates areactance on the generator output. If reactivecurrent increases, the amount subtracted from theautosetpoint also increases. This lowers theexcitation voltage and therefore the amount ofVARs produced by the generator. It provides adrooping characteristic to insure that the loadreactive power is equally divided between paralleledmachines.

Generally this compensation is required if machinesare paralleled directly on the same bus. Ifgenerators are paralleled on the high side of theirgenerator step-up transformer, then sufficientreactance should exist between the generators sothat additional compensation is not required. Thefactory default setting is zero compensation.Determine the amount of compensation necessary

during initial startup. The compensation is set to theminimum required to ensure VAR sharing. Valuesof 3% to 6% reactance are usually sufficient.(Alternatively, EE.3791 ASPRCC can be set to anegative value to provide line drop compensationLDC).

RCC is set by EE.3791 ASPRCC, reactive currentgain. The range of this setting is ± 12.5%compensation. The setting for the +12.5%compensation is 32768 counts, or 2621.44 countsper percent compensation. If an RCC of 4%reactance is desired, set EE.3791 = 4*2621.44 =10486. If LDC is required, EE.3791 is set to anegative value. For a 4% line reactance, or linedrop compensation, set EE.3791 = -10486.


49

4-5.4. VAR/Power Factor Control

A VAR/Power Factor controller can be provided asan optional regulator in the regulator core. EitherVAR control where a constant generator VARoutput is maintained or power factor control where aconstant generator power factor is maintained can beselected. The two control actions are, of course,mutually exclusive. The PF/VAR controller can beconfigured to latch to the existing PF or generatorVAR output when the associated control action isinitiated.

The operator station is used to enable the PF/VARcontroller. The operator must adjust the generatorto the VAR output or PF that it is desired tomaintain. The appropriate operator station button isthen pushed to latch the output at the desired value.To release the control action, the same button ispushed a second time.

4-5.4.1. VAR//PF CONTROL OPERATIONAND CONFIGURATION. The PF/VAR controlblock uses the generator VARs and Watts as itsfeedback variables. These inputs are selected byEE.3718 PF@VAR, normally pointed to VAR.1153,generator VARs and EE.3719 PF@WAT, normallypointed to VAR.1152, generator watts.

The watt and var signals pass through low passfilters both of which are set by EE.3723 PFLPFW.A setting of 5 rad/sec is typically used (where 100=1r/s).

The filtered VAR signal is fed to a latch and thenegative input of the controller summing junction.The latch gets set when VAR control is selected.The input variable that controls VAR controlselection is set by EE.3717 PF@ENV. When thisvariable is true, VAR control is selected. The latchholds the value of VARs that was measured as thelatch was set. This latched variable is fed to aswitch. The switch is configured by EE.3720PFARK. If PFARK is set to 0, then the switch willpass the latched value of VARs to be regulated. IfPFARK is set at a non zero value then the generatoroutput VARs corresponding to this count value willbe maintained. This feature is typically not used.

The preset or latched VAR setting is fed to a secondswitch that will pass either the VAR or PF referenceto a summing junction depending on which controlaction has been selected. If the VAR setting waschosen, the VAR reference will be fed to thesumming junction where the actual VAR feedbackwill be subtracted to create an error signal. Thiserror signal passes through a deadband set byEE.3722 PFDEBD (5000 counts = 1 pu). Thedeadband setting should be chosen so that excessiveregulation does not occur while the required settingis accurately maintained. From the dead bandfunction a raise or lower signal is given to theexciter as required to maintain the value selected.The raise signal is PFVRAISE VAR.718 and thelower is PFVLOWER VAR.719.

The power factor controller functions in a similarfashion.

The VAR signal is multiplied by 32768 and thendivided by the watt signal. The resultant is thenormalized tan of the angle between watts and varswhere 32768 equals a tangent of unity (45 degrees).The resultant is filtered and then feeds a latch thatwill be set if the PF control function is selected.The output of the latch feeds a switch configured byEE.3721 PFVWTK. If PFVWTK is set to zero thelatched value is passed. If PFVWTK is set to a non-zero value, then the angle represented by the settingof EE.3721 will be regulated. A non-zero value istypically not used. The output of this switch ismultiplied with the actual generator watts anddivided by 32768. The resultant is the generatorVARs necessary to maintain the desired PF angle atthe new generator real power level. This becomesthe reference to the controllers summing junction,where an error signal is developed which causes theexciter to raise or lower the generator VAR outputto hold the desired power factor. The samedeadband setting applies to either the PF or VARcontroller.

NOTE

The algorithm does not calculate thecosine of the angle between thegenerator watts and vars so does notexplicitly develop a signal representingthe PF of the generator.


50

4-5.5. Field Regulator (FVR)

The FVR (manual) regulates the exciter fieldwithout reference to the generator terminal voltage.It is possible to configure the field regulator toregulate one of four variables. Either maingenerator field quantities IFG and VFG or exciterfield quantities IFE and VFE are selectable. For theEX2000 PWM, the field regulator is configured as acurrent regulator with IFE as the feedback variable .Normal regulator operation is in automatic voltageregulator with transfer to the manual regulator onlyoccurring as a result of losing the generator terminalvoltage feedback signal(s) due to PT failuredetection. The PTFD detector is disabled off-line incertain configurations. In this case, the field currentregulator (OEL) serves to limit the regulator outputto prevent overfluxing the generator. The operatorhas the capability to switch the exciter to manualregulation by an operator station command (seeFigure 3-5).

In automatic regulator, the field regulator receivesan input from the auto voltage regulator and acts asan inner loop regulator in an attempt to cancel theeffects of the time constant of the rotatingequipment. This allows for greater speed ofresponse when operating in automatic regulator.The AVR output is limited to 2 pu exciter fieldcurrent so as not to overdrive the regulator output.

4-5.5.1. REF2 OPERATION. Theincrease/decrease reference block normally suppliesthe field regulator reference to the core blockEXCOR. This reference block is identical instructure to the REF1 block used by the AVR.

During exciter startup, the output of REF2 tracks,without delay, the value pointed to RF2@T3. Thisis EE.91 RUN1RF register. RUN1RF is set to thecount value representing 80 percent of AFNLex.Normal increase/decrease control is disabled at thistime. If the exciter is in AUTO regulator and is notdetected to be in limit then the output of REF2tracks the variable pointed to by RF2@T2 which isnormally IFE.

The manual (backup) regulator tracks the fieldcurrent necessary to maintain the existing generatorterminal voltage. This tracking is delayed to avoidfollowing transient fluctuations or erroneous AVRbehavior. The ramp range is typically set for 70%of AFNLex to 120% AFFLex in 120 secs. The outputof the REF2 block is passed through a softwareswitch to the EX2000 core block and then to theMCP block as the field regulator adjust commandMFLDADJ VAR.165.

4-5.5.2. REF2 SCALING ANDCONFIGURATION. The present for the manualvoltage regulator RUN1REF EE.91 is set to a countvalue for *0% of AFNLex . Set EE.91 =(0.8*AFNLex*5000/AFFLex) = 1476.

The REF2 ramp high limit is set to 120% of AFFLex.

Set RF2THO EE.3444 = 1.2*5000 = 6000.

The REF2 ramp low limit is set to 70% AFNLex.Set RF2LO EE.3442 = .07*(3.52/9.54)*5000 = 1291

Typically the ramp time to cover this range is set for120 secs. Set RF2SLM EE.3446 = 0 for 1/10bit/sec rate and RF2NRT EE.3451 = ((6000 -1291)/120)*10 = 392.

Tracking delay, set RF2WLG EE.3447 = 50

4-5.5.3. FVR OPERATION. The field regulatoradjust command MFLDADJ VAR.165, whichnormally originates as the REF2 output or areference signal from the AVR, becomes thereference for the field regulator. This referencefeeds a summing junction. A feedback signalrepresenting IFE is subtracted from this reference togive an error signal (FLOPERR VAR.1003) for thePI regulator. The output of the field regulator(FLOPO VAR.1004) goes to a minimum value gatewhere it is compared with the field current regulatoroutput (ILOPO VAR.1002). The minimum of thetwo becomes the net firing command (FIRCMDVAR.1000).


51

4-5.5.4. FVR SCALING. The field regulator isset to cancel the effects of the time constant of therotating equipment by setting Kp/Ki = T’d0 of theexciter. With the loop gain set to unity, the transferfunctions of the inner loop reduce to be Ki =(2*pi*f*VFFL ex @75 C)/(Bridge Gain*5000). Thebridge gain is the actual DC link voltage divided by11775, maximum firing command counts.

The field regulator bandwidth for the EX2000 PWMregulator is chosen to be 10 Hz.

In the example system, VFFLex is 9.54 * 5.810 =55.4. The bridge gain is calculated as 137volts/11775 or .0116. Ki is calculated to be(2*pi*10*55.4)/(.0116*5000) = 60 Set FLDIG0EE.1551 = 60*65.536 = 3932 counts.

Since Kp/Ki was set to equal the time constant ofthe exciter, in the example system, Kp = Ki *0.35 or21. From this, EE.1550 FLDPG0= 21 * 256 = 5376counts.

FLDTGO EE.1547 sets the tracking filter for 2 secs.Set EE.1547 = 1/2 * 65.536 =33 (where 65.536 = 1rad/sec)

4-5.5.5. TRANSFER TRACKING METER ANDBALANCE. There is automatic tracking betweenthe manual and automatic regulators in eitherdirection with independent tracking delays. Abalance meter is normally provided on the operatorstation to show the amount of unbalance that existsbetween the regulators. While in the auto regulator,the unbalance is shown as the magnitude of exciterfield voltage unbalance that exists. If a transfer ismade at this time to the manual regulator, the exciterfield voltage jumps by this amount. While in themanual regulator, the balance is shown as thegenerator terminal voltage unbalance that exists.

4-5.6. Field Current Regulator (FCR)

The Field Current Regulator (FCR) is programmedwithin the MCP Block. This regulator is also aproportional plus integral (PI) regulator. The FCRhas a feature that allows for two sets of proportionaland integral gains to be entered. The FCR can thenbe switched between these two sets of gains through

a command (EFA@EN) to the Core Block. Thesetwo sets of gains are referred to as the primary fieldcurrent regulator and the alternate field currentregulator. The primary current regulator is enabledwhen FCR@EN EE.3706 is true. The alternatecurrent regulator is enabled when both [email protected] and FCR@EN are true.

The EX2000 PWM uses both of these currentregulators as an Overexcitation Limiter (OEL) tolimit exciter field current (and therefore maingenerator field current). The alternate FCR gainsand primary FCR gains are set exactly the same asthe field regulator gains since the field regulator inthe EX2000 PWM is configured as a currentregulator. The alternate current regulator is alwaysenabled unless an extended forcing condition isdetected, and is used as an instantaneous currentlimit. It has two setpoints, one for on-line and onefor off-line operation. The primary current regulatoris used as an inverse time limiter. Forcing isallowed for up to 10 seconds. If forcing ismaintained for 10 seconds, the alternate currentregulator is disabled with control switching to theprimary regulator. The primary regulator will thendrop the current to its on-line setpoint until theinverse time block activates and then control islimited to 1 pu exciter field current.

In the off-line situation, instantaneous exciter fieldcurrent is limited to 125% (or less) of AFNLex toprevent overfluxing the generator and connectedtransformers. On-line, the instantaneous current islimited to prevent heating (I2t) damage to the mainfield winding. However, it must allow proper fieldforcing for fault support before beginning its currentlimit function.

When either the primary or alternate current limitertakes control of IGBT bridge gate firing, an OELActive annunciation is displayed on or sent to theoperator interface. The control of bridge firing isdetermined by a function referred to as a minimumvalue gate. The field regulator cannot resumecontrol of bridge firing until the firing referencegenerated by AVR or FVR becomes lower than thefiring signal limit out of the current regulator. SeeFigure 3-8.


52

4-5.6.1. ALTERNATE FCR. Off-line, thealternate FCR limits the exciter field current toprotect against overfluxing the machine and anyconnected transformers. It is a backup V/Hz limitwith the actual V/Hz limiter in the excitationautosetpoint block serving as a primary limiter. On-line, the alternate current regulator serves to limitthe exciter field current to a level that protects therotating diodes in the brushless exciter.

The alternate field current regulator is enabledwhenever EFA@EN true. Until the generatoroutput breaker is closed, it will limit field current tothe value in EE.82, the off-line instantaneoussetpoint. Once the 52G breaker closes, the alternatecurrent regulator limit is switched to the value inEE.80.

As stated before, since the field regulator (FVR) isconfigured as a current regulator in the EX2000PWM, the proportional and integral gains for thealternate current regulator are identical to those inthe FVR.

4-5.6.2. ALTERNATE FIELD CURRENTREGULATOR SCALING. EE.1541 IRGKA0 isthe alternate FCR proportional gain. From thecalculations for the FVR in the example system, Kpfor the current regulator is 21. EE.1541 will then bethe same as EE.1550 = 256*Kp = 5376.

EE.1543 IRWIA0 is the alternate FCR integral gain.From the calculations for the FVR in the examplesystem, Ki for the current regulator is 60. EE.1543will then be the same as EE.1551 = 65.536*Ki =3932.

EE.1545 ILOPA0 is the alternate FCR preset value.In the EX2000 PWM, this is chosen to be 120% ofthe firing command for exciter field AFNL. For theexample system, this would be (1.2*VFNLex@25C*11775)/actual DC link voltage. EE.1545 =(1.2*3.52*4.871*11775)/137 = 1768 counts.

The off-line setpoint for the alternate currentregulator is stored in EE.82. This value is 125% ofAFNLex which for the example system would be1.25*3.52/5000 = 2306 counts.

The on-line setpoint for instantaneous current limitmust allow for forcing of the regulator duringsystem transients. Generally, calculations are madethat specify a ceiling from the exciter to support 2pu capability from the generator. The rotatingexciter diodes can be a limiting factor in what thison-line forcing capability is. In the EX2000 PWM,this current level is conservatively chosen to be themaximum of either 140% AFFLex or twice AFSIex

unless a higher value is specified by the originalequipment manufacturer. In the example system,1.4 * AFFLex = 13.356. Two times AFSIex = 2 *6.236 = 12.472. There is also a specified ceilinglimit of 14.45 amps. EE..80 will then be 15.45 *5000 /9.54 = 8097 counts. Before changing thisinstantaneous limit to a higher value, GE generatorengineering should be consulted.

An off-line protection block, PRITC, is provided asan instantaneous trip if the pickup setpoint isexceeded when the EX2000 PWM regulator sensesthe unit is off-line. It is set to a value above the off-line alternate field current regulator setting. If thislevel is reached, the regulator will immediately stopIGBT gating.

The PRITC block is set up for linear error with pureintegration (1 sec integration time). The pick upvalue is set to 1.25 AFNLex with the limit beingactivated as soon as the pickup level is exceeded.

Set PITJMP = 2. This sets the PRITC block forexcessive I*t function .

Set PITPU = 125% of AFNLex For the examplesystem 1.25*(3.52/9.54)*5000 = 2306 counts thePRITC begins to accumulate when PITPU isexceeded.

PITTRP is set such that the unit will stop gating at avalue of 160% of AFNLex. For the example system,this would be 645 counts. The trip setting is countsabove the pick up level for a trip.


53

4-5.6.3. PRIMARY FCR. The primary fieldcurrent regulator is used to limit main generatorfield current to a value so as not to exceed thethermal capability of the field copper. This limitmust be imposed on the EX2000 PWM outputcurrent into the exciter field in order to limit thecalculated main generator field current. Thesetpoints of the primary FCR are generally set to125% of AFFLex until the inverse time protection isenabled and then output current is limited to 1 puAFFLex.

Forcing on-line is allowed until the reference levelstored in a signal level detector (SLD1) is exceededfor 10 seconds or by a protection inverse time blockbeing in limit (PIT1LIM = true). The SLD level isset for 140% of AFFL. The protection inverse timeblock, PRIT1, is set to begin timing at 1.06 puexciter current and will activate the second level offield current at 1.25 pu after 60 seconds. The fieldregulator setpoint must be lowered below the levelof the field current regulators in order to releasecontrol from the FCR or FCA.

4-5.6.4. PRIMARY CURRENT REGULATORSCALING AND CONFIGURATION. EE.1540.IRGKC0 is the primary FCR proportional gain.From the calculations for the FVR in the examplesystem, Kp for the current regulator is 21. EE.1540will then be the same as EE.1550 = 256*Kp = 5376.

EE.1542 IRWIC0 is the primary FCR integral gain.From the calculations for the FVR in the examplesystem, Ki for the current regulator is 60. EE.1542will then be the same as EE.1551 = 65.536*Ki =3932.

EE.1548 ILOPP0 is the primary FCR preset value.In the EX2000 PWM, this is chosen to call for fullgating of the IGBT bridge. In the example system,this would be 11775 counts.

The high level setpoint for the primary currentregulator is stored in EE.83. This value is 125% ofAFFLex which for the example system would be1.25*5000 = 6250 counts.

After the PRIT1 block times out, the current willthen be reduced to the lower level setpoint for theprimary current regulator which is stored in EE.81.

This value is 100% of AFFLex which is equal to5000 counts.

For SLD1, the level that the input (IFE) is to becompared with is set in EE.152 SL1LEV. Thisvalue is set to 140% of AFFLex or 7000 counts.SLD1 pickup time delay EE.154 = 1000 (for 10second pickup)

The PRIT1 is an inverse time protection block. Thescaling is set on a per unit basis of AFFL. As allmachines are scaled to produce 5000 counts atAFFL then the values should not change on anindividual job basis. The PRIT1 block is scaled forI*t function with a sixty second leaky integrator.

Set EE.3749.0 PITJMP = 0 This sets the PRITblock for excessive I*t function (protect for fieldheating).

Set EE.3749.1 = 0 This sets the PRIT block with a60 second integrator.

Set EE.3751 PITPU = 5100 which is 102% ofAFFLex. The protection block will begin to integratewhen PIT@IN exceeds 102% AFFL.

Set PITDEL EE.3755, integrator leak gain to 16122counts. This setting allows the PRIT1 block tobegin accumulating but never reaches a point whereit will generate a trip. Essentially sets theaccumulation level to 1.06% of AFFLex.

A trip level can be set in PITTRP EE.3752. If a tripis used, a setting of 783 will cause a trip signaloutput in 120 secs at 112% AFFLex and 42.3 secs at125% of AFFLex.

A transfer level can be set in PITTRF EE.3753 If atransfer is used, a setting of 666 will cause a transferaction at 85% of the trip level.

PITDEL is set to 0 in EE.3755 so that pureintegration is used. A constant error signal willproduce a linear ramp of (PIT@IN -PITPU)counts/sec.


54

4-6. OPTIONAL FUNCTIONS SCALING ANDCONFIGURATION

Several optional functions are available with theEX2000 PWM regulator on brushless exciters.These include exciter field temperature calculation,field ground detection, and 4 - 20 ma outputtransducers. The requisition specific elementaryshould be consulted to determine which, if any, ofthese options have been supplied.

4-6.1. Transducer Outputs

The DAC1, DAC2, MET1, and MET2 analogoutputs are available for test purposes and aretypically used as the input reference for up to fourisolated 4-20 ma output transducers. The fouroutputs operate identically and are programmedsimilarly to the variables in Test 11. DAC1 andDAC2 have 12 bit resolution and are updated 720times per second. MET1 and MET2 have eight bitresolution and are updated 360 times per second.

Each output has two addresses (see Table 4-1).

• The @I address selects the variable to be output(EE100 = DAC1, EE102 = DAC2, EE104 =MET1, and EE106 = MET2)

The MX address is the maximum input value(EE101 = DAC1, EE103 = DAC2, EE105 =MET1, and EE107 = MET2)

• DAC1 and DAC2 can be offset by the valuesstored in DAC1OF and DAC2OF

For example, to bring up this function:

1. In the Parameter Mode, call up EE100-DAC1and EE101-DAC1MX (select EE.100).

2. Enter the signal to be monitored into EE.100.

Putting that RAM address in EE.100 produces thatsignal at the NTB/3TB board’s DA1 testpoint andDAC1 terminal (3TB-53).

DAC2, MET1, and MET2 function like DAC1.When a signal’s RAM address is loaded into theDAC and MET addresses, the signal is output on theNTB/3TB testpoints and terminal points listed inTable 4-1.

Typically, the DAC and MET outputs are assignedwith exciter volts (VFE), exciter amps (IFE),transfer volts, and occasionally exciter fieldtemperature. Consult the elementary for the specificrequisition to see which transducers are supplied, ifany. Typically, DAC1 is exciter field temp, DAC2is transfer balance, MET1 is IFE and MET2 isfiltered VFE.

Table 4-1. Diagnostic Mode Analog Output Points

Loaded into Address NTB TP Terminal Board Point

EE.100-DAC@1 &EE101-DAC1MXEE.108-DAC1OF

DA1 DA1, 3TB-53

EE102-DAC@2 &EE103-DAC2MXEE.109 DAC2OF

DA2 DA2,3TB-55

EE104-MET@1 &EE105-MET1MX

MET1 MET1, 3TB-54

EE106-MET@2 &EE107-MET2MX

MET2 MET2, 3TB-56


55

4-6.2. Ground Detector And Diode FaultMonitor

The EX2000 PWM is capable of interfacing with abrushless regulator field ground detector module.There are several different styles of grounddetectors available, some with multiple inputs to theEX2000 PWM, some with only one input. The mostcommon of these detectors is configured as follows.

This detector requires a 24 volt supply, typicallypassed through the EX2000 PWM cabinet. Thedetector returns three signals to the EX2000. Theseare a Ground Detector Malfunction alarm, a GroundFault alarm, and a Diode Fault alarm. These threeinputs are taken into the EX2000 PWM controls onthe NTB board at inputs V4VCO, FDBVCO, andREFVCO. These inputs are configurable voltagecontrolled oscillators which convert the analog inputto dc counts for use in the regulator.

The Detector Malfunction alarm signal is a nominal2 V dc when there is no fault present. This signal isscaled in the FBVCO and compared to a fixedreference in a signal level detect. A high signal(nominally 20 V dc) indicates a detectormalfunction.

The Ground Fault alarm is a nominal 10 to 24 V dcunless a ground fault is detected. Then the inputwill go to a nominal 2 V dc. This signal is scaled inthe V4VCO, compared to a fixed reference andpassed through a time delay such that the conditionmust persist for up to 10 seconds. It is ANDEDwith the inverse of the detector malfunction alarm.This prevents a false ground detection if the detectorhas indicated that it is not healthy. To preventinadvertent alarms when the unit is not operating,the ground fault detector is not activated until theEX2000 PWM has been running for 15 secs. It isalways disabled while in simulator mode to preventfalse alarms or inadvertant operation of the customerlockout.

The Diode Fault alarm sends a one hertz, 0 to 24volt squarewave to the EX2000 PWM. This signalis scaled in the REFVCO. It is then sent to twosignal level detectors. One checks for acontinuously low voltage which indicates a diodefault. The other checks for a continuously highvoltage which indicates a diode monitor fault.

Each of the inputs and resulting signal level detectoutputs are incorporated in the global alarm string30EX and also passed over the status S page.

4-6.2.1. GROUND DETECTOR AND DIODEFAULT SCALING AND CONFIGURATION.The Ground Detector Malfunction input is scaled inthe FBVCO. The feed back VCO scale factorEE.1386 FVSCL0 is set to a value of 10000. Thisscales VAR.183 to a nominal 20000 counts with aninput of 20 V dc. EE.180 SL5LEV is the level thatthe input variable from the FBVCO is compared to.This is set to a value of 18000. The mode of thelevel detect is set to a 0 in EE.178.11 SL5MODE.The level detect will then pick up when the input isgreater than or equal to the sensing level. The leveldetect time delay is set to 0.5 seconds with a settingof 50 in EE.182 SL5PUT.

The Ground Detection input is scaled in theV4VCO. The V4VCO scale factor EE.488 V4SCL0is set to a value of 10609. This scales VAR.185 to anominal 20000 counts with an input of 24 V dc.

This variable is compared to EE.74 in the CMPR1block. EE.74 is a general purpose register and is setto a value of 2000 counts. If the output of V4VCOis greater than 2000 counts, then there is no ground.The delay of 10 seconds is set in the ONDLY3block at EE.5670 ONDLY3. This is set to a valueof 1000 for a 10 second delay.

The Diode Fault input is scaled in the REFVCO.The feed back VCO scale factor EE.1281 RVSCL0is set to a value of 10000. This scales VAR.182 to anominal 20000 counts with an input of 20 V dc.

For a diode monitor fault detection, EE.187SL6LEV is the level that the input variable from theRFVCO is compared to. This is set to a value of18000. The mode of the level detect is set to a 0 inEE.185.11 SL6MODE. The level detect will thenpick up when the input is greater than or equal to thesensing level. The level detect time delay is set to 2seconds with a setting of 200 in EE.189 SL6PUT.

For a diode fault detection, EE.194 SL7LEV is thelevel that the input variable from the REFVCO iscompared to. This is set to a value of 2000. Themode of the level detect is set to a 4 in EE.192.11SL7MODE. The level detect will then pick up when


56

the input is less than the sensing level. The leveldetect time delay is set to 2 seconds with a setting of200 in EE.196 SL7PUT.

4-6.3. Field Thermal Model

The EX2000 PWM monitors the temperature of theexciter field windings by calculating the fieldwinding resistance from the measured values ofexciter field voltage and exciter field current. Insimulator mode, the model uses the simulated valuesof field voltage and current.

From the calculated field resistance, the temperatureof the windings is calculated using the resistanceformula for copper. This temperature is stored inVAR.1011, where it is displayed in degreescentigrade. It can be read directly or sent over theLAN to the operator station.

4-6.3.1. THERMAL MODEL OPERATION.The voltage feedback, VFE (VAR.1014), passesthrough a limiter that restricts it to positive values.This prevents negative values of resistance frombeing calculated. The resulting voltage signal is fedthrough a filter that matches the field voltage to theassociated field current. This is accomplished byproducing a lag that approximates the lagexperienced by the field current due to the field timeconstant. The amount of lag is set using EE.1596EFLTCO.

A switch is used to select either field voltage or avalue of zero. Field voltage is the output if bridgefiring is detected (VAR.882 MPWRENAB is true).This signal becomes the numerator in a dividefunction.

The field current IFE (VAR.1016), after passingthrough a filter, feeds a limiter that only passes fieldcurrent values greater than 500 counts. The signalthen becomes the denominator of the dividefunction. The result of the divide function is thefield resistance in counts. Restricting thedenominator to values above 500 counts eliminatesthe possibility of division by zero.

The resulting resistance count value is normalized toKelvin degrees by multiplying by a scale factor setEE.1594 ERTSFO. The Kelvin degrees are thenconverted back to centigrade by subtracting 235.The temperature, now in degrees centigrade, isfiltered and passed though a limiter that restricts theoutput temperature range to 0 to 300°. Thetemperature is output as VAR.1011 EFG, scaled at 1count equals 1 °C. Due to the time constants, fieldtemperature is not accurately modeled during startupand shutdown of the exciter.

4-6.3.2. THERMAL MODEL SCALING. Theexample system uses VFE and IFE as the feedbackvariables. The model parameters to be set areERTSF0 and EFTLC0.

EE.1594 ERTSCO - Exciter thermal modelresistance to degrees scale factor is set = (32 * MaxV dc link * 5000 * (234.5+t1)) /(AFFLex*20000*(Rf@t1) From the sample data:DC link volts = 360 V dc; AFFLex = 9.54 A dc ;Rf@25C = 4.871 ohms.

EE.1594 =32*360*5000*(234.5+25)/(9.54*20000*4.871) =16082 counts.

The exciter lag field time constant is set byEE.1596. From the sample data, the open circuitexciter field time constant is 0.35 seconds. It will beset to (4096 * 0.458752)/ (T’do exciter).


57

WARNING

CHAPTER 5

STARTUP CHECKS

5-1. INTRODUCTION

This chapter contains basic checks to perform afterinstallation and during initial startup. Consult andstudy all furnished drawings and instructions beforestarting installation. These include outlinedrawings, connection diagrams, and elementarydiagrams. For installation details, refer toapplicable sections of GEH-6011 and GEI-100228Receiving, Storing, and Warranty Instructions.

These checks are not intended as completecommissioning instructions for the EX2000 PWMregulator, but serve as a guide for the sequence oftests and a description of functions and devicesrequiring field tests.

Before application of any power sourceto this equipment, be sure that no toolsor other objects left over fromunpacking or installation are present inthe cabinets, including the bridgeassembly.

5-2. EX2000 PRESTART CHECKS

Each EX2000 PWM is thoroughly tested beforeshipment. This testing process should ensure thatthe regulator will perform properly upon receipt andloading of requisition specific software.

A complete inspection of the EX2000 PWMregulator and associated equipment should beperformed prior to energization of any portion of theregulator controls. Items to look for are shippingdamage to wiring or circuit boards, installationdamage or foreign objects from the

installation process, contamination due to improperstorage, and loosening of connections andcomponents.

Proper grounding and separation of wiring levelsshould also be maintained. Ensure that the groundconnection is sized properly and is connected to asuitable ground point.

5-2.1. Energization And Simulator ControlChecks

The following steps are intended as guide forinstallation and initial startup of the EX2000 PWMregulators. Site specific procedures shouldincorporate these steps to ensure completeness.

1. Verify hardware, proms, and board revisionsusing the ST2000 or Control System Toolboxand job specific software supplied with theequipment. Hardware to check includes theshunt supplied, dynamic discharge resistor,charge control resistor, and options supplied.

If changes to proms or circuit boards arerequired, a Full Calc in ST2000 or ControlSystem Toolbox may be needed. Contact GEMotors & Industrial Systems before changingany values generated by the Full Calc if unsureof the correct settings.

2. Verify jumpers and switch settings as specifiedin ST2000 or Control System Toolbox and therequisition elementary. If changes are made,update the application tool databases to keep anaccurate documentation of the regulator.

3. Perform a complete wire check of all externalconnections to the EX2000 PWM. Inspectionsfor unintentional shorts, induced voltages,correct wiring ampacities, and the like should be


58

made. This will include PT and CT inputs, alarmcontacts, trip contacts, and connections to theoperator’s interface device. Ground detectorconnections and other optional equipment shouldalso be checked.

4. With input disconnects open, check incoming acand dc power for proper levels and polarities.On units with a PMG input, it may not bepractical to check the PMG inputs until initialroll of the equipment. At a minimum, a completewire check of the inputs should be performed.

5. Energize the dc power supply feed to energizeexciter regulator controls. The EX2000 PWMwill go through an initialization process. Duringthis initialization process, hardware and firmwarediagnostic checks are performed. Any faultsgenerated during the initialization should becorrected before proceeding. If an IOS orUC2000 is supplied on the system,communication faults will not be cleared untilthe IOS or UC2000 is operational.

The LDCC display will default to its normal, de-energized state. It should appear similar to thefollowing.

A S 97% I 0 %

The PSCD board has several LED indications ofpower supply levels and test points for checkingthe output of the regulator supplies. Check thesetestpoints for appropriate voltage levels. Refer tothe ST2000 help messages or the individualboard GEI instructions for test points andvoltages.

The DC link voltage should also be checked.Variable VAR.1091 should read thecorresponding voltage in engineering units andshould agree with the level measured. On theIAXS board, connections PL and NL are thepositive and negative link voltages respectively.

6. Turn off the dc supply and repeat the PSCDsupply voltage checks for the ac feed to theEX2000 PWM regulator. The PSCD boardvoltages will be the same as for the dc feed. TheDC link voltage will generally be different thanthe DC link with only the dc supply voltage.

Phase rotation of the ac input is not important inthe EX2000 PWM regulator. But phasing shouldbe checked to ensure accuracy in as builtdrawings. If a single phase ac input is used, itmust be connected to L1 and L3 leads of the acinput device.

If voltage doubling is required, the connectionson CTBA-3 and CTBA-4 should be made. Referto the control elementaries for properconnections.

After independent proper operation with both theac and dc source voltages are observed, bothpower sources should be energized at the sametime. Elimination of either source should haveno noticeable affect on the EX2000 PWMregulator. Only the dc link voltage may beaffected. This check should be performed duringpower checks and on-line operation as well.

7. Using ST2000 or Control System Toolbox,download the appropriate core file to theEX2000 PWM regulator. After the download iscomplete, the regulator will again perform adiagnostic check.

8. In order to thoroughly test the operation of theEX2000 PWM regulator, operation in thesimulator mode is recommended. Place thecontrol core in the simulator mode (EE.570.0=1).See Chapter 6 for operation and scalinginformation of the simulator. It is alsorecommended that as much testing be performedin simulator mode as possible. This should helpshorten the pre-startup and initial roll checksgreatly since control functions, alarms, trips, etc.will have been tested and verified correct.

NOTE

In the simulator mode, the EX2000 cangenerate a request for lockout. This cantrip the lockout relay unless thefunction is disabled.


59

9. It may be necessary to place temporary jumperson inputs to simulate breaker closures or startpermissives that may not be operable at this time.One such input is to reset the lockout relay (86)or place a temporary jumper to simulate lockoutrelay. Refer to hardware elementaries forspecific jumpers required. If temporary jumpersare used, it is important to remember to check theoperation of these inputs from the actual devicesat some point during the pre-start process.

10.If the operator’s station device is available, astart from this device may be given and properoperation of the controls should be tested andobserved. Raise and lower signals, alarms,limits, displays and transducer outputs areavailable in the simulator mode.

11.Close or jumper circuit breaker auxiliary contact(52G) input to simulate on-line operation.

Change EE.84 value to simulate higher turbineload. UEL settings can be checked by increasingEE.84 lowering the regulator output, andcomparing to the capability curve.

NOTE

Return EE.84 value to(152*frequency/60) before opening the52G contact or the simulator willoverspeed and cause a trip.

12. Verification of the operation of the on-line andoff-line OEL Limiters can be accomplished throughthe use of the built in simulator and ST2000. Aconvenient way to do this is to utilize the two inputsummation (2 Input Sum) block that is programmedbetween the REF2 block output and the COREblock EFR@SP input. EFR@SP is the setpoint forthe field regulator. The summation block was addedto the pattern for test purposes only. Input 1 of thisblock is the normal field regulator referencesupplied by REF2 output. Input 2 can be pointed tothe output of the background test oscillator. In thismanner the regulator can be easily stepped.

a. Off-line OELWhile in manual regulator, raise theexcitation level until the field current exceedsthe off-line OEL pickup level. The systemgoes into off-line OEL. Lower the referenceto see that the OEL condition resets. Step thereference into OEL and observe the response.Return the summation block test input to zero.

b. On-line OELWhile in manual regulator and with about90% MW load, increase the VARs until fieldcurrent is above 112% of AFFL. The PRIT1block begins to accumulate and after a timedelay activates the OEL limiter. Lower thesetpoint and then step the reference so that thesystem goes back into on-line OEL. Observethe response and be aware that if a very largestep is used, the signal level detector pickuplevel is also exceeded. After 10 seconds, theexciter field current will be limited to 125%of AFFLex and when PRIT1 times out it willlimit to 100% of AFFLex.

After completion of the tests, be sure to disconnectthe test oscillator.

5-3. PRE-START POWER CHECKS

1. After proper simulator operation, remove thecontrol core from simulator mode. As describedin section 4-4.4 Feedback Offsets, the inputsfrom the current and voltage feedbacks should beadjusted.. These offsets are found in locationEE.1508 through EE.1513. In simulator mode,these values are not in use and therefore do notaffect the simulator operation.

2. Check PT and CT inputs by applying an inputsignal with a 3-phase source at rated PTsecondary volts and CT secondary current. Theoperator station device should display ratedterminal volts. Internal control variables for PTand CT feedbacks should be verified for properscaling. If supplied, a PT failure can be checkedby opening the primary switch and observing atransfer to the backup PTs or a transfer to themanual regulator.


60

3. It is recommended that the brushless exciter fieldbe used for initial power tests. There should beno detrimental effects to using the exciter field asa load since the unit is not rotating and can notproduce generator field voltage. If the exciterfield is not available, a suitable replacement loadmust be used. This dummy load has to beinductive. If a simple resistive load is used thecontrol will trip on instanteous over currentbefore the regulator can limit the current. Sincethe EX2000 PWM regulator is a currentregulator, it should be sized to carry at leastAFFLex in order to keep as many EE settings atthe requisition levels as possible. Choosing asmaller current load will require adjustment ofseveral operating parameters.

4. Place the controls in manual regulator. Connectan oscilloscope and voltmeter to the output loadleads. Incorrect shunt wiring can cause theEX2000 PWM regulator to turn full on in manualmode. Verify shunt connections with a millivoltsource, observing proper polarities, beforestarting.

Again, test jumpers or operation of the 86Gdevice will be required to run the EX2000 PWMregulator into the exciter field or replacementload.

5. Upon starting the regulator, exciter field currentshould develop to approximately 80% AFNL.Immediately stop the controls if any unusual orabnormal operation occurs. Operation in theautomatic regulator is not recommended sincethe regulator will be open loop and be verydifficult to control.

6. Measure field voltage and current and compareto the operator station display values. UseST2000 or Control System Toolbox to check theVCO output counts for proper values. While thescaling can be adjusted to give the desired countsfor the indicated voltages or currents, it isgenerally an indication of improper scaling orjumper settings when these values are not inagreement.

7. Check field output waveshapes using anoscilloscope. Observe for stable operation at lowand full output voltages. The display should be asquare wave similar to Figure 5-1. As output israised, the on-time will increase as the off-timewill decrease. The upper and lower peaks of thesquare wave will be equal to the dc link voltage.

DC LINK LEVEL

O VOLTS LEVEL

LOW OUTPUT HIGH OUTPUT

Figure 5-1. Typical Output Wave Forms


61

8. Use the method outlined in the OEL simulatortesting section 5-2, step 12 to verify off-line andon-line OEL limit and regulator stability. Ajumper for the 52G input will be required tosimulate on-line operation. It will not benecessary to simulate MW’s on the EX2000PWM regulator. Raising the output current tothe OEL settings should result in OEL limiteroperation as described. For checks without theactual exciter field, it is possible to simulatehigher current levels by changing the value inEE.1505. This value should be restored to theoriginal setting after testing. If found to beunstable, contact GE Motors & IndustrialSystems for any changes in settings.

9. Restore values and reconnect for normaloperation. Check temporary inputs, jumpers andEE values and restore to the desired operationalsettings. The unit is now ready for off-line,initial roll system checks.

5-4. INITIAL ROLL OFF-LINE CHECKS

1. Run the unit up to synchronous speed. At thistime the PMG input may be available for the firsttime. Before applying the PMG input, measureand observe correct PMG inputs. Refer toapplicable PMG instruction manuals for moreinformation.

2. With the EX2000 PWM regulator in manualcontrol, start the exciter. The unit should comeup to approximately 80% amps field no load.This should result in a build up of generatorterminal voltage no greater than rated terminalvolts when operating at rated generatorfrequency.

3. Refer to applicable instruction manuals for initialstartup checks for the rotating portions of thebrushless exciter and main generator. Thisshould include ground detector operationalchecks as well.

4. Check phasing of the PT inputs. CT inputs willnot be available at this time. Measure for correctsecondary values at rated generator terminalvolts. Negative generator frequency counts areindicative of improper phase rotation of the PTinputs.

Check for the values of exciter field volts andexciter field current at no load used to scale theexciter. Measure the actual field volts and fieldshunt millivolts. The measured values, countsand operator station display values should be inagreement.

5. Step tests of the exciter field regulator should beperformed to ensure stable operation. Step testthe field voltage regulator using the inputsumming block as described in the OELsimulator testing.

6. Transfer to automatic regulator. The transfershould be smooth and without any noticeablefluctuations in generator or regulator operation.The AVR can be stepped by pointing the extrareference in the Excitation Autosetpoint Block(EE.3781 ASP@EX) to the output of the testoscillator. Generally a 2% step (400 counts) issufficient. Verify stability of the AVR.

7. Give the regulator a stop command. With theunit in automatic regulator, restart the exciter andwatch for proper operation. The EX2000 shouldbring the generator to rated terminal volts (or thesetting of the EE.3402 pointer).

8. The V/HZ regulator function can be checked byslowing the generator and, while in automaticregulator, watching the ac terminal volts dropaccordingly. A 1.10 pu ratio should not beexceeded.

The EX2000 PWM regulator is now ready for on-line operation. Return the unit to rated terminalvolts. Initial synchronization checks for otherequipment may be required at this time.


62

WARNING

5-5. ON-LINE CHECKS

1. It is recommended that the unit be synchronizedin manual regulator the first time. The CT inputsto the EX2000 PWM regulator can adverselyaffect the automatic regulator operation if theyare not correct. Once the unit has beensynchronized, increase the unit load for a smallamount of generator line current.

Check the MW and MVAR displays for positivevalues. If they are negative, the CT leadsconnections may be reversed. This conditionshould be corrected before proceeding. If thereare no CT disconnects, the unit must be off-lineto reverse/change CT connections.

Reversing CT leads with the unit underload can cause substantial damage togenerator components. The unit mustbe off-line, 52G open, before correctingCT lead polarity.

2. After correct displays of MW and MVars hasbeen ascertained, place the regulator inautomatic. For units without PT failuredetection, remove the main PT input by openingthe disconnect switch (if supplied) or pulling thePTCT board input connection plug. Thisgenerates a PT undervoltage alarm. The operatorstation display should indicate that the regulatorhas transferred to manual, and can not be placedinto automatic. A 30EX global alarm should begenerated. Restoring the PT input and operatingthe PT BAD reset will allow a return toautomatic. Activating the automatic regulatorselection should again place the exciter inautomatic regulator. The 30EX alarm should beclear.

Two PT inputs are required for PT failuredetection. Opening the main PT will generate aPT failure alarm but the unit will not transfer tomanual. It will continue regulation on thesecondary set of PTs. Restoring the main PTinput will clear the PT bad alarm.

Removing only the secondary PT input willgenerate a PTX alarm but will not transfer theunit from automatic to manual. Restoring the PTinput will clear the alarm.

Removing both the primary and backup PTinputs will generate the PT undervoltage alarmand the restoration process described aboveshould be followed.

3. Check UEL operation. The simulator checksshould be sufficient to guarantee properoperation of the UEL at the desired setpoints aslong as the line current and line voltage countvalues are correct. Many customers may requireverification of the actual UEL limit line. If thisis needed, the UEL stability should be checkedfirst.

Stability of the UEL can be checked by raisingthe UEL setpoints to a value of just slightlyunderexcited. The values of EE.2872, EE.2865,EE.2867, and EE.2869 should be set to negative250 counts. Lower the excitation slowly untilthe UEL regulator takes over at the revisedsettings. The EX2000 PWM regulator can thenbe stepped into the UEL regulator using the extrainput to the auto setpoint block as described insection 5-4, step 8. This will verify that the UELoperation is stable. Contact GE Motors &Industrial Systems if any instability in the UELregulator is encountered.

If at any time undesired operation is observed, atransfer to manual regulator should correct thecondition. After verification of UEL stability,the original UEL setpoints should be restored. Ifthe customer desires testing of the actual UELlimits, the excitation can be slowly lowered intothe limit.

4. The on-line OEL testing performed in section 5-3, step 7 should be sufficient. To perform thesame test on the actual machine requiresoperation at very high field current levels. GEMotors & Industrial Systems does notrecommend that the equipment be actually driveninto OEL. If it is required, contact GE Motors &Industrial Systems.


63

After completion of all EX2000 tests, restore allstorage registers used for testing to normalvalues, back up the software, and disable allwrite enables.

As the unit is loaded, check for reactive sharingbetween paralleled units. Reactive currentcompensation can be introduced through the AVRsetpoint block by changing the gain of the RCC.See EE.3791 help for changing the RCC gain.

5-6. OPERATOR INTERFACE

The EX2000 PWM regulator is a versatile regulator,capable of communicating with several differentHuman-Machine Interfaces. Direct communicationwith the GE turbine control is the standard, primaryoperator’s station and interface to the EX2000PWM. The communication configuration is definedand standardized within both the turbine controllerand the EX2000 PWM. Changes to the Status Spage and communication settings should be madeonly under advisement from GE Motors andIndustrial Systems.

Check out of the Status S communications should becarried out in conjunction with the turbine controlstartup procedures. Usually it is sufficient to verifycontrol of operator functions as described on theinterface control panel or screen.

5-6.1. Units With UC2000 or IOS

All UC2000s and IOSs are factory-tested andoperable when shipped to the installation site. Finalchecks should be made after installation and beforestarting the UC2000/OC2000 combination or theIOS. Consult the appropriate equipment GEH forguidelines for inspections to perform prior tostartup.

GEH-6335 Operator Console 2000 Operation and Maintenance

GEH-6334 Unit Controller 2000 Operation and Maintenance

GEH-6122 Intelligent Operators Station Operation and Maintenance

5-6.2. Units With Discrete Switches AndMeters

Testing of contact inputs and outputs from discretemeters and switches should include a thoroughwiring check for continuity and no direct shortsbefore powering the devices from the EX2000PWM. Normal startup checkouts will ensure correctconnections and operation of the devices.


64

Notes:


65

CAUTION

CHAPTER 6

SIMULATOR SCALING AND OPERATION

6-1. EX2000 PWM SIMULATOR

A simulator is built into the EX2000 PWM that canmodel a generator and brushless excitation systemoff-line or on-line (connected to an infinite bus).Simulator operation is selected by settingEE.570.0 = 1. When selected, the feedbackspresented to the control regulators are switched, bysoftware, from the real feedback inputs to feedbacksderived by mathematical models mimicking thegenerator and field circuit behavior.

The EX2000 PWM controls react in a manner closeto the way they would react in normal operation.The simulator can serve as a valuable startup,maintenance, and training tool.

The simulator is scaled to represent the actualsystem as accurately as possible. This means thatwhen a start command is given to the EX2000, itfollows a normal start sequence. Close commandsare sent to the bridge contactor but gating of theIGBT devices is disabled. The controls look foractual auxiliary contact feedbacks representing thecontactor states. If these are not correct theappropriate faults are generated.

The generator armature and field models, as well asthe exciter stator and field models, provide thefeedbacks for exciter field voltage and current andgenerator stator voltage and current. Thesefeedbacks are handled by the transduceringalgorithms the same way real feedbacks are used tocalculate watts, VARs, speed deviation, andfrequency. If the model scaling is correct, thedisplay data cannot be distinguished from real data.Main generator field voltages and currents are alsosimulated internally and used for correct modeloperation.

The exciter regulator can be raised and lowered inautomatic or manual regulator, both on-line or off-line. The regulator limits come in at the same levelsas in non-simulated operation. The regulatorresponses provide a good representation of what canbe expected of the real system in response to stepchanges.

By changing the storage register containing thevalue representing model shaft torque, EE.84, it ispossible to raise or lower the generator real poweroutput when simulating on-line operation. Theexciter changes the system VARs in response tochanges in the exciter setpoints.

Disable the IGBT gating while insimulator mode. Check that setting ofEE.589.14 = 0.

6-1.1. Simulator Scaling

The goal of the simulator scaling is to make themodels represent, as close as possible, the behaviorof the real system.

In addition to the following EE settings, seeEE.3850 GMJMPR in section 4-3. Generator,exciter, and regulator parameters listed in section 4-2 for the example system will be used for scalingdiscussions in the simulator section.

SMVDCL0 EE.1558 simulates the dc link voltageof the EX2000 PWM regulator. It is set to representthe actual running voltage of the dc link. For theexample system this is 137 V dc. For EE.1558, setequal to 137/360 * 20000 = 7611 counts.


66

SMHST0 EE.1559 is the simulated heat sinktemperature of the PWM IGBT heatsink. This valuecan be used to test the overtemperature alarm andtrip levels in the regulator controls. One countequals 1 °C. Normally set to maximum expectedtemperature during operation, 60 °C.

GMVBAT EE.3851 represents simulator flashingvoltage. Since flashing is not required on theEX2000 PWM regulators, set EE.3851 = 0.

GMRBAT EE.3852 represents simulator batteryresistance for field flashing. This is also notrequired in the EX2000 PWM and EE.3852 is alsoset to a 0.

GMVTHY EE.3853 is the simulator thyrite voltage.This models an overvoltage protection thyriteconnected across the exciter field input. Theexample system has a 125 V exciter field.Set EE.3853 = (Exciter field class*7.2*1797)/(DClink volts) = (125*7.2*1797)/137 = 11805.

GMRDIS EE.3854 simulates the dynamic dischargeresistance. Set EE.3854 =(AFNLex*2*RDD*30664) / DC link volts =(3.52*2*17*30664)/137 = 26787.

GM_RFE EE.3855 is the simulator exciter fieldresistance. This is set equal to (VFNLex/DC linkvolts) * 31108 where VFNLex = AFNLex *Rfe@25C. From the example data Rfe@25c =4.871 ohms. VFNLex = 4.871 * 3.52 = 17.15 V dc.Set EE.3855 = (17.15/137)*31108 = 3838.

GMILFE EE.3856 represents the inverse of exciterfield inductance. EE.3856 is set equal to (DC linkvolts * 156) / (VFNLex * T’doex). T'doex is theopen circuit field time constant which is 0.35seconds in the example system. Set EE.3856 =(137*156) / (17.15 * 0.35) = 3561.

GM_RFG EE.3857 simulates generator fieldresistance. This parameter is normally set to 7115 *frequency/60. The constant scaling is the result ofexpected normalizations. Exciter AFNL is expectedto produce VFNL on the generator field which inturn produces AFNL on the generator field. SetEE.3857 = 7115 for the example, which is a 60 Hzsystem.

GMILFG EE.3858 is the simulated inverse ofgenerator field inductance. Set equal to (60/frequency) * 670 / T'dogen, where T'do is the maingenerator field time constant. Set EE.3858 =670/5.615 = 119 for the example system.

GMVFES EE.3859 is the simulator exciter voltagescale down divider. This scales the exciter voltagefrom the model to produce EXSIMFE VAR.1177(simulated exciter field voltage). Set EE.3859 =5888 * maximum dc link volts / dc link volts = 5888* 360/137 = 15472.

GMIFES EE.3860 is the simulator exciter currentscale down divider. This parameter scales theexciter current from the model to make EXSIMIFEVAR.1176 (simulated exciter field current). SetEE.3860 = (AFFLex/AFNLex)*3146 =(3.52/9.54)*3146 = 8526.

GMVFGS EE.3861 is the simulator generator fieldvoltage scale down divider. This parameter scalesgenerator field voltage from the model to makeEXSIMVFG VAR.1163. Set GMVFGS to27329280/ (AFNLgen * RFG@100 C* 20000 /Maximum DC link volts). In the example system,and simplifying the formula, this is 1367 * 360 /(313*0.256) = 6139.

GMIFGS EE.3862 is the simulator generator fieldcurrent scale down divider. This parameter scalesgenerator field current from the model to makeEXSIMIFG VAR.1161 (simulated generator fieldcurrent). When used in conjunction with standardscaling, such as AFFL = 5000 counts, set GMIFGS= (AFFLgen / AFNLgen ) * 3146. In the examplesystem, this would be 846/313*3146 = 8503.

GMIFLS EE.3863 represents the simulator flashingcurrent scale down divider. This parameter is notused in the EX2000 PWM regulator. SetGMVIFLS = 0.

GMDAMP EE.3864 is the simulator generatormodel damping factor where 1 count = 0.11 puwatts/pu speed(60 Hz). Normally EE.3864 is setequal to 400. If oscillations occur while operatingin simulator mode, try changing GMDAMP.


67

GM_IXS EE.3865 represents the generator modelinverse of synchronous reactance. This parametermodels the generator synchronous reactance insimulator mode. GM_IXS = 4096/Xs(pu).

To most accurately model the generator, it isnecessary to approximate the generator synchronousreactance from no load to full load. In a real system,machine reactances vary with saturation andsaliency. Therefore it is necessary to makesimplifying assumptions that produce a value of Xsthat provides reasonable behavior over the rangeVFNL to VFFL. Assume a round rotor machinewith no saturation, no saliency, and resistance isnegligible. This makes the direct and quadraturereactances equal. If this level of accuracy in themodel is not of concern then Xd (the direct axissaturated synchronous reactance) can be used.

If optimum model accuracy is of concern then thefollowing method, based on a simplifiedsynchronous machine model, can be used. Therange of field amps from no load to full load =AFFL/AFNL=9.54/3.52 = 2.71.

If a phasor diagram showing the machine operatingat rated load and power factor connected to aninfinite bus at rated terminal volts is drawn then aquadratic equation with the synchronous impedanceas the unknown quantity can be generated andsolved for Xs. It is then used in the above equationfor GM_IXS.

The rated power factor for the sample machine is0.85. With the machine operating at rated k VA = 1pu k VA then rated real power = 0.85*1 pu andrated reactive power output = 0.53*1 pu Generatorvoltage = 1 pu

As per unit values are being used it is not necessaryto use the actual generator MW and MVAR valuesinvolved.

From the phasor diagram, the following quadraticequation results where the generator internal voltagerange required is represented by the ratio of AFFLto AFNL = 2.71

(2.71)**2 = (1 + 0.53*Xs)**2 + (0.85*Xs)**2Solving for Xs gives a synchronous reactance of2.04 pu

Set EE.3865 equal to 4096/Xs = 4096/2.04 = 2007.

GMXEXS EE.3866 models the effect of externalreactance for the simulator generator model. Thiscan be set for a strongly or weakly connectedsystem. EE.3866 is set equal to 65536*Xe/(Xs +Xe) where Xe represents the amount of impedancein per unit connecting the generator to the system.For the example, set for a strong system (smallamount of impedance between generator andsystem), with Xe = 0.1 pu, then EE.3866 =65536*(0.1)/(2.04 + 0.1) = 3062.

GM_IM EE.3867 models the effect of generatorinertia for the simulator. Typically, the defaultvalue of zero (which is equivalent to M = 3.98 pu) isused. For more accurate simulator modeling,EE.3867 can be set to (frequency/60)*16302/Mwhere M =2H, the generator inertia constant.

6-1.2. Operation

To put the control core into simulator mode setEE.570.0 = 1. The shaft speed of the generatorincreases to rated (synchronous) speed at a ratedetermined by the simulator inertia constant and thelevel of shaft torque preset in register EE.84. Thevalue of torque preset to give rated speed at no loadis 153 * (frequency/60). Rated speed is indicated onthe core programmer display as 100%. The shafttorque can be altered on-line or off-line by changingthe value stored in EE.84. Off-line, changing shafttorque increases the speed and hence the frequencyof the generator. Changing the torque on-lineincreases or decreases the real power output of themodel generator.

To start the simulator, it is generally necessary towait until the simulated generator speed is above95%. It is also necessary to have the 86G input tothe EX2000 PWM regulator closed. Failure to do so


66

CAUTION

will result in a fault 29 when attempting a start.Starts in auto or manual regulator are permissible.The simulator can be started from the operatorsstation or by pressing the RUN button on the LDCCkeypad. After starting, exciter field current andvoltage and generator terminal voltage will build upto the preset levels of the regulator being used.

Once the simulator is on-line, the 94EXcontact output can be operatedinadvertently. This may causeunintentional operation of protectivedevices outside the EX2000 PWMregulator. Lifting of the 94EX outputcontacts is recommended duringsimulator operation.

To put the simulator on-line, a contact closuresimulating 52G aux contact feedback must be inputto core LTB input IN1. Some oscillations aregenerally observed when closing the 52G contactsince there is no synchroscope to confirm closingwhile the simulated generator and line voltages arein phase. When off-line, changing the exciter AVRor MVR setting adjusts generator terminal voltage.When on-line, raise or lower signals change thegenerator VARs. The result of these controlchanges can be observed.

Testing of UEL settings, V/hz regulator, overcurrent protections, and so on, can also be observed.Feedback and control signals from the operatorsstation and 4-20 ma outputs (if supplied) can also beobserved.

When stopping the simulator, the reference value inEE.84 should be returned to the original level for100% speed off-line. Failure to do so will result inunusual off-line operation.

Reader CommentsGeneral Electric Company

We welcome comments and suggestions to make this publication more useful.

Name Telephone Number

Company Name Fax Number

Address Job Site

GE Requisition Number

Publication No. Issue/Revision Date Today’s Date

GENERAL COMMENTS

Excellent Good Fair PoorContents � � � �

Organization � � � �

Technical accuracy � � � �

Clarity � � � �

Completeness � � � �

Drawings, figures, and tables � � � �

Referencing and tables of contents � � � �

Readability � � � �

SPECIFIC COMMENTS (Corrections, information that could be expanded, and so on)

Page Number Comment

Other suggestions for improving this publication:

As compared to publications from other manufacturers of similar products, how would you rate this document?

� Superior � Comparable � Inferior � Do not know

Indicate the type of user/reader function that best describes you:

� System Integrator � Distributor � OEM � Installation� Programmer � Maintenance � Operator � Other (please specify) ______________________

Detach, fold, and mail.

To:GE Motors & Industrial SystemsTechnical Publications, Room 1911501 Roanoke Blvd.Salem, VA 24153–6492 USA

.................................................................................................... Fold here and close with staple or tape ....................................................................................................

Placestamphere

GE Motors & Industrial SystemsTechnical Publications, Room 1911501 Roanoke Blvd.Salem, VA 24153–6492 USA

..........................................................................................................................Fold here first..........................................................................................................................Electric Company

Issue Date: April 1997© 1997 by General Electric Company, USA.All rights reserved.

Documents

Digital Exciter