AC DRIVESTechnical guide book.pdf

8/9/2019 AC DRIVESTechnical guide book.pdf

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AC Drives Technical Guide Book


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3/316AC Drives Technical Guide B ook

This is the first AC Drives Technical Guide Book, a completeset of ABB's Technical Guides 1-8.

We wish that the accumulated knowledge of world'sleading AC Drives manufacturer will work for your benefit.The aim of this book is to provide you a solid tool for everyday use in the arena of AC drives.

Best regards,

Mika Kulju

Product Management

We updated existing Guides over time, so the latestversions and new Technical Guides can be found from ourweb site: http://www.abb.com/motors&drives

Dear Reader,


4/316AC Drives Technical Guide Boo k


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Contents

1. Direct Torque Control explains what DTC is; whyand how it has evolved; the basic theory behind itssuccess; and the features and benefits of this new

technology.

2. EU Council Directives and Adjustable SpeedElectrical Power Drive Systems is to give astraightforward explanation of how the various EUCouncil Directives relate to Power Drive Systems.

3. EMC Compliant Installation and Configuration fora Power Drive System assists design and installationpersonnel when trying to ensure compliance with therequirements of the EMC Directive in the user'ssystems and installations when using AC Drives.

4. Guide to Variable Speed Drives describes basics ofdifferent variable speed drives (VSD) and how they areused in industrial processes.

5. Bearing Currents in Modern AC Drive Systemsexplains how to avoid damages.

6. Guide to Harmonics with AC Drives describesharmonic distortion, its sources and effect, and alsodistortion calculation and evaluation with specialattention to the methods for reducing harmonics withAC drives.

7. Dimensioning of a Drives system. Makingdimensioning correctly is the fastest way of savingmoney. Biggest savings can be achieved by avoidingvery basic mistakes. These dimensioning basics and

beyond can be found in this guide.

8. Electrical Braking describes the practical solutionsavailable in reducing stored energy and t ransferringstored energy back into electrical energy.

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Direct Torque Control- the world's most advanced AC drive technology

Technical Guide No. 1Technical Guide No. 1


8/316Technical Guide No.1- Direct Torque Cont rol 2


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Contents

1 Introduction ......................................................General ......................................................................This Manual’s Purpose .............................................Using this Guide ........................................................

2 Evolution of Direct Torque Control ...................What is a Variable Speed Drive? ..............................Summary ...................................................................DC Motor Drives .......................................................

Features .................................................................

Advantages ...........................................................Drawbacks ............................................................AC Drives - Introduct ion ...........................................AC Drives - Frequency Control using PWM ............

Features .................................................................Advantages .........................................................Drawbacks ..........................................................

AC Drives - Flux Vector Control using PWM .........Features ...............................................................Advantages .........................................................Drawbacks ..........................................................

AC Drives - Direct Torque Control .........................Controlling Variables ...........................................

Comparison of Variable Speed Drives ...................

3 Questions and Answers ..................................General ....................................................................Performance............................................................Operation .................................................................

4 Basic Control Theory ......................................How DTC Works ......................................................

Torque Control Loop ...............................................Step 1 Voltage and Current Measurements ......Step 2 Adaptive Motor Model ............................Step 3 Torque Comparator and Flux ComparatorStep 4 Optimum Pulse Selector .........................

Speed Control .........................................................Step 5 Torque Reference Controller ..................Step 6 Speed Controller .....................................Step 7 Flux Reference Controller .......................

5 Index ...............................................................

5555

66677

78899

101010101111

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15151622

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272727282829292929

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Technical Guide No.1- Direct Torque Co ntrol

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Direct Torque Control - or DTC - is the most advanced ACdrive technology developed by any manufacturer in the world.

The purpose of this Technical Guide is to explain what DTCis; why and how it has evolved; the basic theory behind itssuccess; and the features and benefits of this new technology.

While trying to be as practical as possible, this guide doesrequire a basic understanding of AC motor control principles.

It is aimed at decision makers including designers, specifiers,purchasing managers, OEMs and end-users; in all marketssuch as the water, chemical, pulp and paper, powergeneration, material handling, air conditioning and otherindustries.

In fact , anyone using variable speed drives (VSD) and whowould like to benefit from VSD technology will find thisTechnical Guide essential reading.

This guide has been designed to give a logical build up as to

why and how DTC was developed.

Readers wanting to know the evolution of drives from earlyDC techniques through AC to DTC should start at Chapter 2(page 6).

For those readers wanting answers about DTC’s performance,operation and application potential, please go straight toChapter 3 (page 15) Questions & Answers.

For an understanding of DTC’s Basic Control Theory, turn to

page 26.

Chapter 1 - Introduct ion

This manual’s purpose

General

Using this

guide


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Summary

What is a variable speed drive?

Chapter 2 - Evolution of Direct Torque Contro l

To understand the answer to this question we have tounderstand that the basic function of a variable speed drive(VSD) is to control the flow of energy from the mains to theprocess.

Energy is supplied to the process through the motor shaft.Two physical quantities describe the state of the shaft:torque and speed. To control the flow of energy we musttherefore, ultimately, control these quantities.

In practice, either one of them is controlled and we speakof “torque control” or “speed control”. When the VSDoperates in torque control mode, the speed is determinedby the load. Likewise, when operated in speed control, thetorque is determined by the load.

Initially, DC motors were used as VSDs because they couldeasily achieve the required speed and torque without theneed for sophisticated electronics.

However, the evolution of AC variable speed drive technology

has been driven partly by the desire to emulate theexcellent performance of the DC motor, such as fast torqueresponse and speed accuracy, while using rugged,inexpensive and maintenance free AC motors.

In th is sec t ion w e look a t the evo lu t ion o f

DTC, char t ing the fou r m i les tones o f

var iab le speed dr ives , name ly :

• DC Motor Drives 7

• AC Drives, frequency control, PWM 9• AC Drives, flux vector cont rol, PWM 10• AC Drives, Direct Torque Control 12

We examine each in turn, leading to a total picture thatidentifies the key differences between each.

Technical Guide No.1- Direct Torque Cont rol 6


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DC Motor Drives

• Field orientation via mechanical commutator• Controlling variables are Armature Current

and Field Current, measured DIRECTLY from the motor• Torque control is direct

In a DC motor, the magnetic f ield is created by the currentthrough the field winding in the stator. This field is always atright angles to the field created by the armature winding.This condition, known as field orientation, is needed togenerate maximum torque. The commutator-brushassembly ensures this condition is maintained regardlessof the rotor position.

Once field orientation is achieved, the DC motor’s torque iseasily controlled by varying the armature current and bykeeping the magnetising current constant.

The advantage of DC drives is that speed and torque - thetwo main concerns of the end-user - are controlled directlythrough armature current: that is the torque is the innercontrol loop and the speed is the outer control loop (seeFigure 1).

Accurate and fast torque control• High dynamic speed response• Simple to control

Initially, DC drives were used for variable speed controlbecause they could easily achieve a good torque and speedresponse with high accuracy.

Figure 1: Contro l loop of a DC Mo tor Drive

Evolution of Direct Torq ue Contro l

Features

Advantages


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CustomerLocation

ApplicationEquipment Supplied

A DC machine is able to produce a torque that is:

• Direct - the motor torque is proportional to the armature

current: the torque can thus be controlled directly andaccurately.• Rapid - torque control is fast; the drive system can have

a very high dynamic speed response. Torque can bechanged instantaneously if the motor is fed from an idealcurrent source. A voltage fed drive still has a fastresponse, since this is determined only by the rotor’selectrical time constant (i.e. the total inductance andresistance in the armature circuit)

• Simple - field orientation is achieved using a simplemechanical device called a commutator/brush assembly.

Hence, there is no need for complex electronic controlcircuitry, which would increase the cost of the motorcontroller.

• Reduced motor reliability• Regular maintenance• Motor costly to purchase• Needs encoder for feedback

The main drawback of this technique is the reduced reliabilityof the DC motor; the fact that brushes and commutators

wear down and need regular servicing; that DC motorscan be costly to purchase; and that they require encodersfor speed and position feedback.

While a DC drive produces an easily controlled torque fromzero to base speed and beyond, the motor’s mechanicsare more complex and require regular maintenance.

• Small size• Robust• Simple in design

• Light and compact• Low maintenance• Low cost

The evolution of AC variable speed drive technology has beenpartly driven by the desire to emulate the performance ofthe DC drive, such as fast torque response and speedaccuracy, while utilising the advantages offered by thestandard AC motor.

Drawbacks

AC Drives - Introduction

Evolution of Direct Torqu e Control



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• Controlling variables are Voltage and Frequency

• Simulation of variable AC sine wave using modulator• Flux provided with constant V/f ratio• Open-loop drive• Load dictates torque level

Unlike a DC drive, the AC drive frequency control techniqueuses parameters generated outside of the motor as controllingvariables, namely voltage and frequency.

Both voltage and frequency reference are fed into a modulatorwhich simulates an AC sine wave and feeds this to the motor’s

stator windings. This technique is called Pulse WidthModulation (PWM) and utilises the fact that there is a dioderectifier towards the mains and the intermediate DC voltageis kept constant. The inverter controls the motor in the formof a PWM pulse train dictating both the voltage and frequency.

Significantly, this method does not use a feedback devicewhich takes speed or position measurements from themotor’s shaft and feeds these back into the control loop.

Such an arrangement, without a feedback device, is called

an “open-loop drive”.

Figure 2: Contro l loop of an AC Drive with frequenc y control using PWM


Features

AC Drives - frequency control using PWM


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• Low cost• No feedback device required - simple

Because there is no feedback device, the controlling principleoffers a low cost and simple solution to controlling economicalAC induction motors.

This type of drive is suitable for applications which do notrequire high levels of accuracy or precision, such as pumpsand fans.

• Field orientation not used• Motor status ignored• Torque is not controlled

• Delaying modulator used

With this technique, sometimes known as Scalar Control,field orientation of the motor is not used. Instead, frequencyand voltage are the main control variables and are applied tothe stator windings. The status of the rotor is ignored,meaning that no speed or position signal is fed back.

Therefore, torque cannot be controlled with any degree ofaccuracy. Furthermore, the technique uses a modulator whichbasically slows down communication between the incoming

voltage and frequency signals and the need for the motor torespond to this changing signal.

Advantages

AC Drives - flux vecto r control using PWM

Evolution of Direct Torque Contro l

Features

Drawbacks

Figure 3: Contro l loop of an AC D rive with flux vector c ontro l using PWM

• Field-oriented control - simulates DC drive• Motor electrical characteristics are simulated

- “Motor Model”

• Closed-loop drive• Torque controlled INDIRECTLY



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To emulate the magnetic operating condit ions of a DC motor,i.e. to perform the field orientation process, the flux-vectordrive needs to know the spatial angular position of the

rotor flux inside the AC induction motor.

With flux vector PWM drives, field orientation is achieved byelectronic means rather than the mechanical commutator/ brush assembly of the DC motor.

Firstly, information about the rotor status is obtained by feedingback rotor speed and angular position relative to the statorfield by means of a pulse encoder. A drive that uses speedencoders is referred to as a “closed-loop drive”.

Also the motor’s electrical characteristics are mathematicallymodelled with microprocessors used to process the data.

The electronic controller of a flux-vector drive creates electricalquantities such as voltage, current and frequency, which arethe controlling variables, and feeds these through a modulatorto the AC induct ion motor. Torque, therefore, is controlledINDIRECTLY.

• Good torque response• Accurate speed control

• Full torque at zero speed• Performance approaching DC drive

Flux vector control achieves full torque at zero speed, givingit a performance very close to that of a DC drive.

• Feedback is needed• Cost ly• Modulator needed

To achieve a high level of torque response and speed accuracy,

a feedback device is required. This can be costly and alsoadds complexity to the traditional simple AC induction motor.

Also, a modulator is used, which slows down communicationbetween the incoming voltage and frequency signals andthe need for the motor to respond to this changing signal.

Although the motor is mechanically simple, the drive iselectrically complex.


Advantages

Drawbacks


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With the revolutionary DTC technology developed by ABB,field orientation is achieved without feedback using advancedmotor theory to calculate the motor torque directly andwithout using modulation. The controlling variables aremotor magnetising flux and motor torque.

With DTC there is no modulator and no requirement for atachometer or posit ion encoder to feed back the speed orposition of the motor shaft.

DTC uses the fastest digital signal processing hardware

available and a more advanced mathematical understandingof how a motor works.

The result is a drive with a torque response that is typically10 times faster than any AC or DC drive. The dynamic speedaccuracy of DTC drives will be 8 times better than anyopen loop AC drives and comparable to a DC drive that isusing feedback.

DTC produces the first “universal” drive with the capabilityto perform like either an AC or DC drive.

The remaining sections in this guide highlight the featuresand advantages of DTC.

AC Drives - Direct Torq ue Control

Figure 4: Control loop of an AC Drive using DTC


Controll ing Variables



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Compar ison of variable speed d rives


Figure 1: Contro l loop of a DC Drive

Figure 3: Contro l loop with flux vector control

Figure 2: Contro l loop with frequency control

Figure 4: Contro l loop of anAC Drive using DTC

Table 1: Comp arison of cont rol variables

The first observation is the similarity between the control blockof the DC drive (Figure 1) and that of DTC (Figure 4).

Both are using motor parameters to directly control torque.

But DTC has added benefits including no feedback device isused; all the benefits of an AC motor (see page 8); and noexternal excitation is needed.

Let us now take a closer look at each of these controlblocks and spot a few differences.


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Evolution of Direct Torque Contro l

As can be seen from Table 1, both DC Drives and DTC drivesuse actual motor parameters to control torque and speed.Thus, the dynamic performance is fast and easy. Also

with DTC, for most applications, no tachometer or encoderis needed to feed back a speed or position signal.

Comparing DTC (Figure 4) with the two other AC drivecontrol blocks (Figures 2 & 3) shows up several differences,the main one being that no modulator is required with DTC.

With PWM AC drives, the controlling variables are frequencyand voltage which need to go through several stagesbefore being applied to the motor. Thus, with PWM drivescontrol is handled inside the electronic controller and not

inside the motor.



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What is Direct Control?

Direct Torque Control - or DTC as it is called - is the verylatest AC drive technology developed by ABB and is set toreplace traditional PWM drives of the open- and closed-looptype in the near future.

Why is it called Direct Torque Control?

Direct Torque Control describes the way in which the control

of torque and speed are directly based on the electromagneticstate of the motor, similar to a DC motor, but contrary to theway in which traditional PWM drives use input frequency andvoltage. DTC is the first technology to control the “real” motorcontrol variables of torque and flux.

What is the advantage of this?

Because torque and flux are motor parameters that are beingdirectly controlled, there is no need for a modulator, as usedin PWM drives, to control the frequency and voltage. This, in

effect, cuts out the middle man and dramatically speeds upthe response of the drive to changes in required torque. DTCalso provides precise torque control without the need for afeedback device.

Why is there a need for another AC drive technology?

DTC is not just another AC drive technology. Industry isdemanding more and existing drive technology cannot meetthese demands.

For example, industry wants:

• Better product quality which can be partly achieved withimproved speed accuracy and faster torque control.

• Less down time which means a drive that will not tripunnecessarily; a drive that is not complicated by expensivefeedback devices; and a drive which is not greatlyaffected by interferences like harmonics and RFI.

• Fewer products. One drive capable of meeting all applicationneeds whether AC, DC or servo. That is a truly “ universal”

drive.• A comfortable working environment with a drive thatproduces much lower audible noise.

General

Chapter 3 - Questions & Answers


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These are just some of the demands from industry. DTCcan deliver solutions to all these demands as well asbringing new benefits to many standard applications.

Who invented DTC?

ABB has been carrying out research into DTC since 1988foll owing the publication of the theory in 1971 and 1985by German doctor Blaschke and his colleague Depenbrock.DTC leans on the theory of field oriented control ofinduction machines and the theory of direct self control.ABB has spent over 100 man years developing thetechnology.

What are the main benefits of DTC technology overtraditional AC drive technology?

There are many benefits of DTC technology. But mostsignificantly, drives using DTC technology have thefollowing exceptional dynamic performance features, manyof which are obtained without the need for an encoder ortachometer to monitor shaft position or speed:

• Torque response: - How quickly the drive output can reach the specif ied value when a nom inal 100% torque

reference step is appl ied.For DTC, a typical torque response is 1 to 2ms below40Hz compared to between 10-20ms for both flux vectorand DC drives fitted with an encoder. With open loopPWM drives (see page 9) the response time is typicallywell over 100ms. In fact , with its torque response, DTChas achieved the natural limit. With the voltage andcurrent available, response t ime cannot be any shorter.Even in the newer “sensorless” drives the torqueresponse is hundreds of milliseconds.

• Accurate torque control at low frequencies, as wellas full load torque at zero speed without the need for afeedback device such as an encoder or tachometer. WithDTC, speed can be controlled to frequencies below 0.5Hzand still provide 100% torque right the way through tozero speed.

• Torque repeatability: - How well the drive repeats its output torque w ith the same torque reference command .DTC, without an encoder, can provide 1 to 2% torque

repeatability of the nominal torque across the speed range.This is half that of other open-loop AC drives and equalto that of closed-loop AC and DC drives.

Performance

Questions and Answers



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• Motor static speed accuracy: - Error between speed reference and actual value at constant load.For DTC, speed accuracy is 10% of the motor slip, which

with an 11kW motor, equals 0.3% static speed accuracy.With a 110kW motor, speed accuracy is 0.1% withoutencoder (open-loop). This satisfies the accuracy requirementfor 95% of industrial drives applications. However, for thesame accuracy from DC drives an encoder is needed.

In contrast, with frequency controlled PWM drives, the staticspeed accuracy is typically between 1 to 3%. So thepotential for customer process improvements issignificantly higher with standard drives using DTCtechnology.

A DTC drive using an encoder with 1024 pulses/revolutioncan achieve a speed accuracy of 0.01%.

• Dynamic speed accuracy: - Tim e integral of speed deviation when a nom inal (100%) torque speed is applied .DTC open-loop dynamic speed accuracy is between 0.3 to0.4%sec. This depends on the gain adjustment of thecontroller, which can be tuned to the process requirements.

With other open-loop AC drives, the dynamic accuracy is

eight times less and in pract ical terms around 3%sec.If we furnish the DTC controller with an encoder, the dynamicspeed accuracy will be 0.1%sec, which matches servodrive performance.

What are the practical benefits of these performancefigures?

• Fast torque response: - This significantly reduces thespeed drop time during a load transient, bringing muchimproved process control and a more consistent productquality.

• Torque control at low frequencies: - This is particularlybeneficial to cranes or elevators, where the load needs tobe started and stopped regularly without any jerking. Alsowith a winder, tension control can be achieved from zerothrough to maximum speed. Compared to PWM fluxvector drives, DTC brings the cost saving benefit that notachometer is needed.

• Torque linearity: - This is important in precision applicationslike winders, used in the paper industry, where an accurateand consistent level of winding is critical.



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• Dynamic speed accuracy: - After a sudden load change,the motor can recover to a stable state remarkably fast.

Apart from excellent dynamic performance figures,

are there any other benefits of DTC drive technology?

Yes, there are many benefits. For example, DTC drives donot need a tachometer or encoder to monitor motor shaftspeed or position in order to achieve the fastest torqueresponse ever from an AC drive. This saves initial cost.


Table 2: Dynamic perform ance features and b enefits offered by DTC technology

Investment cost

savings. Increased

reliability. Better

process control.

Higher product

quality. Leads to a

true universal drive.

Similar performance

to DC but without

tachometer. Reduced

mechanical failures

for machinery. Lessdowntime. Lower

investment.

Cost effective, high

performance torquedrive; provides

position control and

better static

accuracy. High

accuracy control with

standard AC motor.

Investment cost

saving. Better load

control. Can use AC

drive and motor

instead of DC.

Standard AC motor

means less

maintenance and

lower cost.

Allows speed to be

controlled better than

0.5% accuracy. No

tachometer needed in

95% of all applications.

Drive for demanding

applications. Allows

required torque at all

times. Torque

repeatability 1%.Torque response time

less than 5ms.

No mechanical brake

needed. Smooth

transition between

drive and brake.

Allows drive to be

used in traditional DC

drive applications.

Servo drive

performance.

Good motor speed

accuracy without

tachometer.

Excellent torque

control without

tachometer.

Control down to zero

speed and positionwith encoder.

Full torque at zero

speed with or without

tachometer/encoder.

FEATURE RESULT BENEFIT



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Table 3: User features and benefits offered b y DTC technolog y

Rapid control DC link

voltage.

Power loss ride through. Drive will not trip. Less

down time. Avoidsprocess interruptions.

Less waste in

continuous process.

Automatic start

(Direct restart).

Starting with motor

residual induct ance

present. No restarting

delay required.

Can start into a motor

that is running without

waiting for flux to decay.

Can transfer motor from

line to drive. No restart.

No interruptions on

process.

Controlled braking

between two speed

points.

Investment cost savings.

Better process control.

No delay required as in

DC braking. Can be

used for decelerating to

other than zero speed.

Reduced need for brake

chopper and resistor.

Flux braking.

Flux op tim isat ion. Motor losses minim ised.Less motor noise.

Controlled mot or.

Self identification/

Auto-tuning.

Tuning the motor to

drive for top

performance.

Easy and accurate set-

up. No parameter tuning

required. Less

commissioning time.

Guaranteed starting

torque. Easy retrofit for

any AC system.

No predetermined

switching pattern of

power devices.

Low noise. No fixed

carrier, therefore

acoustic noisereasonable due to

“white” noise spectrum.

Cost savings in acoustic

barriers in noise

sensitive applications.No harmful mechanical

resonances. Lower

stresses in gearboxes,

fans, pumps.

Can accelerate and

decelerate in quickest

time possible without

mechanical constraints.

Automatic start

(Flying start).

Synchronises to rotating

motor.

No process

interruptions. Smooth

control o f machinery.Resume control in all

situations.

No limits on maximum

acceleration and

deceleration rate.

Better process control.

BENEFITFEATURE RESULT


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Also a DTC drive features rapid starting in all motorelectromagnetic and mechanical states. The motor canbe started immediately without delay.

It appears that DTC drives are most advantageous forhigh performance or demanding drive applications. Whatbenefits does DTC bring to standard drives?

Standard applications account for 70% of all variable speeddrives installed throughout industry. Two of the most commonapplications are in fans and pumps in industries like Heating,Ventilating and Air Condit ioning (HeVAC), water and food anddrinks.

In these applications, DTC provides solutions to problemslike harmonics and noise.

For example, DTC technology can provide control to the driveinput line generating unit, where a conventional diode bridgeis replaced with a controlled bridge.

This means that harmonics can be significantly reducedwith a DTC controlled input bridge. The low level currentdistortion with a DTC controlled bridge will be less than aconventional 6-pulse or 12-pulse configuration and power

factor can be as high as 0.99.

For standard applications, DTC drives easily withstand hugeand sudden load torques caused by rapid changes in theprocess, without any overvoltage or overcurrent trip.

Also, if there is a loss of input power for a short time, thedrive must remain energised. The DC link voltage must notdrop below the lowest control level of 80%. To ensure this,DTC has a 25 microseconds control cycle.

What is the impact of DTC on pump control?

DTC has an impact on all types of pumps. Because DTCleads to a universal drive, all pumps, regardless of whetherthey are centrifugal or constant torque type (screw pumps)can now be controlled with one drive configuration, ascan aerators and conveyors. DTC technology allows a driveto adjust itself to varying application needs.

For example, in screw pumps a drive using DTC technologywill be able to adjust itself for sufficient starting torque for aguaranteed start.




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Improved power loss ride through will improve pumpingavailability during short power breaks.

The inherent torque control facility for DTC technology allowsthe torque to be limited in order to avoid mechanical stresson pumps and pipelines.

What is the impact of DTC technology on energysavings?

A feature of DTC which contributes to energy efficiency is adevelopment called motor flux opt imisation.

With this feature, the efficiency of the total drive (that is

controller and motor) is greatly improved in fan and pumpapplications.

For example, with 25% load there is up to 10% total energyefficiency improvement. At 50% load there can be 2% totalefficiency improvement.

This directly impacts on operating costs. This feature alsosignificantly reduces the motor noise compared to thatgenerated by the switching frequency of a traditional PWMdrive.

Has DTC technology been used in many installations?

Yes, there are hundreds of thousands of installations in use.For example, one of the world' s largest web machinemanufacturers tested DTC technology for a winder in afilm finishing process.

The Requirement:Exact torque control in the winder so as to produce highquality film rolls.

The Solution:Open-loop DTC drives have replaced t raditional DC drivesand latter flux vector controlled AC drives on the centredrives in the rewind station.



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The Benefits:Winder station construction simplified and reliability increased.The cost of one tachometer and associated wiring equals that

of one 30kW AC motor. This provides significant investmentcost savings.

What is the difference between DTC and traditionalPWM methods?

• Frequency Control PWM and Flux Vector PWM

Traditional PWM drives use output voltage and outputfrequency as the primary control variables but these needto be pulse width modulated before being applied to the

motor.

This modulator stage adds to the signal processing time andtherefore limits the level of torque and speed responsepossible from the PWM drive.

Typically, a PWM modulator takes 10 times longer than DTCto respond to actual change.

• DTC control

DTC allows the motor’s torque and stator flux to be usedas primary control variables, both of which are obtaineddirectly from the motor itself. Therefore, with DTC, there isno need for a separate voltage and frequency controlledPWM modulator. Another big advantage of a DTC drive isthat no feedback device is needed for 95% of all driveapplications.

Why does DTC not need a tachometer or position encoderto tell it precisely where the motor shaft is at all times?

There are four main reasons for this:

• The accuracy of the Motor Model (see page 27).• Controlling variables are taken directly from the motor

(see page 27).• The fast processing speeds of the DSP and Optimum

Pulse Selector hardware (see page 28).• No modulator is needed (see page 12).

Operation




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When combined to form a DTC drive, the above featuresproduce a drive capable of calculating the ideal switchingvoltages 40,000 times every second. It is fast enough to

control individual switching pulses. Quite simply, it is thefastest ever achieved.

Once every 25 microseconds, the inverter’s semiconductorsare supplied with an optimum switching pattern to producethe required torque. This update rate is substantially lessthan any time constants in the motor. Thus, the motor isnow the limiting component, not the inverter.

What is the difference between DTC and othersensorless drives on the market?

There are vast differences between DTC and many of thesensorless drives. But the main difference is that DTCprovides accurate control even at low speeds and down tozero speed without encoder feedback. At low frequenciesthe nominal torque step can be increased in less than1ms. This is the best available.

How does a DTC drive achieve the performance of aservo drive?

Quite simply because the motor is now the limit ofperformance and not the drive itself. A typical dynamic speedaccuracy for a servo drive is 0.1%s. A DTC drive can reachthis dynamic accuracy with the optional speed feedbackfrom a tachometer

How does DTC achieve these major improvementsover traditional technology?

The most st riking difference is the sheer speed by whichDTC operates. As mentioned above, the torque response is

the quickest available.

To achieve a fast torque loop, ABB has utilised the latesthigh speed signal processing technology and spent 100 manyears developing the highly advanced Motor Model whichprecisely simulates the actual motor parameters withinthe controller.

For a clearer understanding of DTC control theory, seepage 26.



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Does a DTC drive use fuzzy logic within its control loop?

No. Fuzzy logic is used in some drives to maintain the

acceleration current within current limits and therefore preventthe drive from tripping unnecessarily. As DTC is controllingthe torque directly, current can be kept within these limitsin all operating conditions.

A drive using DTC technology is said to be tripless.How has this been achieved?

Many manufacturers have spent years trying to avoid tripsduring acceleration and deceleration and have found itextraordinarily difficult. DTC achieves tripless operation

by controlling the actual motor torque.

The speed and accuracy of a drive which relies oncomputed rather than measured control parameters cannever be realistic. Unless you are looking at the shaft,you are not getting the full picture. Is this true withDTC?

DTC knows the full picture. As explained above, thanks tothe sophistication of the Motor Model and the ability to carryout 40,000 calculations every second, a DTC drive knows

precisely what the motor shaft is doing. There is never anydoubt as to the motor’s state. This is reflected in theexceptionally high torque response and speed accuracyfigures quoted on pages 16 and 17.

Unlike traditional AC drives, where up to 30% of all switchingsare wasted, a drive using DTC technology knows preciselywhere the shaft is and so does not waste any of its switchings.

DTC can cover 95% of all industrial applications. Theexceptions, mainly applications where extremely precisespeed control is needed, will be catered for by adding afeedback device to provide closed loop control. This device,however, can be simpler than the sensors needed forconventional closed loop drives.

Even with the fastest semiconductors some dead timeis introduced. Therefore, how accurate is the auto-tuning of a DTC drive?

Auto-tuning is used in the initial identification run of a DTC

drive (see page 27). The dead t ime is measured and is takeninto account by the Motor Model when calculating the actualflux. If we compare to a PWM drive, the problem with PWMis in the range 20-30Hz which causes torque ripple.




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What kind of stability will a DTC drive have at lightloads and low speeds?

The stability down to zero speed is good and both torqueand speed accuracy can be maintained at very low speedsand light loads. We have defined the accuracies as follows:

Torque accuracy: Within a speed range of 2-100% and aload range of 10-100%, the torque accuracy is 2%.

Speed accuracy: Within a speed range of 2-100% and aload range of 10-100%, the speed accuracy is 10% of themotor slip. Motor slip of a 37kW motor is about 2% whichmeans a speed accuracy of 0.2%.

What are the limitations of DTC?

If several motors are connected in parallel in a DTC-controlledinverter, the arrangement operates as one large motor. It hasno information about the status of any single motor. If thenumber of motors varies or the motor power remains below1/8 of the rated power, it would be best to select the scalarcontrol macro.

Can DTC work with any type of induction motor?

Yes, any type of asynchronous, squirrel cage motor.



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Figure 5, below, shows the complete block diagram forDirect Torque Control (DTC).

Walk around the block

The block diagram shows that DTC has two fundamentalsections: the Torque Control Loop and the Speed Control

Loop. Now we will walk around the blocks exploring eachstage and showing how they integrate together.

Let’s start with DTC’s Torque Control Loop.

How DTC works

Figure 5: DTC comprises two key blocks: Speed Cont rol and Torqu e Control

Chapter 4 - Basic Contro l Theory



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In normal operation, two motor phase currents and theDC bus voltage are simply measured, together with theinverter’s switch positions.

The measured information from the motor is fed to theAdaptive Motor Model.

The sophistication of this Motor Model allows precise dataabout the motor to be calculated. Before operating theDTC drive, the Motor Model is fed information about the

motor, which is collected during a motor identification run.This is called auto-tuning and data such as statorresistance, mutual inductance and saturation coefficientsare determined along with the motor’s inertia. Theidentification of motor model parameters can be donewithout rotating motor shaft. This makes it easy to applyDTC technology also in retrofits. The extremely fine tuningof motor model is achieved when the identification runalso includes running the motor shaft for some seconds.

There is no need to feed back any shaft speed or positionwith tachometers or encoders if the static speed accuracyrequirement is over 0.5%, as it is for most industrial applications.

Torque Control Loop

Step 1 Voltage and current measurements

Step 2 Adaptive Motor Model

Basic Control Theory


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This is a significant advance over all other AC drivetechnology. The Motor Model is, in fact, key to DTC’sunrivalled low speed performance.

The Motor Model outputs control signals which directlyrepresent actual motor torque and actual stator flux. Alsoshaft speed is calculated within the Motor Model.

The information to control power switches is produced inthe Torque and Flux Comparator.

Both actual torque and actual flux are fed to the comparatorswhere they are compared, every 25 microseconds, to a torqueand flux reference value. Torque and flux status signals are

calculated using a two level hysteresis control method.

These signals are then fed to the Optimum Pulse Selector.

Within the Optimum Pulse Selector is the latest 40MHzdigital signal processor (DSP) together with ASIC hardwareto determine the switching logic of the inverter. Furthermore,all control signals are transmitted via opt ical links for highspeed data transmission.

This configuration brings immense processing speed such

that every 25 microseconds the inverter’s semiconductorswitching devices are supplied with an optimum pulse forreaching, or maintaining, an accurate motor torque.

The correct switch combination is determined every controlcycle. There is no predetermined switching pattern. DTC hasbeen referred to as “just-in-time” switching, because,unlike traditional PWM drives where up to 30% of all switchchanges are unnecessary, with DTC each and everyswitching is needed and used.

This high speed of switching is fundamental to the success ofDTC. The main motor control parameters are updated 40,000times a second. This allows extremely rapid response on theshaft and is necessary so that the Motor Model (see Step2) can update this information.

It is this processing speed that brings the high performancefigures including a static speed control accuracy, withoutencoder, of ±0.5% and the torque response of less than 2ms.

Step 4 Opt imum Pulse Selecto r

Step 3 Torque Comparator and Flux Comparator




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Within the Torque Reference Controller, the speed controloutput is limited by the torque limits and DC bus voltage.

It also includes speed control for cases when an externaltorque signal is used. The internal torque reference from thisblock is fed to the Torque Comparator.

The Speed Controller block consists both of a PID controllerand an acceleration compensator. The external speedreference signal is compared to the actual speed produced

in the Motor Model. The error signal is then fed to both thePID controller and the acceleration compensator. The outputis the sum of outputs from both of them.

An absolute value of stator flux can be given from the FluxReference Controller to the Flux Comparator block. The abilityto control and modify this absolute value provides an easyway to realise many inverter functions such as FluxOptimisation and Flux Braking (see page 19).

Speed Control

Step 5 Torque Reference Controller

Step 6 Speed Controller


Step 7 Flux Reference Controller


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Chapter 5 - Index

AAC drive 5, 6, 8, 9, 10, 12, 13, 14,15, 16, 17, 18, 21, 24, 28AC drive using DTC 12, 13AC drive with flux vector control 10AC drive with frequency control 9AC induction motor 10, 11AC motor 5, 6, 8, 13, 18AC variable speed drive 6, 8acceleration compensator 29accuracy control 18aerators 20air condition 5, 20

angular posit ion 11armature current 7armature windings 7ASIC 28auto-tuning 19, 24, 27

BBlaschke 16braking 19, 29

Cclosed-loop 10, 11, 15, 16closed-loop drives 10, 11commissioning 19

commutator-brush assembly 7control cycle 28control loop 7, 9, 10, 12, 13, 24,26, 27, 29control variables 10, 13, 15, 22controlled input bridge 20controlling variables 9, 11, 12, 14,22conveyors 20costs 8, 10, 11, 18, 19, 21

DDC bus voltage 27, 29DC drive 7, 8, 9, 10, 11, 12, 13,

14, 18DC link voltage 19, 20DC motor 6, 7, 8, 11, 15DC Motor Drive 6Depenbrock 16digital signal processing 12diode bridge 20diode rectifier 9Direct Torque Control 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 26drive input line generating unit 20DSP 22, 28DTC 5, 6, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28dynamic speed accuracy 12, 17,18, 23dynamic speed response 8

Technical Guide No.1- Direct Torque Cont rol

Eelectrical time constant 8electronic controller 11, 14elevators 17encoders 8, 11, 12, 14, 18, 22,23, 27, 28energy savings 21external speed reference 29external torque signal 29

Ffan 10, 19, 20, 21feedback device 9, 10, 11, 13,

15, 16, 22, 24field current 7field orientation 7, 8, 10, 11, 12field oriented control 16film finishing 21flux braking 19, 29flux comparator 28, 29flux opt imisation 19, 21, 29Flux Reference Controller 29flux vector 6, 10, 11, 13, 16, 21, 22flux vector control 6, 10, 11, 13flux vector PWM drives 11food 20frequency control 6, 9, 13, 22

fuzzy logic 24

Ggearbox 19

Hharmonics 15, 20heating 20HeVAC 20hysteresis control 28

Iinertia 27initial cost 18

input frequency 15

Lload torque 16, 20loss of input power 20low frequencies 16, 17, 23

Mmagnetising current 7maintenance 6, 8, 18mechanical brake 18modulator 9, 10, 11, 12, 14, 22motor controller 8motor flux optimisation 21motor magnetising flux 12Motor Model 10, 22, 23, 24, 27,28, 29motor noise 19, 21Motor static speed 17

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motor torque 8, 12, 28mutual inductance 27

Nnoise 15, 19, 20, 21nominal torque step 23

OOEMs 5open-loop drive 9open loop AC drives 12operating cost 21optical link 28

Optimum Pulse Selector 28output frequency 22output voltage 22

Ppaper industry 17PID controller 29pipelines 21position control 18posit ion encoder 12, 22position feedback 8power factor 20power loss ride through 19, 21predetermined switching pattern 19,

28Pulse Width Modulation 9pump 10, 19, 20, 21PWM 6, 9, 10, 11, 14, 15, 16, 17,21, 22, 24, 28PWM AC drive 11, 14, 21, 22, 24,28

Rreliability 8, 18restart 19retrofit 19RFI 15rotor 7, 8, 10, 11

rotor flux 11rotor position 7rotor speed 11

Ssaturation coefficient 27scalar control 10, 25sensorless 23servicing 8servo drive 18, 23signal processing 12, 22, 23signal processing time 22speed 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 20, 22, 23, 24,25, 26, 27, 28, 29speed accuracy 6, 8, 11, 12, 15,17, 18, 23, 24, 25, 27speed cont rol 6, 7, 24, 26, 28, 29Speed Control Loop 26

speed control output 29Speed Controller 29speed response 7, 8, 22stability 25start 5, 19, 20, 26start ing 19, 20static accuracy 18static speed accuracy 17, 27stator 7, 9, 10, 11, 22, 27, 28, 29stator field 11stator flux 22, 28, 29stator resistance 27stator winding 9, 10

stress 19, 21switching pattern 19, 23, 28switching pulses 23

Ttachometer 12, 14, 16, 17, 18,22, 23, 27time constant 8, 23torque 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 28, 29- control 5, 6, 7, 8, 10, 12, 18, 21,26- control at low frequencies 16

- full load at zero speed 16- linearity 17- loop 23- repeatability 18- response 6, 8, 11, 12, 18, 23,24, 28- ripple 24Torque and Flux Comparator 28Torque Comparator 28, 29Torque Control Loop 26Torque Reference Controller 29trip 15, 19, 20, 24

U

universal 12, 15, 18, 20

Vvariable speed drives 5, 6, 13,20ventilating 20voltage 8, 9, 10, 11, 14, 15, 16,19, 20, 22, 23, 27, 29voltage fed drive 8VSD 5, 6

Wwater 5, 20web machine 21winder 17, 21, 22

Zzero speed 11, 16, 18, 19, 23, 25

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ABB OyD rives

P.O . B ox 184FIN -00381 H elsinkiFIN LAN D

Tel: +358 10 22 11Fax: +358 10 222 2681Internet: http://w w w .abb.com /m otors&drives

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Technical Guide No. 2Technical Guide No. 2

EU Council Directives andAdjustable Speed Electrical PowerDrive Systems


40/316Technical Guide No.2- EU Cou ncil Directives 2


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Contents

1 Introduction .........................................................7This guide’s purpose .................................................... 7How to use this guide .................................................. 8

Responsibilities and actions..................................... 8Tickboxes ................................................................. 8Cross-referencing .................................................... 8Key Points ................................................................ 8

2 General questions and answers ...........................9What is all the fuss about? ........................................... 9

What are these EU Council Directives? .................... 9

How does EMC affect me? ...................................... 9What is EMC? ........................................................ 10What is an electromagnetic environment? ............. 10How does electromagnetic interference show up? 10What emissions can drives cause? ........................ 11How is this emission seen? .................................... 11How do I avoid electromagnetic interference? ...... 11Drive manufacturers must comply with EMCstandards then? ..................................................... 11If a drive is CE Marked, I need not worry. True?..... 11

3 CE Marking ........................................................ 13What is CE Marking and how relevant is it for drives? 13What is CE Marking for? ............................................ 14

Is CE Marking a quality mark? ............................... 14What is the legal position regarding CE Marking? . 14What is the importance of CE Marking forpurchasers of drives? ............................................. 14If I buy a CE marked drive, will I meet thetechnical requirements of the Directives? .............. 14What happens if, as an End User, I put together asystem - do I have to put CE Marking on? ............. 15

What about spare parts that I buy for a drive? Do Inegate the CE Mark if I replace a component? ...... 15If drives are classed as components, they cannotbe EMC certified or carry a CE Mark, is this true? . 15

In Summary ................................................................ 16Component ............................................................ 16Components with direct function ........................... 16Components without direct function ...................... 17Apparatus .............................................................. 17Systems ................................................................. 17Installation .............................................................. 17

4 Purchasing decisions for PDSs .......................... 18What you need to know and do ................................. 18If you are a Machine Builder buying a PDS ............. 22

Technical Guide No.2- EU Cou ncil Directives

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Actions you must take ........................................... 23If you are a System Designer buying a PDS............... 26

Path 1 ..................................................................... 26Actions you must take ........................................... 27Path 2 ..................................................................... 27Actions you must take ........................................... 27Path 3 ..................................................................... 28Actions you must take ........................................... 28

If you are an End-User buying a CDM/BDM or PDS .. 28You have the following responsibilities ................... 29Actions you must take ........................................... 29

If you are a Panelbuilder buying a CDM/BDM............ 30Additional actions .................................................. 32

If you are a Distributor buying a CDM/BDM ............... 32If you are an Installer buying a CDM/BDM or PDS..... 32

5 Terminology ....................................................... 34Technical Construction File (TCF)............................... 34

What is a Technical Construction File? .................. 34When do I use a TCF?............................................ 34Why is a TCF deemed to be important? ................ 34Will customers always receive a TCF copy? .......... 35What is the shelf life of a TCF? .............................. 35Is there any way I can avoid the TCF? ................... 35How do I ensure that tests are always carried out? 35

Can drive manufacturers help more? ..................... 35How to make up a TCF .............................................. 361. Description of the product ................................. 362. Procedures used to ensure product conformity . 373. A report or certificate from a Competent Body .. 374. Actions by the Competent Body ........................ 38

Technical File (for mechanical safety aspects) ........... 38What is a Technical File? ........................................ 38

How to make up a Technical File ............................... 39Drawings and diagrams ......................................... 39Health and safety ................................................... 39

Machine design...................................................... 39Other certificates required ..................................... 39Technical File (for electrical safety aspects) ............... 40

What is a Technical File? ........................................ 40How to make up a Technical File ............................... 40

Drawings and diagrams ......................................... 40Standards............................................................... 40Electrical Safety Aspect ......................................... 40Other requirements ................................................ 40

Certificate of Adequacy ............................................. 41What if standards cannot be wholly implemented? 41

How to obtain a Certificate of Adequacy ................... 41Technical Report or Certificate ................................... 41What if standards cannot be wholly implemented? 41

How to obtain the Technical Report or Certificate ..... 41

Technical Guide No.2- EU Cou ncil Directives 4


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Report ........................................................................ 41What if standards cannot be wholly implemented? 41

How to obtain a Report .............................................. 42Declaration of Conformity (for EMC and electricalsafety aspects) ........................................................... 42How to obtain a Declaration of Conformity ................ 42Declaration of Conformity (for mechanicalsafety aspects) ........................................................... 43How to obtain a Declaration of Conformity ................ 43Declaration of Incorporation ...................................... 43

What is a Declaration of Incorporation?................. 43Is there no way out of this type of Declaration?..... 44

What a Declaration of Incorporation contains............ 44Type Certification ....................................................... 45How to obtain Type Certification ................................ 45

6 Authorities and Bodies ....................................... 46Competent Authority .................................................. 46Competent Body ........................................................ 46Notified Body ............................................................. 46

7 Standards and Directives ................................... 47Directive or Standard? ............................................... 47Harmonised Standards for PDSs ............................... 47

How to recognise a European Standard ................ 48

Your questions answered ........................................... 48Which standards directly relate to drives? ............. 48What are the issues of EN 61800-3 and drives? .... 49What are the solutions to radiated emissions? ...... 49Do I have to conform to the standards? ................ 49Can I be fined for not conforming? ........................ 50

The Product Specific Standard EN 61800-3............... 50Mode 1 ................................................................... 50Mode 2 ................................................................... 50Mode 3 ................................................................... 51Mode 4 ................................................................... 51

Applications of different Modes ................................. 51Machinery Directive 98/37/EC.................................... 52How does the Machinery Directive affect my drive?52Where can I obtain a Machinery Directive copy? ... 53

Low Voltage Directive ................................................. 53How does the LVD affect my drive? ....................... 53Why is the Declaration of Conformity important? .. 54

EMC Directive ............................................................ 54How does the EMC Directive affect my drive?....... 54Who has the responsibility to ensure CE Marking? 55Summary of responsibilities ................................... 56

Achieving conformity with EC Safety Directives .... 57

8 Installation ......................................................... 58General installation concerns ..................................... 58


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Technical requirements of the legislation ................... 58How can EMC be improved? ................................. 59

General installation practice ....................................... 60Cabling ................................................................... 60Relay Outputs ........................................................ 60Earthing .................................................................. 61Shielding ................................................................ 62Filtering .................................................................. 63Testing and installation ........................................... 64

Your technical concerns answered ............................ 65What is the affect of varying impedance? .............. 65What are the effects of multiple drives? ................. 65Large installations with many drives can take upto 3 months and be costly. What can we do? ........ 65

9 Index ................................................................. 66



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Chapter 1 - Introduct ion

This guide' s purpose


2

7

The aim of this Technical Guide No.2* is to give a straight-forward explanation of how the various EU Council Directivesrelate to Power Drive Systems (PDSs). For an explanationof the terminology of PDSs, see pages 18 and 19.

While Electromagnetic Compatibility (EMC) is the subjectof most concern within the industry, it must be realisedthat the EMC Directive is only part of the overall EU initiativeon common safety standards.

It is the intention of this Guide to offer users of AC or DCpower drive systems - whether Machine Builders, SystemDesigners, Distributors, OEMs, End-Users or Installers -some clear practical guidelines and courses of action.

*Notes

1 The content of this Technical Guide is ABB Oy's, Drivesinterpretation of events as of November 1999. However,we reserve the right to develop and evolve theseinterpretations as more details become available from

Competent Bodies (see Chapter 6), CompetentAuthorities (see Chapter 6), organisations and from ourown tests.

2 Other Technical Guides available in this series include:

Technical Guide No.1 -Direct Torque Control (3AFE 58056685).

Technical Guide No.3 -EMC Compliant Installation and Configuration for a

Power Drive System (3AFE 61348280).

Technical Guide No.4 -Guide to Variable Speed Drives (3AFE 61389211).

Technical Guide No.5 -Bearing Currents in Modern AC Drive Systems(3BFE 64230247)

Technical Guide No.6 -Guide to Harmonics with AC Drives (3AFE 64292714)

Technical Guide No.7 -Dimensioning of a Drive system (3AFE 64292714)

Technical Guide No.8 -Electrical Braking (3BFE 64362534)


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The Guide is divided into 9 Sections.

Section 4 looks at Purchasing Decisions for PDSs.

Please note the following about the structure of thissection:

Each type of purchaser is offered an explanation of theirResponsibilities. This is for awareness. No action is needed.

Following the Responsibilities is a set of Actions. If thepurchaser follows these Actions, step-by-step, thenconforming to the relevant Directives will be straightforward.

Alongside the Actions are tickboxes. Purchasers can

photocopy the relevant pages and use them as a checklistwith each item being ticked off as it is achieved.

Because of the complexity of conforming to each Directive,this Guide inevitably carries a lot of cross-references toother sections. In the margin you will come across:

Defined on page XXYou are advised to turn to the page number reference.

You will also notice other references within the text. These

can be referred to if the item is unclear but is not essentialfor achieving compliance.

Within the text you will see:

Key PointThese are key observations that must be observed.

How to Use this Guide

Responsibilities and actions

Tickboxes

Cross- referencing

KEY POINTS:



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Chapter 2 - General questions and answers

What is all the fuss about?

I have had no problems with drives in the past so whydo I need to be concerned with EMC now?

Beware! Electromagnetic Compatibility (EMC) is only oneof a number of EU Council Directives relating to commonsafety standards for electrically powered equipment likePower Drive Systems.

It is very important that users of PDSs fully understand allthe various rules and regulations and how they apply to

PDSs. That is the purpose of this Guide.

It is important to realise that EMC cannot be divorced fromother European legislation. So before answering thisquestion, we need to look at the other legislation and howit affects the purchase and installation of drives.Quite simply there are three Directives that mainly affecta drive’s safety against risks and hazards. These are:

But more on each of these Directives later. Let us firstexplain EMC and look at some concerns of the industry.

From January 1, 1996 the EU Council’s ElectromagneticCompatib ility Directive (89/336/EEC) has been compulsory.

It applies to all electrical and electronic equipment soldwithin the EU and affects virtually all manufacturers andimporters of electrical and electronic goods.

KEY POINT:

What are these EU Council Directives?

How d oes EMC

affect me?

Direc t ive App l ic ab le M andat o r y Page

Mach iner y Dir ec t ive 1993 -01 -01 1995 -01 -01 pg 52

Low Vo l t age Dir ec t ive 1995 -01 -01 1997 -01 -01 pg 53

EMC Direc t ive 1992 -01 -01 1996 -01 -01 pg 54


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Electrical equipment that does not conform to theregulations may not be sold anywhere in the EEA (EuropeanEconomic Area).

EMC stands for Electromagnetic Compatibility. It is theability of electrical/electronic equipment to operateproblem-free within an electromagnetic environment.Likewise, the equipment must not disturb or interfere withany other products or systems within its locality.

The electromagnetic environment is everywhere but itvaries from place to place. The reason is that there aremany different sources of disturbance which can be naturalor man-made.

Natura l sources consist of electrical discharge betweenclouds, lightning or other atmospheric disturbances. Whilewe cannot influence these sources we can protect ourproducts and systems from their effects (see Installation,page 58).

Man -m ade d i st u rbances are those generated by, forexample, electrical contacts and semiconductors, digitalsystems like microprocessors, mobile radio transmitters,walkie-talkies, portable car telephones and Power Drive

Systems (see page 18).

Such a variety of equipment, each with its own emissioncharacteristics, is often used so near to other electricalequipment that the field strengths they create may causeinterferences.

It is important that all PDSs are immune to these naturaland man-made disturbances. While drives manufacturersstrive to make their products immune, the Directive laysdown minimum standards for immunity, thereby ensuring

all manufacturers achieve the same basic level.

Electromagnetic interference shows up in a variety of ways.Typical examples of interference include a poorlysuppressed automobile engine or dynamo; an electric drillcausing patterning on the TV screen; or crackling from anAM radio.

The microprocessor and power electronic component,switch rapidly and therefore, can cause interference at highfrequencies, unless proper precautions are taken.

KEY POINT:

What is EMC?

What is an electromagnetic environment?

KEY POINT:

How does electromagnetic interference show up?



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The normal operation of any drive involves rapid switchingof high voltages and this can produce radio frequencyemission. It is this radiation and emission that have been

seen to have the potential to disturb other circuits atfrequencies below 200 MHz.

Modern equipment contains considerable communicationsand other digital electronics. This can cause considerableemissions at frequencies above 200MHz.

The main emission is via conduct ion to the mains. Radiationfrom the converter and conducting cables is another typeof emission and it is especially demanding to achieve theradiated emission limits.

You need to ensure two things:

• that the equipment generates minimum emission.

• that the equipment is immune to outside effects.

In the case of Power Drive Systems, a lot hinges on thequality of the installation. See Installation, page 58, formore details.

Electromagnetic interference needs to be conducted toearth (ground potential) and no system can work unless itis properly connected.

Unfortunately, the process is not that simple. Virtuallyeveryone in the supply chain has a responsibility to ensurea product, a system and an installation complies with theessential requirements of the EMC Directive.

The key is to c learly understand who has responsibility forwhat. In the forthcoming pages we take a look at various

types of purchasers and examine the steps each shouldtake to meet all three Directives mentioned on page 9.

Everyone from manufacturer to installer to user has aresponsibility in complying with EMC rules.

Again this is a big misconception. Just because a drivehas CE Marking does not necessarily mean it meets theEMC Directive.

How is this emission seen?

How do I avoid electromagnetic interference?

KEY POINT:

Drives manufacturers must comp ly wi th EMC standards

then?

If a dr ive is CE Marked, I need not w orry.True?

What em issions can drives cause?


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This will all become clear by referring to the sectionPurchasing Decisions for PDSs, page 18.

CE Marking according to the EMC-Directive cannotnormally be applied to a module that is no more than achassis with exposed terminals.

KEY POINT:



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Chapter 3 - CE Marking

What is CE Marking and how relevant is it for d rives?

CE Marking, shown below, is the official signature of theDeclaration of Conformity (see pages 42 and 43) asgoverned by the European Commission. It is a very specificgraphic symbol and must be separated from other marks.

CE Marking is a system of self-certification to identify

equipment that complies with the relevant applicableDirectives.

If a drive is the subject of several directives and, forexample, conforms with the Low Voltage Directive (seepage 53), then, from 1997, it is compulsory that it showsCE Marking. That marking shall indicate that the drivealso conforms to the EMC Directive (page 54). CE markingshall indicate conformity only to the directive(s) appliedby the manufacturer.

NOTE: If the standards route is used, then there must be aTechnical File supporting the Declaration of Conformity.However, if standards cannot be complied with then aTechnical Construction File (TCF) needs to be compiled.

For more on Technical Construction Files and TechnicalFiles, please refer to pages 34 and 40.

KEY POINT:


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What is CE Marking for?

CE Marking is mainly for the benefit of Authoritiesthroughout the EU and EEA countries who control themovement of goods. CE Marking shows that the product

complies with the essential requirements of all relevantDirectives, mainly in the area of technical safety andconformity assessment. There are three Directives that arerelevant to drives, but CE Marking may be attached toindicate compliance with one (see the previous page).

Most definitely not. As CE Marking is self certif ication,you can be assured that certification has been carried out.

Anyone applying CE Marking is legally liable and must beable to prove the validity of his actions to the authorities.

CE Marking confirms compliance with the Directives listedin the Declaration of Conformity (see pages 42 and 43).

As far as a purchaser of a drive is concerned, anythingthat carries the CE Mark must have a functional valueto him.

Thus, a complete drive product, which can be safelycabled and powered up on its own, may carry the CEmarking.

In practice, you will see drive products with CE Marking.But it is important to understand just why the product wasgiven CE Marking in the first place.

Basically a drive has no functional value. It is only ofpractical use when connected to, say, a motor which inturn is connected to a load.

Therefore, as far as the Machinery Directive is concerneda drive cannot have CE Marking unless it is part of a“process” comprising the drive, motor and load.

As for the EMC Directive, the equipment that make up a“process” include cabling, drives and motor. CE Markingcan only be affixed if all items forming such a “process”conform to the requirements of the Directive.

However, in the eyes of the Low Voltage Directive, a builtdrive does have functionality. That is, through the drive'sParameters you can program the drive and obtain an inputand output signal. Thus, if a drive conforms to the LowVoltage Directive

it can carryCE Marking.

Refer to pages52, 53 and 54 for explanations of the three Directives.

Is CE Marking a quality mark?

What is the legal position regarding

CE Marking?

What is the importance of CE Marking for pu rchasers of drives?

If I buy a CE marked drive,w ill I meet the technical requirements of the Directives?



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Yes. Anyone putting together a system and commissioningit is responsible for the appropriate CE Marking.

Turn to page 29 for more details about the End-User'sresponsibilities.

Equipment supplied before the application of theDirectives, can be repaired and supplied with spare partsto bring it back to the original specification. However, it

cannot be enhanced or reinstalled without meeting theDirectives.

For equipment supplied after the application of theDirectives, the use of the manufacturer's spare partsshould not negate the CE Marking. However, themanufacturer or supplier should be consulted aboutupgrading, as some actions could affect the CE Markingcriteria.

You need to first understand the terminology now being

applied to drives. See below and page 18 for this.

A Complete Drive Module (CDM) is normally a componentin a system and as such has no funct ional value unless itis connected to the motor when it becomes a PDS.

The CDM shall be CE-marked if it is to be installed withsimple connections and adjustments that do not requireany EMC-knowledge.

If awareness of the EMC implication is needed in order to

install a CDM, it is not considered as an apparatus. Thus,it shall not be CE-marked according to the EMC-directives.

If a CDM or BDM is intended for incorporation in PDS byprofessional manufacturers only (panel builders, machinebuilders), it shall not be CE-marked, nor is declaration ofconformity given by the CDM/BDM manufacturer. Insteadinstallation instructions shall be supplied in order to helpthe professional manufacturers.

KEY POINT:

What happens if,as an End-User,I put together a

system - do I have to put CE Marking on?

What about spare parts that I buy for a drive? Do I negate the CE Mark if I replace a component?

If drives are

classed as components,they cannot be EMC certif ied or carry a CE Mark. Is this true?


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In Summ ary Under the Directives, Components with direct functionavailable without further adjustment other than simpleones, Apparatus and Systems have to be CE marked.

Components with direct function not available withoutsimple adjustments and Components without directfunction and Installations, while required to satisfyvarious elements of the Directives, shall not be CE marked.

In this context the interpretation of component can bedivided into two main categories. The component caneither deliver a ‘direct function’ or not.

Direct function:Any funct ion of the component i tself , whic h ful f ils the

in tended use , spec i f i ed by the m anu fac tu re r in the instruct ion for use for an end user.

Components with a direct function can be divided into twosub-groups:

1 ) Th e d ir ec t fu n c tio n i s a va i l a b l e w i t hou t fu r t he r a d j u stm en t o r c o n n e c t i o n s o t h e r t h a n s im p l e o ne s, which can be performed b y any person not fully aware of the EMC imp l ica t ions . Such a com po nent is an ‘apparatus’ and it is subjected to all provisions

of the EMC Direct ive.

2 ) The d ir ec t func t ion i s no t ava i l ab le wi thout fur ther adjustment or c onnect ions other than s im ple ones,which c an be perform ed by any person not fully aware of the EMC imp lications. Such a com ponent is not an ‘ a p p a r a t u s ’ . T h e o n l y r eq u i r em en t f o r s u c h a comp onent is to prov ide i t wi th inst ruct ions for use for the p rofessional assembler or m anufacturer of the f inal app aratus into which the compon ent wi l l be incorporated. These inst ruct ions should help him

to solve any EMC p rob lems w i th his f inal app aratus.

If a component performs a direct function without furtheradjustment other than simple ones, the component isconsidered equivalent to apparatus. Some variable speedpower drive products fall into this category, e.g. a driveinstalled into a cabinet or drive with enclosure and sold as acomplete unit (CDM). All provisions of the EMC Directive apply.

If a component performs a direct function that is not availablewithout further adjustment other than simple ones, it isconsidered as a component. Some variable speed power driveproducts fall into this category, e.g. basic drive module (BDM).These are meant to be assembled by a professional assembler

Components w ith direct function

Component



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(e.g. panel builder or system manufacturer) into a cabinetnot in the scope of delivery of the manufacturer of the BDM.According to the EMC Directive, the requirement for the

BDM supplier is instructions for installation and use.

According to the EMC Directive the system manufactureror panel builder is resonsible for CE-mark, Declaration ofConformity and Technical Construct ion File.

Components with no direct function are not consideredas apparatus within the meaning of the EMC Directive.The EMC Directive does not apply to these. Thesecomponents include resistors, cables, terminal blocks, etc.

A finished product containing electrical and/or electroniccomponents and intended to be placed on the market and/ or taken into service as a single commercial unit.

Several items of apparatus combined to fulfil a specificobjective and intended to be placed on the market as asingle functional unit.

A combination of items of apparatus, equipment and/orcomponents put together at a given place to fulfil a specificobjective but not intended to be placed on the market as

a single functional unit.

Components w ithout direct function

Apparatus

Installation

Systems


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Chapter 4 - Purchasing dec isions for PDSs

What you need to know and do

Starting on page 20, we offer a step-by-step guiderelating to your purchasing requirements for PowerDrive Systems.

Before turning to page 20, you need to know the followingIEC terms for PDSs and their component parts, which maybe unfamiliar to many users.

KEY POINT:

TERMS THAT YOU MUST KNOW

1. Basic Drive Module (BDM) consists of the convertersection and the control circuits needed for torque orspeed. A BDM is the essential part of the Power DriveSystem taking electrical power from a 50 Hz constantfrequency supply and converting it into a variable formfor an electric motor.

2. Complete Drive Module (CDM) consists of the drivesystem without the motor and the sensors mechanicallycoupled to the motor shaft. The CDM also includes theBasic Drive Module (BDM) and a feeder section. Devices

such as an incoming phase-shift transformer for a 12-pulse drive are considered part of the CDM.

3. Power Drive System, or PDS, is a term usedthroughout this Technical Guide. A PDS includes thefrequency converter and feeding section (the CDM andBDM), motors, sensors, all cabling, filters, panels andany other components needed to make the PDS workeffectively.

Note: The load is not considered part of the PDS, butthe CDM can incorporate the supply sections andventilation.



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Now we strong ly advise you turn to p age 20, to discover the type of person you are.

Power Drive System (PDS)

CDM

(Complete Drive Module)

Feeder sectionField supplyAuxiliaries

Others

Motor & sensors

Driven equipmentor load

Installation or part of installation

HOW THE TERMS

FIT TOGETHER

BDM (Basic DriveModule)

Control sectionConverter section

S ystem contrS ystem contrS ystem contrS ystem contrS ystem control and sequencingol and sequencingol and sequencingol and sequencingol and sequencing


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22

WHO ARE YOU?IF THIS IS

YOU, TURN

NOW TO

PAGE.....

Machine Builder

is a person who buys either a PDS, CDM or BDM and

other mechanical or electrical component parts, such asa pump, and assembles these into a machine.

Note: A mach ine is defined as an assemb ly of linked parts or com ponents, at least one of which moves. It includes the appro priate actuators, contro l and power circuits joined together for a spec ific application, in particular for processing, treatment, moving or packaging of a material.

System Designer

carries out all the electrical design of the Power Drive

System, specifying all component parts which comprise

a PDS.

26

To make this Technical Guide easy to use, we havealso identified certain types of people who will beinvolved in the purchasing of drives.

Please identify the type nearest to your job function andturn to the relevant section.

End-User

is the final customer who will actually use the machine,

PDS or CDM/BDM.28

Panelbuilderconstructs enclosures into which a panelbuilder will

install a variety of components, including a CDM/BDM

and sometimes the motor. However, the built enclosure

does not constitute a machine.

30



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End-User - page 28

Drive Manufacturer

Panelbuilder -p.30

Distributor -p.32

System Des

Documents

AC DRIVESTechnical guide book.pdf