Embed Size (px)
Citation preview
The guide ofMarine Frequency Converters
marineEQUIPMENT
2
3
1 INTRODUCTION 4
2 TECHNICAL DESCRIPTION FORMARINE FREQUENCY CONVERTERS 5
Siemens Marine frequency converters 5
AC motors controlled by Marine frequency converters 5
Overview of the Marine frequency converter operation 6
The Marine frequency converter's load on the power supply 7
3 APPLICATIONS WITH MARINE FREQUENCY CONVERTERS 7
Marine frequency converter used in diesel-electric propulsion 7
Booster 9
Cargo pumps 9
Winches 11
Thrusters 12
Fans and cooling systems 13
Other applications 14
4 OTHER ISSUES 15
Energy saving 15
Pump characteristic with throttle valve control 15
Pump characteristic with speed control 15
Electromagnetic compatibility (EMC) 16
Harmonic currents and tuned filter circuits 17
Harmonic distortion of mains supply 17
Marine frequency with three possibilitiesfor Bus communication 18
Communication with PROFIBUS 18
Communication between drives by Siemens DRIVE-CLiQ 18
Commissioning and service with a Personal computer 19
Dynamic load limitation (DLL) 19
SUMMARY 20
Table of contents
4
The shipping industry is facing ever greater challenges,
especially regarding energy saving and the environment.
Lurking in the background are political shadows like
CO2 duties and dire predictions concerning the cost of
fuel in ten years time.
Authorities and owners are consequently focusing more
and more on shipping concepts involving less environ-
mental risk and energy saving.
Shipping installations having higher fuel efficiency in
all operational stages will be increasingly favored and
will presumably have great potential for future growth.
Additionally, the requirements of reliability, redundancy,
maneuverability and concerning long maintenance
intervals and short service response time are gradually
becoming stricter. Parts of these requirements can easily
be met by controlling the speed of electric motors.
In this guide, you will get a brief introduction to the
operational principle of a frequency converter, its
construction and application. When connected to a
frequency converter, an AC motor exhibits unique
properties in providing rotational speeds from standstill
to values in excess of the rated speed, and also in
maintaining exact torque control.
The Marine frequency converter system represents
a new concept due to its uniform power range.
The regulation and control properties of Marine
frequency converters enable the use of the same type
of frequency converters with all drives on board. Even
hydraulically operated equipment may advantageously
be replaced by Marine frequency converters and electric
motors.
Introduction1
This brochure will guide you through the majority of
applications of Marine frequency converters on board
a ship, pointing out the advantages of using them. It
will present to you the properties of Marine frequency
converters in given applications and suggest the cor-
responding solutions. At the same time, we will present
the possibility of integrating Marine frequency con-
verters in automation systems.
Any frequency converter will by nature create distortions
in the supply voltage and can thereby cause disturbances
to other on-board equipment. We will present how to
avoid such disturbances by the selective use of Marine
frequency converter configurations and show the
potential for improvements.
Siemens Marine frequency convertersFrequency converter requirements vary with respect tofunctions, the required survey and the uniformity of controlthroughout the power range. The frequency convertershould also be connectable to all system supply voltages.The new Marine frequency converter family from Siemenshas been developed for the ship industry market and com-plies with all the associated requirements.
The Marine frequency converters can also be deliveredwith rectifiers drawing a pure sine-shaped current, therebyreducing total harmonic distortion to less than 1%.
All frequency converters in the Marine design have thefollowing properties:
• Frequency conversion using IGBT technology• Uniform control philosophy• Same type of control panel• Identical electronic solutions and basic functions• Identical connection of control functions• Identical commissioning technique• Open software for customized applications
A function (a parametric number) given in one unit has theidentical meaning in all other units found in the range. Thesame applies to the function of the signal terminals andtheir allocation. The same also applies to functions likediagnostic memory, trace and reaction to faults. All unitsreact in the same way to control commands. This is animportant advantage to you as user: if you know how touse one Marine converter, you know how to use them all.
Marine frequency converters from Siemens is the firstfrequency converter system on the market covering all kindof applications with the same frequency converter philo-sophy. Here, the smallest units may be used for drivingpumps and fans, while the larger units may drive transversethrusters and motors for main propulsion. You will dealwith only one concept with respect to operation and main-tenance.
AC motors controlled byMarine frequency convertersFrequency converters using Pulse Width Modulation (PWM)inverter units provide the most favorable technical andeconomical solution for controlling AC motors. New IGBTtransistor technology components favor AC motor drives.Highly integrated microelectronic components havingpowerful calculation capabilities and nearly unlimitedstorage possibilities make it possible to realize large andcomplex functions at low cost with small space require-ments.
The speed-controlled AC motor has been a major innovationin all branches of industry, and the rapid rate of innovationwill cause a further increase in the need for such drivesystems.
The quality of a speed-controlled drive depends on the ac-curacy and the dynamic ability of the power exertion (thetorque) to be transferred to the driven machine and alsoon how precisely the speed regulation can be controlled.Additionally, it is extremely important to achieve optimumefficiency and to minimize power consumption.
Today, it is almost unthinkable to drive modern machinerywithout speed-controlled drives. Economical as well astechnical conditions must be evaluated when investing innew motor drive technology.
Disregarding the efficiency of the motor and the frequencyconverter, the load on the primary power source is theactive power required by the working machinery at anytime only. This will be the case even when the motoroperates in the partially loaded area, i.e. with unity powerfactor against the mains.
The onboard generators are not loaded with reactivepower and do not need be dimensioned for this. The figurebelow shows the typical efficiency factor of a motor anda frequency converter throughout the speed range witha constant load torque at all speeds. Marine frequencyconverters use optimum Pulse Width Modulation (PWM)causing the connected motors to maintain a high efficiencyand high torque utilization over the complete speed range.
2Technical Descriptionfor Marine frequency
converters
Marine frequency converter
The efficiency curve throughout the speed rangefor a Marine frequency converter controlled motor
Speed n/nrated [%]
100
90
80
70
60
00 40 60 80 100
Motor
Converter
Total
5
6
Large drives such as diesel-electric propulsion systemsnormally get their electrical power from three or morediesel engines. Here is a great potential for energy savingin using only the number of diesel engines needed for thedesired propulsion and the other energy needs on board.Auxiliary diesel engines will no longer be needed and theplanning of maintenance becomes easier.
A diesel-electric propulsion system enables a more flexibleand optimal positioning of the heavy and bulky compo-nents and will at the same time reduce the total requirementfor area and space. Simultaneously, improved system plann-ing will result in reduced service costs.
Cooling water pumps and fans also represent a greatenergy saving potential since they are dimensioned ac-cording to classification requirements with respect totemperatures. The result is the use of excessive energy inpumping unnecessary volumes of air and water throughthe system. For much of the year, air and water temperaturesare normally considerably lower than the criteria used asthe basis for the classification requirements. Investment inMarine frequency converters with integrated temperatureregulation will soon pay for itself.
For other uses such as winches, thrusters, dischargingpumps, etc., a Marine frequency converter-fed AC motorwill exhibit better operational features than hydraulics.
A Marine frequency converter will regulate the speed ac-curately and make the motor yield an exact pre-set torque.The rugged squirrel cage motor may be controlled to givea uniform torque from standstill to well beyond the ratedspeed.
Speed-controlled motor drives have the followingadvantages:
• Lower investments• Energy saving in the partial load range• Low maintenance costs as wear of machinery and
materials are saved by the controlled motor operation• Less space in relation to hydraulic or diesel solutions
Technically better process solutions:
• Improved operation reliability• Less wear, less maintenance• Simple monitoring and operation• Fast and safe fault diagnosis• Economically friendly operation
Diesel-electric propulsion of a luxury yacht
Overview of the Marine frequency converteroperationThe task of the frequency converter is to convert the fixedfrequency and voltage of the power supply (mains supply)to a variable frequency and voltage for feeding the motor.The speed of the motor will change linearly with thefrequency. In order to exert an exact control of the motortorque, it is important to keep the ratio of voltage andfrequency constant throughout the speed range of themotor, i.e. V/f ~ = constant; is the magnetization fluxof the motor.
The rectifier of the Marine frequency converter convertsthe AC supply voltage to a constant DC voltage, and thetask of the AC inverter is to transform this DC voltage intoa variable AC voltage. The Marine frequency converterperforms this energy conversion in an almost loss-free way.The efficiency of the Marine frequency converters lies inthe range of 97–98 %. The power rectifier, consisting ofdiodes or thyristors, does this in a way to ensure that thecurrent drawn from the supply is in phase with the supplyvoltage, i.e. the Marine frequency converter will only drawactive power from the supply, i.e. almost unity power factor,and there is no need for reactive power. Ignoring theefficiency factor of the motor and the Marine frequencyconverter, the motor drive will only draw the active powerat any time needed by the driven load. This also applieswhen the motor operates in the partial load range.
The high efficiency of a speed-controlled squirrel cagemotor throughout the speed range is superior comparedwith other forms of drives.
The construction of a pulse width modulated Marine frequency converterwith power rectifier, intermediate circuit and AC converter
M~
3AC 208 - 690 V
50/60 Hz
3AC 0 - Vrated
Rectifier
DC link
Inverter
V
t
V
t
V
t
Power and current load on the mains and motor when operatinga constant torque loaded motor through its speed range
The Marine frequency converter'sload on the power supplyThe figure below shows the principle of a Marine frequencyconverter controlled motor drive. The two graphs show thecurrent, voltage and power supplied to the motor or drivenmachine and corresponding conditions on the supply sideas a function of the motor speed. The condition here is thatthe driven machine requires a constant torque T over thespeed range.
The physical relation between torque T and power P is
T [Nm] = 9.55 . P [W] / n [rpm]
We see from this that the output power P will increaselinearly with the motor speed n when keeping the torqueconstant. Because the control system of the Marine fre-quency converter ensures that the motor operates withconstant magnetization , the motor current will be directlyproportional to the torque T, i.e. I [A] .~ k . [Nm]. Thecondition for a constant magnetization is that the appliedvoltage V increases proportionally to the frequency f, i.e.V/f = constant = . The basic physical law stating that P isthe product of voltage V and current I, i.e. P = V . I is evidentfrom the diagrams.
Noting how the physical factors on the supply side of theconverter changes as a function of the rotational speedwhen keeping the torque of the working machine constant,the absorbed power Pi from the power source must neces-sarily be identical with the output power of the motor Powhen ignoring the efficiency.
As the power voltage V is constant and the physical conditionP = V . I must be met, the current I, which the Marinefrequency converter draws from the power supply, willincrease proportionally to the motor speed, even when themotor current I and the torque remain constant. These twocurrents will be identical only at the rated motor speed.From the given physical conditions, the current load willbe very low at low speeds or at low loads. Starting a motordirectly from the power source, the motor current will be6–7 times the rated current. When using a Marine frequencyconverter, the source current will be only a fraction of therated motor current. This means that the mains voltagedrop caused by a Marine frequency converter-controlledmotor, small or large, is negligible.
3Applications withMarine frequency
converters
Marine frequency converterused in diesel-electric propulsionFor most types of vessels, a diesel-electric propulsion systemis superior to a conventional diesel system with respect totechnical, operational and economical aspects.
The five most important aspects making a diesel-electricpropulsion system attractive are:
• Reduced maintenance work• Increased reliability• Better maneuverability• Improved environment• Considerable saving in energy
A diesel-electric propulsion system is normally equippedwith two propellers and three or more generators, givinghigh availability. One or four propeller systems are also notuncommon depending on the type of vessel (e.g. for largeferries).
A system of four diesel engines will normally be the mostflexible system. The number of engines simultaneouslyin use will depend on the desired thrust and the speed ofthe propellers. This implies that the number of engines inoperation will be restricted to the actual number neededfor restoring the energy balance. The highest availabilitywill be achieved when three diesel engines are in operationand the vessel can still maintain 90 % of its maximum speed.With a system of this kind, an auxiliary diesel engine issuperfluous. This means that planned maintenance maybe performed without jeopardizing system reliability.
In large propulsion systems where Marine frequency con-verters use a three-winding front transformer, a specialfront feeding system is used for charging the DC link circuitof the Marine frequency converter.
When using the Active Front End (AFE) as the feedingsystem, an input transformer is not applicable in casethe line voltage is equal to the input voltage of the drivesystem. With this system, the harmonic distortion isnot only extremely low (less than 1 %) but a power factorcompensation of the power line is also possible.
Machine room with electrical motors – each 3 MW
Motor side
Feeder side
M~
3AC 208 - 690 V50/60 Hz
3AC 0 - Vrated
nrated n [rpm]
Rectifier
DC link
Inverter
IPV
VPTI
Voltage VPower PTorque TCurrent I
Current IPower PVoltage V
nrated n [rpm]
Advantages of diesel-electric propulsion systems
Economically favorable
• Optimal fuel consumption of the diesel enginefor generating electricity
• Less sooting due to optimum operation with respectto rotational speed and load range
• High efficiency factor throughout the speed range
• Reduced maintenance cost due to increased serviceintervals caused by optimum operation time of the dieselengines
• Better conditions of maintenance planning
• Minimum downtime for maintenance and service
• Flexible use of generators
Operational reliability
• Modular construction and redundant systems witha minimum of possibilities for total loss of propulsion
• Radical reduction of moving mechanical parts
• Experience through more decades with the used electricalcomponents
• MTBF (Mean time between failure) is vastly improved using a diesel-electric system with fixed propeller insteadof a conventional system with controllable pitch propeller
Flexibility
The modular construction of a diesel-electric propulsionsystem permits a flexible placement of onboard units:
• No long propeller shafts
• More practical location of diesel engines
• Reduced space and area requirements
• Flexibility in the choice of diesel engine speed
• Easier to make a sectioned engine room
Propulsion room with one 736 kW motor for bow thrusterand one 900 kW motor for a retractable azimuth propeller
In conventional propulsion with variable diesel enginevelocity, the specific fuel consumption varies with the speedof the engine (see figure on page 5). This can often befound in smaller ships, in which the velocity of the ship isnot controlled by a pitch shift propeller but by the velocityof the engine. There is a point of optimum fuel consumptionfor one certain speed, which in this form of propulsion isnot reached very often, as it relates to only one fixed velocityof the ship.
Now using a variable speed drive with diesel-electric pro-pulsion, the speed of the boat is neither regulated by thepitch shift propeller nor by the variation of the diesel enginevelocity, but by the Marine frequency converter and theelectric motor.
Therefore, the main power plant of the ship, the dieselengine, can always run at the point of optimum fuel con-sumption.
The effect:Less sooting of the diesel engine, thereby less maintenance.Smaller, high-speed diesel engines that have lower prices.Lower fuel consumption.In total: lower costs.
8
A diesel-electric propulsion system with generatorsand two propulsion propellers
Fuel consumption in relation with speed
M~
M~
~ ~~ ~
G~
G~
G~
G~
Diesel engine
Generator
Mainswitchboard
Transformer
Marine frequencyconverter
Inductionmotor
Speed [rpm]
Power [kW]
Torque [Nm]
Specific fuel consumption [g/kWh]
0 3000 40001000 2000 5000 6000
9
Marine frequency converters for boosterBooster drives increase the main power propulsion ofvessels by using an electric motor in combination with themain engine.
They support the ship's diesel engine when accelerating,relieve it over the complete speed range, guarantee con-sistently high speeds and improve its efficiency.
In the diagram below, you will find an overview of a boosterdrive system implemented in an electrical system.
Example of a booster drive system with 3 auxiliary generators
The Booster drive can operate in conditions such as:
• Main engine is out of order. This means that the propellerof the vessel is controlled over the Booster drive.
• In case the vessel is at crawl speed, the main engine canbe switched off and propulsion power is delivered by theBooster drive.
• When the main engine is running at nominal power andthe speed has to be increased.
Highlights for this device are:
• Main engine and main generator can be smaller due to the fact that additional propulsion power can be suppliedby the booster. Also the auxiliary generators will be usedmore optimally.
• Lower energy consumption especially in partial loads. Also fuel saving by switching off the main engine atcrawl speed.
• Less maintenance due to the fact that auxiliary engines are running at optimal condition and main engine is notused at low speed where low power is applicable.
Marine frequency convertersfor cargo pumpsIn connection with transport of goods, we need equipmentfor loading and unloading ships.
These are for example pump drives for oil tankers, chemicaltankers or edible-oil tankers.
As the Marine frequency converter system is of a modularconstruction, it is possible to customize pump conceptsaccording to the number of pumps, their sizes and theirsimultaneity factor. The pump drives with associated elec-trical motors are either located in a pump room or long-axled pumps are used with their motors placed on deck.
For on-deck location, the motors must have a degree ofIP56 – heavy sea protection – and must often have anexplosion-proof design. Speed-controlled pump drives usingMarine frequency converters provide much better flexibility,efficiency and noise level than hydraulically-driven pumps.
Also pump-related special “Technology software” can bepart of this solution for protection of the pump and a higherproductivity of the total pump system.
Marine frequency converters offer both speed and torquecontrol and with AC motors of high thermal reserve, supremeflexibility can be achieved in a pump system of this kind.
The figure shows the high torque obtained with SiemensAC motors used in conjunction with Marine frequency con-verters, even above the rated motor speed.
Typical torque utilization characteristicfor a self-cooled squirrel-cage motor as a function of speed
AC-connected systems
Input power to the Marine frequency converter feeding thecargo pumps comes from a circuit breaker via the maindistribution board. Each cargo pump has its own Marinefrequency converter and is individually controlled. TheMarine frequency converters communicate with the auto-mation system via conventional I/O signals or via serialcommunication channels, for instance PROFIBUS, Ethernet,and CAN-Bus.
The Marine frequency converter may form part of the mainswitchboard or be mounted in separate cubicles or cabinetsystems.
Cargo pumps with AC-connected system
M~
~~
G~
G~
G~
G~
Diesel engine
Generator
Mainswitchboard
Propulsion
Booster
M~
M~
M~
M~
M~
M~
M~
M~
~ ~ ~~~ ~ ~~~ ~ ~~ ~ ~ ~~
AC Busbar
Main switchboard3AC 380 / 690 V, 50/60 Hz
TorqueT/Trated [%]
Utilizationaccording totemperature class F
Utilizationaccording totemperature class B
Constant fluxrange
Field weakeningrange
Frequency [Hz]
100
90
80
70
60
706050403020100
10
DC-connected system
Especially where pumps are not to be simultaneouslyoperated, it may be practical to allow the Marine frequencyconverters to be fed from the main switchboard via tworectifiers or Active Front End. The rectifiers or Active FrontEnd in turn feed each converter via a DC busbar. The di-mensioning of the rectifiers should be based on the simul-taneity factor of the pumps, and not on the totally installedpumping power. The advantage of such a system is thatthe total dimensions of the main switchboard including theMarine frequency converters are optimized.
Cargo pumps with DC-connected system
AC-connected low-voltage drives in cross connection
One Marine frequency converter is feeding a combinationof cargo pumps but is controlled individually. The powerof the Marine frequency converter depends on the powerof the pumps, the amount of pumps which can be inoperation and if it is necessary to start a pump on a runningconverter. It is also possible for example to control twodifferent types of motor power ratings on one Marinefrequency converter by means of selection in the Marinefrequency converter.
All contactors (output and interconnection) and pump-related “Technology software” are controlled by the Marinefrequency converter itself by using the PLC and processfunctionality inside the low voltage drive system. Further-more, a connection to the automation system is possible.
For maximum availability of the pump drive system, anemergency control is available in front of the low voltagedrive cubicle. With this solution, an unloading of the tanksis still possible in case the overall automation system is outof order.
Block diagram of a pump drive system by means of cross connection
Cabinet of cargo pump
An interconnection between each low voltage drive systemis also available for maximum availability of the pumpsystem. In case a Marine frequency converter is out of order,an interconnection can be made to the other one to ensurethat the tanks can be unloaded. Thereby you guaranteemaximum availability of the pump system.
All contactors (output and interconnection) and pump-related “Technology software” are controlled by the Marinefrequency converter itself by using the PLC and processfunctionality inside the low voltage drive system anda connection to the automation system is also possible.
M~
M~
M~
M~
M~
M~
M~
M~
~ ~==
= = = = = = = =~ ~ ~~ ~ ~ ~~
DC Busbar
Main switchboard3AC 380 / 690 V, 50/60 Hz
M~
M~
M~
M~
~~
~~
Main switchboard3AC 380 / 690 V, 50/60 Hz
11
AC-connected system in matrix connection
The output of each low-voltage drive Marine frequencyconverter is connected to a contactor matrix.
All low-voltage drive converters are controlled overPROFIBUS by a SIMATIC PLC system which controls:
• The contactors in the matrix by distributed I/O modules.
• On the touch-screen mounted in front of the converter drive system information on the status of the system aswell as an emerging mode can be selected.
• Interface connection to the overall automation system (for example cargo computer) by I/O signals or of a serialcommunication link, for instance PROFIBUS, CAN-Bus andEthernet.
• Interface connection by I/O or serial communicationwith operator panel.
• Interface connection by serial communication withtouch panel.
• Faster diagnosis, shorter downtime, reduced maintenancecost by using remote access.
• Easy upgrading or adding of supplementary services.
The matrix combination provides maximum flexibility andavailability.
Block diagram of a pump drive system by means of a matrix connection
Marine frequency converters for winchesWindlasses, mooring winches, etc. have until now mostlybeen equipped with hydraulic or pole changing motor drivesystems.
Winches using squirrel cage motors and Marine frequencyconverters have improved operational features and a sim-plified total concept. The robust squirrel cage motor providesa standstill torque twice the rated torque, and at the sametime, the maximum speed of rotation is 2 to 4 times therated value. Winch drives using Marine frequency converterswill exhibit improved control and optional features usingMarine frequency converters with Vector Control since theexact control of speed and torque from n = 0 throughoutthe total speed range is guaranteed.
For most winches, the Marine frequency converter will beequipped with the technology board fitted with an appli-cation-oriented software. Among other things, the techn-ology board takes care of all the superior speed and torquecontrol as well as of the control of the holding brakes. Italso continuously supervises the brake momentum versusthe desired rotational speed.
M~
M~
M~
M~
M~
M~
~~
~~
~~
Operator desk
Touch panel
Remote access
Main switchboard
3AC 380 / 690 V, 50/60 Hz
Interface connectionI/O or serial
communication
12
Principal sketch of a winch control (Winch)
With Marine frequency converters, electrical braking canbe performed as follows:
• The electrical braking energy is fed back to the mains. The precondition is that the mains is able to receive thesuperfluous electrical energy, i.e. other heavy loads mustbe connected.
• The electrical braking energy is absorbed by a brake resistor. With braking of long duration, this will lead to a lot of heat being dissipated from the resistor, requiringmore space than the previous braking option.
Comparison between features of hydraulic drives and Marinefrequency converter controlled motor by winch application
Windlasses on a Hopper dredger 300 kW
In conjunction with Marine frequency converters, the con-trollability requirements for winches are analogous to thosefor cranes, be it grab cranes or container cranes. On a crane,there are often many motor drives, like for instance for themain hoist, an auxiliary hoist, gantry movements andtransverse movements.
Considering power load and the simultaneity factors, themost compact configuration of the Marine frequency con-verter system would be to use a common mains rectifierfeeding all converters via a DC busbar. The rectifier maywell be of the feedback-of brake-energy type or with a com-mon brake chopper mounted on the DC busbar. The DCbusbar will then work as an energy smoothing connection.
Marine frequency converters for thrustersBow Thrusters have until now mostly been equipped withhydraulic systems.
This hydraulic system contains a fixed speed motor drivingthe thruster with a fixed speed, the water flow itself iscontrolled by changing the pitch of the propeller throughthe hydraulic system.
With the Marine frequency converters, the speed of thethruster can be changed in a wide range where the pitchis fixed. In other words, the water flow by the thruster iscontrolled by the speed of the motor. The complete controlof the thruster is part of the Marine frequency converter.
For the steer able thruster, the Marine frequency converteris also an optimal solution.
Both movements (rotating and speed control of the thrus-ters) can be controlled by the drive.
LV Switchgear
Frequency converter
Electric motors
Winch
Winchinterface
Motorinterface
EmergencyStop
Windlasscontrol system
PROFIBUS
Warp speed [%]
Hydraulic drive
Electric drive
200
150
100
50
0
Torque [%]160100500
13
Marine frequency converters in fansand cooling systemsOn board most ships, there are a great number of pumpsserving multiple purposes. Cooling water pumps are es-pecially dimensioned to have their rated capacity at a watertemperature of 32 °C or 38 °C. When operating in coolerseas, this means that unnecessary high volumes of coolingwater are pumped through the systems, resulting in highcost of energy and wear of the mechanical equipment.
Vessels used for instance for transporting fruit require verystable temperatures. In passing through climatic zones withchanging temperature conditions, a Marine frequencyconverter controlled cooling system will ensure constantstorage room temperature.
On board passenger and cruise vessels, considerable energyis used for ventilation and air conditioning. Day cycles andchanging environmental temperatures mean the motorpower requirement for systems of this kind will undergolarge variations.
With temperature control, only the required motor powerwill be used to maintain the desired temperature.
For supply vessels, the ballast pumps, cargo pumps for fuel,brine and mud, etc. are installed with speed regulationusing Marine frequency converters.
The use of Marine frequency converters in regulating engineroom temperature has also proved to provide great savingsin energy.
Most pump and fan systems pay for themselves within acouple of months of operation through energy saving. Theoperational advantages of reduced wear and maintenancecome in addition to this.
The first figure above shows the principal conditions in atemperature-controlled pump. The temperature behind thepump is measured using a transducer giving a 4–20 mAoutput signal. The Marine frequency converters have inte-grated PID regulators which may be used for controllingtemperature, volume, pressure levels, etc. In the givenfigure, the desired temperature is entered as a 0–10 V,0–20 mA or 4–20 mA signal. The Marine frequency con-verter controller will cause the AC motor to rotate at thespeed needed to achieve the desired temperature.
Supply vessel converter drives for cargo pumps,seawater cooling pumps and ventilation on board
For two or more pumps or compressors working in parallel,only one machine will actually have to be speed-controlledwhereas the others may be directly engaged or disengagedfrom the mains. In such cases, the Marine frequency con-verters are equipped with application software.
This software completely controls and supervises boththe Marine frequency converters and the pumps operateddirectly from the mains. When the Marine frequency con-verter operates its controlled motor at maximum speedand there is a need for a still higher volume or pressure,the Marine frequency converter will switch the next motordirectly on line. The Marine frequency converter will nowautomatically reduce the speed of its controlled motorduring the acceleration process of the directly engagedmotor, thus preventing pressure jolts and oscillations in thepiping system.
Temperature regulation of a pump with Marine frequency converter
Pump control with Marine frequency converter, pumps workingin parallel with only one speed-controlled machine
M~
~~
Requiredtemperature4 - 20 mA
PID
Temperaturesignal4 - 20 mA
M~
M~
~~
Requiredpressure4 - 20 mA
Measuredpressure4 - 20 mA
PID
14
Marine frequency convertersfor other applicationsThe Marine frequency converter drives can also be usedfor other applications such as cranes and conveyor belts.
Especially where speed or torque-controlled drives arenecessary, the marine drives are at their best.
With the open software functionality, customizedapplications can be easily adapted in the Marine frequencyconverter by using this open software.
Principal sketch of a Marine frequency converter for a crane
M~
M~
M~
M~
M~
M~
M~
~=
=~
=~
=~
=~
DC Busbar
Mainlift
Brakingchopper
PortalSwing
Main switchboard
3AC 380 / 690 V, 50/60 Hz
15
4Other Issues
Energy savingWithin the ship industry, fuel consumption is an importantpart of operational costs. Especially when oil prices arerising, the fuel consumption of the vessel will get a moreimportant priority within these costs.
Energy saving is then an attractive way to reduce the fuelcosts of a vessel.
With Siemens Marine frequency converters, a substantialamount of energy can be saved, especially in partial loadsat pumps and fans.
Shown below is a comparison between pump operationwith throttle valve control and with variable speed control.
Pump characteristic with throttle valve control
The pump can deliver the amount of energy E given by thepump characteristic (blue) while the plant (i.e. cooling orheating circuit) needs only the energy shown by the plantcharacteristic (red).
The energy difference (red arrows) has to be “throttledaway” = wasted.
The energy consumption at the input is approx. the same,throttle valve means mechanical control at the output.
LegendBlue: pump characteristic Red arrows: energy “throttled away”Red: process characteristic Black: power consumption
The following graph shows the pump characteristic (blue)and the various regimes of the plant/process (red), regimesachieved using the throttle valve control.
The energy waste is materialized by the pump headdifference which is not used.
Example: necessary flow 200 m3/h:necessary Q = 200 m3/h at 50 m (equiv. potential energy),but the pump can give 200 m3/h at 210 m (equiv. potentialenergy), results210 – 50 = 160 m wasted pump head, in other wordsthis means 160 m wasted equiv. potential energy (see graphright above).
Throttle valve control along pump characteristic (blue)
Pump characteristic with speed control
The pump can – due to variable speed n which meansvariable/controlled flow Q – deliver the amount of energyE which is in every moment necessary in the process/plant.No energy difference has to be wasted. The energy con-sumption E at the input follows the speed control, i.e. itdecreases with the speed reduction. Speed control meanselectrical control at the input.
LegendBlue: pump characteristicRed: process characteristicBlack below: power consumption at various speeds
Energy E / Pump head H
Power P Flow Q
Flow QQmaxQmin
n = nA
n = nA
QA
Pump head H [m]
350
300
250
200
150
100
50
0400200 300 6005000 100
Flow Q [m3/h]Operation point Q = 400 m3/h at 150 m
Qmax = 450 m3/h
Available power in operation point
*) To despense (“throttle away“) 210 - 50 = 160 m!
*)
Energy E / Pump head H
Power P
Flow Q
Flow Q
Qmax
n = nA
n1 < nA
n2 < n1
n3 < n2
n4 < n3
n
QA
16
Speed control: along plant/process characteristic (red)
Siemens Marine can support you with the calculation ofthe amount of energy saved – see graph below:
The shaded area represents the energy saved due to thevariable speed i.e. speed control
Black: energy consumption with throttle valve controlRed: energy consumption with speed control
The same effect will be with application with a constanttorque characteristic such as reciprocal compressors.
Electromagnetic compatibility (EMC)The electromagnetic compatibility according to the definitionof the EMC directive defines “the capability of a device tooperate satisfactorily in an electromagnetic environmentwithout itself causing electromagnetic interferences whichwould be unacceptable for other electrical devices in thisenvironment”.
In order to ensure that the relevant EMC standards arecomplied with, interference emissions must be limited tocompatible values on the one hand, and the devices mustachieve a sufficient level of immunity on the other hand.
Marine frequency converters are producing electromagneticemissions in their power sections by switching on and offhigh electrical voltage very fast. This creates emissionswhich are conducted to the environment by the connectedpower cables and radiated to the environment by air. Theseemissions must be limited.
The controller and other electronic components of Marinefrequency converters consist of very sensitive electronicdevices which must be protected against electromagneticinterference.
To limit the interference emissions of Marine frequencyconverters, the following measures have to be taken:
• Interference suppression filters to limit conductedemissions.The Marine frequency converters are equipped with filtercomponents to reduce the conducted emissions accordingto the standard EN 61800-3 for Industrial Environment and in accordance with the specifications of the ship classification societies like DNV, GL, LR, ABS and BV.
• Shielded motor cables to reduce radiated emissions.This precaution has to be taken when installing the drivesystem.
• Compliance with the installation guidelines.This part is delivered together with the operating instruc-tions of a Marine frequency converter.
To ensure the immunity of Marine frequency converters,the following measures have to be taken:
• Shielded signal cables to protect the wires connected tothe controller against electromagnetic interference.This precaution has to be taken when installing the drivesystem.
• Compliance with the installation guidelines.This part is delivered together with the operating instruc-tions of a Marine frequency converter.
When all these measures are taken, the Marine convertersare operating reliably without interfering with other equip-ment in the same environment.
Pump head H [m]
n
250
200
150
100
50
0400200 300 6005000 100
Flow Q [m3/h]
Electrical power Pel [kW]
300
250
200
150
100
50
0400200 300 6005000 100
Flow Q [m3/h]Operation point Q = 400 m3/h at 150 mQmax = 450 m3/hAvailable power in operation point
17
The filter circuits may be connected directly to the low voltageside to keep higher harmonic currents away from the mainsnetwork. The filter circuits consist of capacitors in series witha coil (inductor). The resonance circuits are tuned to giveapproximately zero resistance to each of the harmonic com-ponents. Thus, the major parts of the harmonic currents areabsorbed by the filter circuits. Only tiny parts of the unwantedcurrents will return to the mains network, causing only anegligible distortion of the mains voltage.
As seen from the mains (50 Hz or 60 Hz), the filter will appearas a capacitive impedance. This means that the filter circuitswill not only absorb the harmonics but also conduct capacitivecurrents. They will therefore additionally act as reactivecompensation for the complete network. With filter circuits,the harmonic currents may be reduced to a maximum ofup to 90 %. Sensitive equipment of other types may not beconnected to the network unless separated by a transformer.
Absorption of harmonic currents in filter circuits
As seen from the figure, the capacitance and inductanceplay crucial parts in the reduction of harmonics. This meansthat to avoid resonance, the inductivity of the network isimportant in the dimensioning of the filter circuits. Thenumber of generators in operation will change the networkinductivity, i.e. the short-circuit reactance of the networkand the filter circuits must be dimensioned to cater for suchoperational situations as well.
Harmonic distortion of mains supplyAll mains rectifiers used in DC and AC motor drives equippedwith diodes and thyristors have the characteristic of draw-ing non-sinusoidal current form the mains. Consumptionof this kind will thereby distort the mains voltage. Thedegree of distortion is known as the Distortion Factor (DF)The classification companies often require that THD (TotalHarmonic Distortion) must be less than 5%, which mustbe taken into account when choosing a drive concept.
The higher the total Marine frequency converter power isrelative to the generator power and its short-circuit power,the higher the distortion of the mains voltage. A networkwith high voltage distortion might damage other networkcomponents and lead to unexplainable fall-outs.
Marine frequency converters for small and medium poweroutputs are designed with so called 6-pulse mains rectifiers,i.e. with 6 diodes or thyristors used in the rectifier. Thefigure gives the current drain from a generator supply ofa 6-pulse frequency converter, and also shows how thisdistorts the mains voltage. If such concepts are used forlarge consumers, the main source distortion may amountto something like 20 to 30%.
M~
~~
Medium voltage network
Low voltage network
Transformer
Tuned filter circuit
Decomposition of the rectifier current into basicand harmonic components
Uphase
0
IL
I(1)I(5) I(7)
Harmonic currents and tuned filter circuitsAll power electronic units where diodes and thyristors areused will cause distortion of the mains voltage. Thyristorrectifiers will in addition cause considerable inductivereactive currents.
The rectifier current consists of a multitude of sine-shapedcurrents, a basic frequency component and a lot of harmoniccurrents of frequencies several times that of the mainsfrequency.
The network impedance will cause all these currents togenerate voltages superimposed on the fundamental sinu-soidal wave form of the mains. This leads to distortion ofthe mains voltage which may give rise to mains faults andfall-out of other subscribers.
The mains rectifier loads the network with the basic fre-quency I1 and returns to the network (power line) currentswith harmonic numbers v
v = 6 . k –+1, k = 1, 2, 3, ...
For higher motor powers (as seen in relation to the generatorcapacity), the Marine frequency converters should beconstructed with a 12-pulse rectifier, i.e. 2 times 6-pulsemains rectifiers connected to a separate supply systemvia a three-winding transformer. The transformer output(Dy5Dd0) group is arranged to give a 30° electrical phaseshift between the two secondary winding systems.
The connection to the pre-connected mains circuit will inthis case result in a reduction of the mains voltage distortion.With two such Marine frequency converter drives, theconnection groups of the two transformers may be 15°phase shifted relative to each other. We have then obtaineda so-called 24-pulse connection to the mains; however, inorder to obtain the full reduction of the harmonic distortion,it is a condition that the two motor drive system are equallyloaded.
With their Marine frequency converters, Siemens is havinga complete type range of mains rectifiers using transistortechnology (IGBT). In construction, this rectifier is identicalto the frequency inverter. The advantage of transistors istheir ability to be turned on and off. The Marine ActiveFront End mains rectifiers are controlled in a way to drawan undistorted sine-shaped current from the mains.
This means that the power factor is exactly equal to 1.However, the Active Front End rectifier may be parameterizedif the power factor is required to deviate from 1. The valueof the power factor may be parameterized to be eithercapacitive or inductive. This means that Marine frequencyconverters with Active Front End mains rectifiers may takeover the task of the generator to supply reactive power toinductive loads like for instance motors directly connectedto the mains.
The voltage distortion from an Active Front End is below2%, which means that the distortion is not visible in theoscilloscope picture.
For vessels with an amount of large consumers relativeto the generator power at its maximum, the Active FrontEnd is the ideal solution. This is true both with respect toprice and space requirements, and the resulting low networkdistortion. The use of an Active Front End will make a cleanpower machine superfluous, e.g. a rotating or static con-verter.
The principal construction of Marine frequency convertersas 6-pulse, 12-pulse and as Active Front End with the associatednetwork current loads
Marine frequency with three possibilitiesfor Bus communicationThe digitalization of control and regulation facilities providespotentials for new possibilities. Marine frequency convertersmay be connected to automation systems via serial in-terfaces and data bus systems. Parameters from Marinefrequency converters may then be exchanged with thosefrom an automation system for process control (scale values,actual values, commands and messages), for process adap-tation (control set points, choice of curve characteristics)and for service cases (stored fault messages, times ofoperation, measured and calculated process parameters).The quality of the data interface, the structure and contentof parameters as well as the operational and service philo-sophy form parts of the essential quality properties of aspeed-controlled motor drive.
Communication with PROFIBUSMarine frequency converters may be connected to thePROFIBUS system standardized by DIN 19245. Other com-ponents are also available, like actuators, valves and sensorsconnectable to the PROFIBUS standardized bus system. Allinformation previously connected to the Marine frequencyconverter via the conventional I/O terminal block may nowbe transferred via the bus system on a two-wire cable.The automation system delivers its commands and scalevalues through the cable in the form of telegrams. Statusreports and actual values run in the opposite direction forpossible presentation on a screen-based control system.PROFIBUS guarantees a quick and safe data transmissionusing the Master-Slave principle. The high transmissionrate of 1.5 Mbit/sec and the short reaction time enablestransmission periods of less than 1 ms to and from theautomation system (the master) for instance connectedto a Marine frequency converter (a slave).
Communication between drivesby Siemens DRIVE-CLiQWhen operating cranes and winches where one motor driveis mutually dependent on the operation of other drives,much equipment and planning may be saved by letting themotor drives communicate directly with each other. Thisfast connection may convey information of changes in bothspeed and torque to the other motor drives. The signalingbetween drives is extremely fast due to the fact of theEthernet communication. This fast communication may bemade with or without PROFIBUS.
When PROFIBUS is used, non-time-critical information canbe handled over this communication net, the time-criticalinformation over the DRIVE-CLiQ bus. In this way, moretime-critical information can be handled.
M~
M~
M~
6-pulserectifier
12-pulserectifier
ActiveFront End
19
Commissioning and servicewith a Personal computerFor the Marine frequency converters powerful service toolsare available.
STARTER is a tailor-made visualization program for com-missioning and service, creating figures and text to aid yousafely through implementation. Having put the Marinefrequency converter into service, STARTER may be used foreasy adjustments of parameters and functions.
Having commissioned or made the necessary changes inparameters, the complete content of the Marine frequencyconverter parameter memory may be stored in a PC. Thiswill be a safe back-up and may come in useful when theday comes for replacing the Marine frequency converteror its control board. You will then only have to transfer thecomplete set of stored parameter data from the PC.
STARTER also has an oscilloscope function where up tosix physical values, for instance current, rotational speed,torque, etc. may be simultaneously measured on the PC.
Dynamic load limitation (DLL)Siemens philosophy is that a heavy load drive systemwith its generators, main switchboards, Marine frequencyconverters and motors is one system even with respect todynamic load changes.
Due to the largest consumers, it is of vital importance thatthis consumer is not able to overload the generator, orin a worst-case scenario, cause a black-out in the electricsystem. Such a large consumer with Marine frequencyconverters can be equipped with a dynamic load limitationsystem. This is a control system which continuously limitsthe power consumption of the heavy consumer drive ac-cording to the actual, available generator capacity.
In case of electric propulsion and the dynamic load limitationoption, the Marine frequency converters are also adaptedto the dynamic behavior of the propeller. The Marine fre-quency converters ensure that the power oscillation of thepropellers in heavy sea does not result in power oscillationsin the generators and on the main bus.
All these important characteristics of the Marine frequencyconverters and the dynamic load limitation system enablethe heavy consumer drive to act as a small consumer in theship's electric system.
Dynamic load limitation: Power reduction of the drivewhen available generator power is suddenly reduced by 50%
Load [%]
Load on generators
Drive output power
120
100
80
60
40
20
0100 150 2502000 50 350300
Time [ms]
The dynamic load limitation system will continuously adaptand limit the power consumption to the generators' maxi-mum load. Enabling the complete electric system, andparticularly the generators, to be run according to theirnominal loads, no other control system is needed to ensurethe reliability of the power supply on board. If one dieselgenerator has an unexpected sudden shutdown, theDLL system will immediately react. The power consumptionof the heavy consumer system will, within 160 ms, bereduced and kept within the nominal load limits for theremaining generators. The dynamic load limitation systemis so fast that a black-out is avoided. The dynamic loadlimitation system is an option in the Marine frequencyconverter and is independent of the Power ManagementSystem (PMS).
Royal Carribean International: “Radiance of the Seas“
w w w . s i e m e n s . c o m
Siemens AGAutomation and DrivesLarge Drives, Marine EquipmentPostfach 474390441 NÜRNBERGFEDERAL REPUBLIC OF GERMANYTel. +49 911 433 9516Fax +49 911 433 9751
The main customer benefits and important charac-teristics of the Marine frequency converter are:
• Easy to order, order specific documentation,fast logistics and worldwide service
• Universal operation, Engineering and Serviceof the equipment
• PROFIBUS Interface for easy implementationin higher-ranking automation systems
• Easy integration into existing installations,compact with small erection area needed
• Low noise level
• Standard and compact cabinet in IP22 and IP54in air and water cooling
• Easy commissioning, for standard applicationsonly few parameters have to be adjusted
• Easy operation through menu-guided control panelwith graphic-supported plain text display
• Excellent serviceability
• Special security concept for protection againstunintentional or unauthorized calibration changes
• Encoder-free Vector Control for robust and reliableoperation
The information provided in this brochurecontains merely general descriptions orcharacteristics of performance which in actualcase of use do not always apply as describedor which may change as a result of furtherdevelopment of the products. An obligationto provide the respective characteristics shallonly exist if expressly agreed in the terms ofcontract.
Summary
Order No.: 6ZB5731-0AB02-0BA0Printed in the Federal Republic of Germany18402/522275 Vog 1104 0.5
Royal Carribean International: “Radiance of the Seas“
