Self-regulatingbrushlesssynchronous alternatorsseries DSG

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Contents:

Application

Ratings

Definition of the alternator3.1 Basic technical data3.2 Enclosure3.3 Type of cooling3.4 DesignMechanical design4.1 Design4.2 Housing and stator4.3 Rotor4.4 End shields4.5 Bearings4.6 Terminal boxPower reducing influences5.1 Standard conditions5.2 Relation between power and coolant

temperature5.3 Relation between power and installation

altitude5.4 Relation between power and power factor

cos phi5.5 Marine classification5.6 Higher types of enclosure

5.6.1 Enclosure IP 435.6.2 Enclosure IPR 44 or IPR 545.6.3 Enclosure IP 44 or IP 54

Electrical performance6.1 Operating principle

6.1.1 Alternator6.1.2 Voltage regulator

6.2 Self-excitation, de-excitation6.2.1 Self-excitation6.2.2 De-excitation

6.3 Voltage and frequency6.3.1 Voltage setting range6.3.2 Static voltage response6.3.3 Transient voltage response6.3.4 Voltage waveform

6.4 Currents6.4.1 Unbalanced loads6.4.2 Overload6.4.3 Short-circuit behaviour

6.5 Non-linear load6.6 Emergency operation

6.6.1 Emergency manual control6.6.2 Stand-by regulator

Parallel operation7.1 General7.2 Parallel switching conditions7.3 Start-up synchronisation at isolated

parallel operation7.4 Steady-state operation/load distribution

7.4.1 Voltage droop7.4.2 Power factor regulation

7.5 Mains parallel operation7.6 Oscillations7.7 Neutral currentPlanning guidelines8.1 Nominal capacity8.2 Dynamic voltage variation8.3 Non-linear load

Factory testing9.1 Standard tests9.2 Special tests

9.

AvK SEG competencein electricity generationand protective relaying

When it comes to electricitygeneration and protectiverelaying, AvK|SEG is your com-petent and reliable partner. Weoffer the quality and flexibilityof a medium-sized, indepen-dent group of companies witha good mixture of experienceand innovation. Operatingglobally, we are able to offeryou custom-built engineeringsolutions as well as an exten-sive range of products.Our product range extends

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from individual protectiondevices to complete electricalfit-outs for power plants. AvKGermany, with its factory inIngolstadt and the site inDreieich near Frankfurt, sup-plies synchronous machinesand converters, while SEGKempen specialises in plantengineering and devices forprotection and other functions.Together we set standardsand so influence electricitygeneration technology on aninternational scale. We offerevery performance level, re-gardless whether you requirean individual device, analternator or a turnkey system.Our efficient customer serviceand advice centres through-out the world work energetically

to meet your needs, as werely not only on continuityand quality in our technologysolutions, but we also con-sider your satisfaction asequally important.The certification to DIN ENISO 9001 that AvK and SEGfactories have underpins ourhigh quality aspirations.

The AvK alternators of seriestype DSG are the result of an advanced developmentprocess in which efficientmanufacturing methods aswell as many years experiencein the applications of suchsynchronous alternators wereutilised.

This applies to the mechanicaldesign, electrical characteris-tics and control engineeringproperties.

The DSG series was devel-oped with particular regardto optimal operating efficiency,and to very favourable dy-namic response in the eventof load surges. Furthermore,for the magnetic circuitdesign, damper cage layoutand winding design, specialemphasis was laid on minimalreaction as a result of currentharmonics on the voltagewaveform.

The following lists justsome of the areaswhere AvK synchronousalternators from theDSG series 29-144 areused in the energysector:

��permanent power supply of stationary and maritime systems

��peak load operation inparallel with the mains

��emergency power sup-ply for critical users, e.g. in power plants,industrial plants, hospitals,high-rise buildings

��on-board power supplyfor ships

��ship shaft generators,reversing machines

��diesel-electric drive forships

��special power suppliesfor users who place highdemands on supply-linequality

��frequency conversion,e.g. 50:60 Hz or60:50 Hz

Suitable for use in all kinds of drives: diesel engines, gas engines, gas, water andsteam turbines as well as shipshaft generators.

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Application

1.

Self-regulating brushlesssynchronous alternators of the series type DSG

Application examples

Deutscher

Akkreditierungs

Rat

TGA-ZQ-004/92-00

C E R T I F I CAT E

DET NORSKE VERITAS ZERTIFIZIERUNG UND UMWELTGUTACHTER GMBH

certifies that the company

AvK Deutschland GmbH & Co. KG

in

D – 85051 Ingolstadt

has established a

quality system

in conformity with

DIN EN ISO 9001, 8.94

This Certificate is valid for:

Design, manufacturing and commissioning of

synchronous generators up to 30MVA,

asynchron motors and frequency converters

This Certificate is valid until:

2001-01-31

Certificate-Registration-No.:

ESN06940AQ98

Essen, 1998-01-09

Essen, 1998-01-09

M. Fröhlich

K. Nordhause

Manager

Lead-Auditor

This Certificate is only valid in connection with the original Certificate ESN06940AQ98.

Stand 01/98 D / &74924

Emergency power supply

On-board supply

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Ratings

2.

Offshore equipment

Standard use ranges as perVDE 0530, degree of pro-tection IP 23, rated criteriaaccording to Section 3.1

� 30 – 4,000 kVA,400/231 V, 50 Hz,1,500 rpm

or

� 33 – 4,500 kVA,450/260 V, 60 Hz,1,800 rpm

Furthermore, DSG alternatorsare available for all standardvoltages to VDE 0530 in the performance range givenand also as special versionsfor specific voltages. In addi-tion, the following rotationalspeeds are available, de-pending on power and size:

� at 50 Hz – 1,000, 750,600 and 500 rpm

� at 60 Hz – 1,200, 900,720 and 600 rpm

Higher ratings up to approx. 6.5 MVA with660 V or 690 V are possibleon request.

Combined heat and power station

Designed in accordancewith DIN-EN 60034, VDE 0530, IEC 34

3.2

EnclosureIEC 34-5 DIN VDE 0530-5

IP 23 provided as standard.Depending on size, highertypes of enclosure e.g.IP 43, IPR 44, IPR 54,IP 44 and IP54 can beprovided as required, seeSection 5.6.

3.3

Type of coolingIEC 34-6, DIN VDE 0530-6

Provided as standard:IC01/IC0A1.In the event of special pro-tection requirements, the type of cooling will beadapted accordingly.

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Definition of the alternator

3.

3.1

Basic technical data

Rated power: According to rated output values

Rated power factor: cos phi = 0.8

Rated voltage: 230…1000 V

Rated frequency: 50 Hz or 60 Hz, Special frequencies on request

Coolant temperature: ≤ 40°C (VDE)

Installation altitude: ≤ 1,000 m above sea level (VDE)

Degree of protection: see 3.2

Type of cooling: see 3.3

Design: see 3.4

To ensure the alternatorsmeet the desired requirements,conditions and specifications,deviations from this data andVDE 0530 are possible onrequest. The alternators canbe produced to all interna-tional standards such as BS4999, CIE 2/3, NEN3173, NEMA, etc., seeSection 5.5.

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B 3IMB 3IM 1001

B 3/B 5IMB 35IM 2001

B 20IMB 20IM 1101

B 14/B 20IMB 24IM 2101

B 5/B 20IMB 25IM 2001/IM 1101

B 16IMB 16IM 1305

B 2IMB 2IM 1205

V 1IMV 1IM 3011

3.4

DesignIEC 34-7 DIN VDE 0530-7

Sizes DSG 29 to DSG 74are produced as standardin the designs IMB 34,IMB 24 and B2/B5 orB5/B16.Sizes DSG 86 to DSG 144are available as standard in designs IMB 3, IMB 20and IMB 16.Other designs are possible.On request, we will performspecial feet dimensions in order to meet the require-ments of the gen-set baseframe.

Design B3 B3/B14 B3/B5 B20 B14/B20 B5/B20 B2 B16 B2/B5 B5/B16 V1 Special design

Code I IMB IMB IMB IMB IMB IMB IMB IMB _ _ IMV1DIN IEC 34 – 7 3 34 35 20 24 25 2 16

Code II IM IM IM IM IM IM IM IM _ _ IMDIN IEC 34 – 7 1001 2101 2001 1101 2101 2001/1101 1205 1305 3011

DSG29 – 52

� � � � � �

DSG62 – 74

� � � � � � � � � � � �

DSG86 – 114

� � � � � � � � � � � �

DSG125 – 144

� � � � � � � � � �

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Mechanical design

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Shaft

Antifriction bearing, drive end

Inner bearing cap

End shield, drive end

Fan

Stator housing

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Cover

Rectifier support

Terminal box

Terminal studs

Shaft

Outer bearing cap

Grease regulation disc

Antifriction bearing, drive end

Inner bearing cap

End shield, drive end

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Fan

Stator housing

Main alternator stator

Main alternator rotor

Exciter stator

Exciter rotor

End shield, non-drive end

Antifriction bearing, non-drive end

Cover

Rectifier support

Terminal box

Low voltage terminals

Main alternator stator

Main alternator rotor

Exciter stator

Exciter rotor

End shield, non-drive end

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DSG 29 – 43

DSG 52 – 99

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Antifriction bearing, non-drive end

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Shaft

Labyrinth seal

Sleeve bearing, drive end

Sleeve bearing shell

Oil ring

Machine sealing

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End shield, drive end

Fan

Stator housing

Main alternator stator

Main alternator rotor

Exciter stator

Exciter rotor

End shield, non-drive end

Sleeve bearing, non-drive end

Rectifier cover

Rectifier support

Terminal box

Low voltage terminals

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DSG 114 – 144 with sleeve bearings

Shaft

Outer bearing cap

Grease regulation disc

Antifriction bearing, drive end

Inner bearing cap

End shield, drive end

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End shield, non-drive end

Antifriction bearing, non-drive end

Rectifier cover

Rectifier support

Terminal box

Low voltage terminals

Fan

Stator housing

Main alternator stator

Main alternator rotor

Exciter stator

Exciter rotor

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DSG 114 – 144 with antifriction bearings

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4.1

Design

The alternators consist of themain alternator as revolving-field machine, the excitermachine as revolving ar-mature machine, and theelectronic voltage regulator.The components are con-structed as a compact unit.The voltage regulator isprovided built-in as standardin the main terminal box(DSG 29 – 52), in the non-drive end shield (DSG 62 –99) or in a separate terminalbox (DSG 114 – 144), ormay be provided separatelyupon request for enclosedmounting into a switch-board.

Cooling:At all machines, the coolingair is drawn in on the non-drive end, and blown out onthe drive end by means of the shaft-mounted fan.

Overspeed:In accordance with VDE0530, the alternators aredesigned to withstand aoverspeed of 1.2 times therated speed for 2 minutes.For higher runaway speeds,e.g. in the case of waterturbines (1.8 x nN [ratedspeed]), the required designmodifications will be made.Circuit engineering pre-cautions for protection of thesystem have to be arrangedwhere required.

4.2

Housing and stator

The stator laminated coreconsists of layers of low lossdynamo sheet metal, held byclamping rings or clampingplates. The stator as a wholeforms a compact, stable unitconsisting of stator laminatedcore and housing cover. Thehousing is constructed as an octagonal steel structurefor the smaller units DSG 29– 52, and in the case of thebigger machines, as a roundwelded construction. The feetof the DSG 29 – 99 modelsare welded to the housing,while in the case of the largermachines in the DSG 114 –144 series, they are integratedinto the end shields.

The stator winding correspondsto temperature classification“H” as per DIN EN 60034-1or VDE 0530-1.

Fastening components andmechanically stable con-nections secure winding

overhangs and connectorsagainst the dynamic stressgenerated by electrodynamicforce.

4.3

Rotor

The main rotor designed assalient pole execution con-sists of hydraulically com-pacted sheet metal or steelplates. The standard built-indamper cage is connectedelectrically in the pole shoesand between the poles. Thewinding of the main rotor ismade of flat copper and isamply protected by suitablysized components againstdeformation caused bycentrifugal force. The uni-directional fan is located atthe drive end of the rotor.

The exciter rotor consists ofdynamo sheet metal, withthe three-phase windinginserted into its slots. Therotating diodes in 6 pulsebridge connection areconnected on the input sideto the 3-phase winding ofthe exciter and on the out-put side to the field windingof the main machine. Theyare amply dimensioned interms of voltage and currentloads and also providedwith a suppressor circuit.

The rotor windings complywith temperature class “H”of DIN EN 60034-1 VDE0530-1. The shaft ends arecylindrical in types IMB 3 or IMB 20, with slot and keyas per DIN 6885 Sheet 1.The rotor is balanced withhalf key in accordance withVDE 0530/IEC 34-14 asstandard.

At alternators with shaft flange,e.g. design IM 1205 (B2)or IM 1305 (B16) or atmachines with flexible steeldiscs, flanged shafts or steeldiscs will be adapted to therespective drive motor. Othershaft designs or a secondshaft end can be manufacturedon request.

4.4

End shields

Sizes DSG 29 to DSG 144are equipped with weldedor cast-iron end shields.

DSG 29 – 99:Alternator feet attached inclose proximity to the bearingsand designed accordingly,guarantee an especiallysolid base. The drive endshield is produced from greycast iron up to and includingsize DSG 62, and fromDSG 74 is of a weldedconstruction (standard intype B14). Flange bells withmotor fixing dimensions to SAE standards can beattached to it.

DSG 114 – 144:The alternators are fixed tothe baseframe or foundationat the end shields, thealternator feet are integratedinto the end shields. Bothend shields are screwed to the stator housing andtogether form the completealternator housing.The generally large intakeareas cause a slight pressureloss and therefore a lowcooling air flow velocity. Interms of filter use, this resultsin long maintenance intervals.

4.5

Bearings

Up to and including size 43,pre-lubricated antifrictionbearings with at least25,000 hours operating lifeare built in. As an option,bearings allowing re-lubrication are available.From size DSG 52 up, re-lubrication antifrictionbearings with a calculatedlife span for steady-statebasic operation of at least40,000 hours (up to sizeDSG 62) or 30,000 hours(from size DSG 74) are in-stalled as standard. Up tosize DSG 74, the antifrictionbearings are generallyprestressed, while the largerseries machines contain pre-stressed bearings dependingon the application and require-ments.DSG alternators of twin-bearing design are equippedwith a fixed bearing and afloating bearing. The positionof the fixed bearings andfloating bearings dependson the size and the designfactors.DSG alternators of single-bearing design have afloating bearing on the non-drive end.Sizes DSG 74 to DSG 144can be equipped uponrequest and at additionalcost with sleeve bearingsflanged to the end shields.Depending on the operatingconditions, forced oil lubri-cation or water-cooling canbe required here.

Appropriate precautionsprotect all bearings duringtransport. In addition, forsafety reasons, we providesleeve bearing alternatorswithout oil filling for transport.

4.6

Terminal box

The main terminal box isperformed according toenclosure IP 54. Dependingon size, it may be on top(size DSG 29 to DSG 74),on the side if the customerprefers, on the top of thegenerator housing (DSG 86to DSG 99), or on the sideor above at the non-driveend shield with the desiredcable outlet.For the series DSG 29 toDSG 36 all 6 winding endsare led to separate terminals,while for the larger productseries, the neutral point isconnected as standard tothe winding overhang andis led to a common neutralterminal or neutral busbar.From size DSG 62, anopen neutral point can beincorporated if required,together with an enlargedterminal box, for examplefor mounting of current trans-

formers for differential pro-tection and measurements.In the case of built-in currenttransformers from AvK/KWK,a copper busbar constitutesthe fourth terminal (N).The auxiliary and low voltageterminals are either onseparate terminal strips in the main terminal box, in theend shield at the non-driveend, or in a separate terminalbox on the stator housing,depending on alternatorsize. Voltage regulators,

temperature sensors,secondary outputs of currenttransformers, measuringlines for the exciter current,heating and suchlike can beconnected here. The heating terminals whichcarry current when the unit is at rest are insulated forthe protection of operatingpersonnel.

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Main terminal box DSG 114

Auxiliary terminal box DSG 114

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5.3

Relation betweenpower andinstallation altitude:Characteristic curve 5.3

As both air density andtherefore heat absorptivitydecrease at higher altitudes,either the performance mustbe decreased or a largergenerator must be chosen.

5.1

Standard conditions

The unit ratings given arevalid under VDE conditions,that is:Coolant temperature≤ 40°C,Installation altitudeH ≤ 1000 m above sealevel, alternators of standardenclosure IP 23 and coolingtype IC01.

5.2

Relation betweenpower and coolanttemperature:Characteristic curve 5.2

The temperature limit of thewinding is critical. A de-crease in the coolant tempera-ture (coolant temperature < 40°C) leads to an increasein performance, while atemperature increase (coolanttemperature > 40°C) leadsto a decrease in performance.The characteristic values of the particular alternatorselected, for example re-actances, are generally validfor the given rated power (SN).

Power reducing influences

5.

∂ [°C]

Relation between power and coolant temperature Characteristic curve 5.2 Relation between power and installation altitude Characteristic curve 5.3

5.5

Marine classifications

As the coolant temperatures(CT) are higher and the permis-sible rises in temperature arelower than the specificationsfor land-based applications,the performance rating shouldbe lowered, or a larger gen-erator type chosen.

The table opposite shows per-missible rises in temperature;design and use according totemperature class “H” or “F”.For higher types of enclosurethan IP 23 and other require-ments, please send us a de-tailed inquiry.

Temperature class Cooling air Temperature DeratingClassification temperature rise factor SN/STYP

CT δϑ for series DSG°C K 29…74 86…99 114…144

“H“ VDE 40 125 1 1 1GL 45 120 0.96 0.96 0.96

RINA 50 115 0.93 0.93 0.93LR 45 110 0.90 0.90 0.90

NKK 45 110 0.90 0.90 0.90DNV 45 115 0.93 0.93 0.93BV 50 110 0.90 0.90 0.90

ABS 50 115 0.93 0.93 0.93MRS 45 1201) 0.96 0.96 0.96

“F“ VDE 40 105 0.86 0.91 0.93GL 45 100 0.83 0.87 0.89

RINA 50 90 0.75 0.84 0.86LR 45 90 0.75 0.84 0.86

NKK 45 90 0.75 0.84 0.86DNV 45 90 0.75 0.84 0.86BV 50 90 0.75 0.84 0.86

ABS 50 95 0.78 0.84 0.89MRS 45 1001) 0.83 0.87 0.89

5.4

Relation betweenpower and powerfactor cos phi:Characteristic curve 5.4

The underexcited range ofcos phi = 0 –1 is limitedduring:

� single operation bymaintaining the ratedvoltage using the voltageregulator

� operation in parallel withthe mains by stabilityagainst loss of synchronism

The overexcited range islimited by:

� cos phi = 1 –0.8by the performance of the drive motor

� cos phi = 0.8 –0by the permissible rotortemperature rise.

Limitation by alternator

Limitation by prime mover

underexcited overexcited

Relation between power and power factor cos phi Characteristic curve 5.4

1) temperature rise reduced in order not to exceed VDE

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5.6

Higher types ofenclosure

The design and electricalparameters are determinedduring the project stage. Thedegree of enclosure and the rated power are indicatedon the rating plate.

5.6.1

Enclosure IP 43

Enclosure type IP 43 is poss-ible for all sizes and requiresthe addition of air inlet filters,whose higher air resistancereduces the performance byabout 5% – 10% (dependingon the size, rotational speedand air velocity). Temperaturesensors in the generatorwhich are to be connectedto a control unit in thecontrol panel warn againstan unacceptable temperaturerise in the winding whencleaning of the air filters isrequired.

5.6.2

Enclosure IPR 44 orIPR 54

From size DSG 62, air intakeand outlet ducts may beprovided. As an extra ad-vantage, in addition to thehigher degree of enclosure,the necessary ventilationdissipates the heat throughducts from the installationarea and also reduces thenoise level.The position of the intakeand outlet openings in thegenerator allows for theconnection of supply andoutlet air channels. Themagnitude of the permissiblepressure drops in the pipingis to be agreed with themanufacturer.

5.6.3

Enclosure IP 44 orIP 54

These types of enclosure arealso possible for size DSG62 and above and requirethe use of heat exchangers.For the alternator, the coo-ling air temperature emergingfrom the cooler and into thealternator is the decidingfactor.

� Water-cooled heatexchangers:In general the heatexchangers are usuallydesigned so that thetemperature of the coo-ling air entering thealternator is 15 K abovethe water intake tempe-rature. The change inperformance is given incharacteristic curve 5.2.There is no additionalpower reduction causedby increased air resistancein the cooling circuit.

� Air-cooled heat ex-changers:In this case, the coolingair temperature emergingfrom the cooler andentering the alternator ishigher than the outsidetemperature by the tem-perature gradient in theheat exchanger. It isusually designed so thatthe cooling air goinginto the alternator isaround 15 K higherthan the air entering the cooler. The powerreduction is given incharacteristic curve 5.2.If the customer requiresa more space-savingcooling system design,a reduction in per-formance may benecessary because ofthe resulting increase inair resistance. Carefulevaluation and appro-priate case by case typedetermination is recom-mended.

6.1.1

Alternator

In the smaller models, the G1stator windings are madefrom round wire, while thoseof the larger models aremade from flat wire as pre-formed windings. The G3winding is also located in the main stator. From sizeDSG 52 up, the well-propor-tioned terminal box allows forthe addition of supplementarycontrollers or modules. The G1 rotor winding, madeof section wire, is laid directlyonto the insulated rotor lami-nated core. This gives anoptimal copper filling factorand good mechanicalstrength. The strength of theimpregnated coils is furtherincreased by mechanicalpacking.The three-phase rotor windingof the G2 stationary-fieldmachine, and its field wind-ing, are insulated like the wind-ings of the main machine.High-quality multi-layer surfaceinsulation materials are usedto insulate the windings. Thisheat-resistant insulating systemis suitable for the mechanical,electrical and climatic re-quirements of land and shipuse. The G3 auxiliary fieldwinding supplies the fieldwinding of the G2 brushlessthree-phase a.c. exciter with

6.1

Operating principle

Electrical performance

6.

Main alternator

Exciter machine

Auxiliary winding

Voltage droop transformer

Voltage adjuster

G1

G2

G3

T6

R1

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power via the actuator of the voltage regulator.The power generated in the3-phase winding of the ex-citer rotor is rectified in athree-phase bridge connectionconsisting of silicon diodesand supplied to the rotor ofthe G1 alternator. For varyingload, the voltage of the mainalternator is regulated byaltering the excitation currentin the G2 winding using thetransistor actuator of the voltageregulator.

6.1.2

Voltage regulator

An electronic voltage regu-lator is used for high voltageaccuracy and excellentdynamic response. An aux-iliary winding in the mainstator supplies the regulatorwith power.

In order to sense unequalphase voltages with unbal-anced loads, the alternatorvoltage is measured at 3 phases for all regulatormodels. The voltage regulatorkeeps the terminal voltageat the main machineconstant via the excitationcurrent IK1 in the winding of the G2 exciter.

The following regulators areused as standard:

� for sizesDSG 29 to 43, the“COSIMAT LC1” regulator

� for sizesDSG 52 to 62, the“COSIMAT LC2” regulator

� from sizeDSG 74 on, the“COSIMAT N+” regulator.

If required, the “COSIMATN+” regulator can also beused for sizes DSG 29 to62. When installing the“COSIMAT N+” into machinesof sizes DSG 29 to 43, theregulators and componentsare generally built in to theswitchgear, while the terminalboxes of sizes DSG 52 to62 offer sufficient space fora “COSIMAT N+” and amaximum of 2 supplementarymodules. Even for externalassembly, the voltage regu-lators are always to be con-figured so that their powercircuits have cooling airflowing freely through them.The low-pass filter requiredwith harmonics load may be incorporated into theterminal box for all productsin the range.

6.1.2.1

“COSIMAT LC1”

The “COSIMAT LC1” is acompact voltage regulatorfor the regulation of three-phase synchronous alternatorsin single operation.Essential features of the“COSIMAT LC1” regulatorare:

� three-phase voltagemeasurement

� internal and externalalternator voltage setpoint adjustment

� PID gain control amplifierwith freely adjustable Pand I parameters

� underspeed protection(overproportional voltagedrop at underfrequency)with LED display

� resistance against environ-mental effects due toencapsulated electronics

� long operating life due tohigh quality components

� compact design

6.1.2.2

“COSIMAT LC2”

The “COSIMAT LC2” is acompact voltage regulatorfor the regulation of three-phase synchronous alter-nators in stand-alone andparallel operation. Essentialfeatures of the “COSIMATLC2” regulator are:

� three-phase voltagemeasurement

� internal and externalalternator voltage setpoint adjustment

� PID gain control amplifierwith freely adjustableP and I control parameters

� parallel operation byreactive current-dependentvoltage droop

� adjustable underspeedprotection with LED dis-play

� resistance against environ-mental effects due to en-capsulated electronics

� long operating life due tohigh quality components

� compact design

6.1.2.3

“COSIMAT N+”

The “COSIMAT N+” voltageregulator, used from sizeDSG 74 up, is a standardisedcomponent, subjected to en-durance testing for electricalfunctioning and temperature-rise behaviour by the manu-facturer before installation inthe alternators.The capacity of the regulatoris geared to the requirementsof bigger machines. Apartfrom having those propertiesalready described for the“COSIMAT LC2” regulator,it is also possible to addsupplementary regulatorsand modules to the “COSIMAT N+” regulator.

The control signals for thefollowing functions aresupplied via terminals onthe “COSIMAT N+”:

� power factor regulation/balancing

� reactive power regulation/balancing

� regulation to a mainsinterface point

� operating range extension

� automatic or manualstand-by changeover

� volts-per-Hertz regulation

can be ignored for normaldistances between assemblyand control panel.The set point potentiometeris connected to the regulatorterminals s/t. The connectionlines of the set point po-tentiometer must be laid outseparately as double-coreshielded wires. For correctequipotential bonding, theshield must be connected to earth at either end ormore often. The minimumwire size must be 0.75 mm2.The optical shield coveringmust reach at least 80…85%.For the operating rangebetween no-load and fullload, as per VDE 0530 andIEC 34, the voltage range(0.95…1.05) x UN applies,with the given constraints.

6.3.2

Static voltage response

The voltage tolerance for allDSG alternators is ±0.5% to ±1% under the followingconditions/disturbances:

� no-load operation to ratedload cos phi 0.11)… 1

� cold and warm machines

� speed drop ofapproximately 3%.

1) This concerns the regulationproperties. The thermal rating forcontinuous operation is at cos phi = 0.8. The usual operationalrange is cos phi = 0.8…1.

6.3

Voltage and frequency

AvK alternators are built for 50 or 60 Hz operationat the voltages given in VDE 0530 and specificationsfrom other countries. However, other voltages orfrequencies are availableon request.

6.3.1

Voltage setting range

The voltage adjustment pro-vided as standard for alter-nators of sizes DSG 29 toDSG 43 is achieved by a rheostat located on theregulator.Alternators of size DSG 52and up are provided asstandard with a 500 Ω set-point adjuster. This is built in to the terminal box inunits up to size 74, and islocated in the control panelin the case of bigger units(also an option for sizesDSG 29 to DSG 74) forexpediency reasons. Thevoltage is continuously adjust-able within the range ±10%of rated voltage. As perVDE 0530, the control rangeis ±5% of the rated voltagein no-load operation; it canbe extended to ±10% foroperational testing of controlpanel components and forsynchronisation. The resistanceof the potentiometer cables

6.2.2

De-excitation

For de-excitation, the currentin the G2 exciter windingmust be brought to 0. Thiscan be done by disconnect-ing the connections UH1 andWH1 at the “COSIMAT LC2”,or by opening the bridgeUH1-UH1´ and WH1-WH1´on the “COSIMAT N+” voltageregulator. In this way, thesupply to the regulator is inter-rupted and the current in theexciter field falls to zero. Forsizes 74 – 144, the de-ex-citation switch should beconnected to the designatedterminals (see wiring diagramlegend), and not to the“COSIMAT N+”, by use of ade-excitation relay.Encapsulated switches are to be used. The minimum loadof the contacts must be > 5 VDC/0.1A. The required ratedload is 220 V AC/10 A.Please note carefully the in-structions in the appropriatewiring diagram.

Caution:The excitation field electriccircuit of G2 must not beinterrupted! After the de-excitation, the alternatorproduces a further residualvoltage of approx. 15% ofUN. This value, particularlyfor voltages of over 400 V,can be above the permit-ted touch voltage!

� stator current limiting

� excitation current limiting

� cable compensation

More detailed descriptionsof these devices are givenseparately.

6.2

Self-excitation,de-excitation

6.2.1

Self-excitation

Self-excitation without theuse of external auxiliarymeans is achieved throughpermanent magnets in theframe of the exciter.In addition, excitation canbe provided by an externalvoltage of approx. 10 V DC(positive pole on the I ter-minal). This voltage isapplied to the terminals I1 – K1 of the exciter duringthe run-up to rated speed.

The external excitationmust not be switched onwhen the machine is atrest.

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6.3.3

Transient voltageresponse

see Oscillogram 1 Application see Oscillogram 2 Shedding

The voltage change forsudden load variationsdepends on the leakageresistance voltage drop ofalternator G1.The magnetic circuit and the winding are optimallydesigned for slight transientvoltage changes.

External disturbances fortransient voltage changeare the relative current surgeas well as the power factor.For example, during fullload application with cosphi 0.8, the transient voltagedrop is approximately18…25%. The lower valueapplies to machines at1500 rpm, the higher valueto low-speed machines of 500 rpm. With existingbase load, the transientvoltage change is slightlylower than that for a alternatoroperating at no load.

The time constants of thealternator G1, the exciterG2, and the control systemused as well as the dynamicspeed decrease as an ex-ternal influence determinethe temporal path of thevoltage. The amply dimen-sioned excitation systemachieves short recovery timesbecause the excess excitation

from the power supplyequipment works up until therated voltage is achieved.

The recovery time is0.5…0.8 seconds, depend-ing on alternator size.

6.3.4

Voltage waveform

A sinusoidal voltage wave-form is produced by thegeometry of the magneticcircuit and the choice of thewinding factor of the statorwinding.

The usual definitions are:

� Telephone Harmonic Factor “THF”

The requirements of VDE0530 are easily achieved.

� total harmonic distortion

The harmonic content betweenPh-Ph is ≤ 3% during no-loadoperation up to ratedpower and power factorcos phi = 0.1…1 atsymmetric and linear loads.

If required, a special wind-ing arrangement reducesthe total harmonic distortionto less than 3% and thesingle harmonics part to lessthan 2% even for the voltagewaveform between line andneutral. However, this resultsin a slight reduction in perfor-mance.

Oscillogram 1 / load application

Oscillogram 2 / load shedding

Alternator DSG 99 L1-6, 3220 kVA, 450 V, 60 Hz, 1200 rpmRemoval of 2600 kVA, cosϕ = 0.8

Alternator DSG 86 L1-4, 2840 kVA, 400 V, 50 Hz, 1500 rpmApplication of 1500 kVA cosϕ = 0.1

current is a factor of 1.37higher, and for a phase-to-earth fault a factor of1.85 higher. In this way,protective devices can beco-ordinated to isolate the faulted system safelyand selectively.

� The range IK ≥ 3 x IN isrequired for example ingeneral by various clas-sification societies. Theassociated exciter ratingleads to a short-term voltagerise almost to ceiling voltagewhen the short-circuit iscleared. This (high) voltagerise may also occur duringcertain disturbances in thevoltage control system.

� Necessary measures for the protection ofconsumers are providedfor in the control panel.

6.4

Currents

6.4.1

Unbalanced loads

The electrical layout of thealternator also permits anunbalanced load.

The following unbalancedloads, with no loading onthe other phases, are allowed:

mately 10 seconds with-out the rated voltagedropping to an unaccept-able level. This short-termoverload capacity isavailable for starting currentsof induction motors, forexample.

6.4.3

Short-circuit behaviour

� The corresponding machineparameters determine themagnitude of the asymmet-ric short-circuit current.Depending on machinesize, it decreases within0.3…0.6 seconds to the sustained short-circuitcurrent.

� The standard componentsare dimensioned so thatthe alternator can supply2.5 to 4 times the ratedcurrent as sustained shortcircuit current for 3 secondsat a 3 phase terminalshort circuit. When a 2phase short circuit occurs,the sustained short-circuit

Consequently, the ratio ofthe negative sequence sys-tem I2 to the rated current IN is clearly above the VDErequirements.Unbalanced loads causevoltage unbalance andadditional losses that areparticularly noticeable whenthere are temperature risesin the damper cage. There-fore, the load should bedistributed on the system-sideas symmetrically as possible

between the 3 phases. Thevoltage asymmetry will beabout ±1% per each 10%unbalanced load. If the otherphases were also loadedwith different currents, themagnitudes of the positivephase sequence system,negative sequence system,and zero phase sequencesystem must be analyticallyor graphically calculated,so that the actual alternatorload may be determined.For the alternator, the currentin any phase winding maynot exceed the rated currentand the ratio of the negativesequence system I2 to therated current IN must remainless than 20%.

AvK recommends limitingI2/IN to ≤ 0.08 in line withthe relevant specifications for the protection of the entiresystem.

6.4.2

Overload

� In accordance with VDE0530, the generators aredimensioned for 1.5 timesthe rated current for aduration of 30 seconds.

� To adapt to the requirementsof internal combustionengines, an overload of1.1 times the rated currentcan be maintained for 1hwithin 6h.

� The amply dimensionedexcitation equipment permitsa short-term overload ofup to about 1.8 times therated current for approxi-

thisSize corresponds to

I/IN I2/IN

29 1.0 0.33

36 1.0 0.33

43 0.9 0.3

52 0.75 0.325

62 0.6 0.2

74 0.6 0.2

86 0.6 0.2

99 0.6 0.2

114 0.6 0.2

125 0.6 0.2

144 0.6 0.2

I2 = inverse current

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Path of the short circuit current for 3 phase short circuit of an alternatorDSG 125 K1-12, 2740 kVA, 400 V, nominal current Inominal = 3,955 Awith connected voltage regulator

Oscillogram/asymmetric short-circuit current

20

6.5

Non linear load

Converters as consumerswith non-linear currents causeharmonics in the voltagewaveform. In order to keepthe losses occurring in thealternator and the system lowand to guarantee the correctfunctioning of the connectedelectrical devices, the har-monic oscillation content ofthe voltage waveform shouldbe as small as possible, seealso Section 6.3.4.That presupposes a smallsub-transient reactance xd”.One of the ways this canbe achieved is by design-ing the damper cage in aparticular way.

With very high load partdue to inverters, over-dimensioning of the alternatormay be necessary. This alsorequires a specific magneticcircuit design. This inevitablyleads to an increase of the asymmetric short-circuitcurrent.The measures to be con-sidered for the alternatordepend on the relative nonlinear load, the current har-monics brought about bythe user, and the permissibleharmonic voltage distortion.

It is advisable to consult themanufacturer in order tooptimise the entire system.

6.6

Emergency operation

Where stricter safety require-ments exist, it is possible, inthe event of failure of the elec-tronic voltage regulator, to con-tinue to operate the alternatorusing an emergency manualcontrol or to change over to a stand-by regulator eithermanually or automatically.

6.6.1

Emergency manualcontrol

The electrical power fromthe supply equipment is fedto the exciter winding I1 – K1of the exciter G2 via anadjustable transformer withseries-connected rectifier. Manual control of the correctexciter rating proves extremelydifficult, especially in thecase of inrush currents. There-fore, emergency manualcontrol is only possible wherethere is almost constant loadof a separate network or inthe case of operation inparallel with the mains. Toavoid consequential damagecaused by operator error andbecause of the difficulty ofmanual operation, the alter-nator must be changed backto automatic voltage regu-lation as soon as possible.

6.6.2

Stand-by regulator

The disadvantages ofemergency manual controldo not apply when a stand-by regulator is installed,because the alternator canoperate as before afterswitchover to this regulator.The entire regulator unit –main regulator, stand-by regu-lator, manual or automaticchangeover unit – must bebuilt in to the switchgear.

7.1

General

Alternators from size DSG52 and up are equipped as standard for paralleloperation.The smaller sizes DSG 29to DSG 43 can be upgradedaccordingly.The parallel operation of the required number of unitsenables an optimal capacityutilisation and favourableoperating efficiency.In addition, the operationalreliability of the system in-creases since the other unitscan take over in the case offailure of one of the units aftercorresponding pre-setting.

7.2

Parallel switchingconditions

Alternators to be connectedin parallel to each other orto the mains must fulfil thesynchronisation conditions,i.e. be identical with regardto the following criteria:

� voltage� frequency� phase sequence� phase position

Permissible tolerancesbefore connection are:

� voltage difference:5% of UN

� frequency difference:2% of fN

Parallel operation

7.

The frequency toleranceapplies to normal dieselgenerator sets. Foroperating mode with ad-ditional flywheel, a lowervalue is permissible.

To avoid incorrect synchron-isation (e.g. by unqualifiedoperational personnel), asynchronisation control deviceshould be fitted which shallonly release the circuit breakerin the control panel if thesynchronisation conditionsdescribed are met.

Automatic synchronisation is generally recommendedto avoid causing possibledamage.

After parallel connection,the active power load andreactive load distributionmust be balanced.

7.3

Start-up synchron-isation at isolatedparallel operation

This function can only beused with similar types ofmachines, and requiressimultaneous start-up of thediesel generator sets. Thealternators are connectedelectrically to each otherwhile at rest. As rotationalspeed increases, the alter-nators are excited andattempt to pull themselvesinto synchronisation. Theexcitation current duringinput of the initial excitation(12VDC) has to be limitedso that the circulating currents

flowing in the UVW mainlines until synchronisationoccurs do not exceed therated current.The exciter boosting currentis usually drawn from aseries resistance and isolatingdiodes of a battery and fedto the exciter field connectionsI1/K1, in parallel with theregulator connections. The resistance and the ratedpower of the series resistancedepend on the battery voltagelevel and the no-load ex-citation of the alternator. Inaccordance with Section6.2 “De-excitation”, regu-lator supply is interruptedduring acceleration andreleased again when therated speed is reached. The voltage produced bythe regulator at terminalsI1– K1 then exceeds thebattery voltage. A blockingdiode in the battery feedline prevents backflow intothe battery, which can thenbe disconnected. Throughthe firing speed recognition,an inactive alternator maybe disconnected.A supplementary currentlimiting regulator SR can be used for automatic limit-ing of the stator current.

7.4

Steady-state operation/load distribution

� For active power loaddistribution, the rotationalspeed behaviour of the driving machine isresponsible.

� For reactive load distribu-tion, the voltage response ofthe alternators is responsible.

The following methods ofreactive load distribution canbe used:

7.4.1

Voltage droop

After a synchronous alternatoris connected in parallel, it isno longer possible to carry outvoltage regulation becauseof the fixed mains voltage.Minor variations in the mainsvoltage would result in con-siderable alternator reactivecurrents. Therefore, forparallel operation, a drooptransformer must be insertedin phase “V” of the alternator.With this current signal, areactive-current dependentset point control is achievedin the voltage regulator.Mains voltage fluctuations ofup to ±2% can be equalised.

Alternators from size DSG52 up are fitted as standardwith a current transformer forvoltage droop. Smallermachines can be upgradedaccordingly. Through the useof the droop, the terminalvoltage is lowered dependingon the reactive current. Thepower proportional reactive

load distribution requires thesame droop.

The power factor dependenceof the droop ensures that for parallel operation withthe mains and duringchanges in the mains voltage,the apparent power changesin permissible limits.

At the rated current, thedroop is:

0.0% for cos phi = 11.3% for cos phi = 0.91.8% for cos phi = 0.83.0% for cos phi = 0

Experience shows that stableparallel operation can beachieved when the droop inthe plant is adjusted to 3%for nominal current and cosphi 0.1. For adaptation with othermanufacturer’s products, thedroop can be steplessadjusted between 0%…6%of the nominal voltage.

7.4.2

Power factorregulation

This process basically requiresthe use of the “COSIMATN+” base regulator (asstandard from size DSG 74up, as a retro-fit for smallergenerators) and is usedduring operation in parallel

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22

with the mains where thesupply voltage fluctuatesgreatly. An additional regu-lator for cos phi regulationin the alternator or in theswitchgear directly besidethe base regulator controlsthe “Cosimat N+” voltageregulator of the alternator forthe purpose of maintainingthe set power factor, i.e. the alternator voltage willfollow the system voltageautomatically.

7.5

Mains paralleloperation

As in most cases the mainshas a much higher short-circuit power than the alter-nators, the number of unitsrunning in parallel is irrelevant,i.e. there is no noticeableeffect.Voltage fluctuation is thusnearly always determinedby the grid.

For a variation in mainsvoltage ΔU ≤ ±2%, thedroop in accordance withSection 7.4.1 applies.

For a variation in mainsvoltage ΔU ≥ ±2%, a cosphi regulator in accordancewith Section 7.4.2 is used,so that through the influenceof the exciter, the alternatorvoltage automatically follows

the mains voltage and holds the set power factorconstant during voltagefluctuations as well as duringdifferent alternator loads. Ifa specific power factor isrequired at the mains inter-face point, the cos phi regu-lator effective transformer mustbe configured at this point.However, it is also possibleto use a specific mainscoupling regulator QPF-NK.So as not to overload theexciter circuit, an excitationcurrent limiter is advisable. It limits the excitation currentto the set value for the ratedpower for cos phi = 0.8.There is a further possibilityof influencing the reactivepower supply specifically bya reactive power regulator.With regard to permissiblelonger voltage and frequencyvariations, the specificationsin VDE 0530-1, Section12.3, Figures 10 and 11apply. If the voltage and frequencydeviate from the rated values,there will always be highertemperatures at constantrated power and thereforereduced durability of thewinding and thus of thewhole machine. Voltagerises cause higher irontemperatures in the mainmachine, which transfers tothe winding. Voltage dropsmean increased current andtherefore increased heatingof the windings. Sinceexceeding the temperature

permissible for the respectiveheat class always reduces thewinding durability, prolongedoperation on the limits ofrange A in DIN VDE 0530-1should be avoided. This canbe assured if the machine isdimensioned and operated in accordance with theoperating data specified atthe project stage.

7.6

Oscillations

These periodic active andreactive power fluctuationsare caused by irregulartorque characteristics in the reciprocating internalcombustion engines. To dampen these variationsduring parallel operation, a damper cage is built into all the DSG alternators asstandard.

7.7

Neutral current

For different voltage wave-forms of the alternatorsrunning in parallel as wellas the voltage waveforms of the grid, there are mainly 3rd order currentssuperimposed on the funda-mental wave in all 3 wind-ing phases. These flow backthrough the neutral. Themagnitude of these currentsdepends on the potentialdifference of the ripplevoltage and the reactanceof the alternator.

Since the winding and theneutral conductor are loadedthermally in this manner, thiscurrent must be reduced bya neutral choke.

Alternatively, by using 2/3chorded double-layer wind-ings (standard with some 4pole DSG models) a transientcurrent can largely beavoided. If identical gen-erators run in parallel in iso-lated operation, no neutralchoke is generally necessarysince the voltage waveformsare identical between Ph-Mp.

8.1

Nominal capacity

The nominal capacity resultsfrom the sum of all users con-sidering the service factor.The necessary unit rating isdetermined after considerationof the power-reducing in-fluences in accordance withSection 5.

8.2

Dynamic voltagevariation

A standard value used is ΔU ≤ 20%. In this way,sufficient clearance is avail-able for retaining voltage of normal contactors.Deviations from this value inthe various specifications or as a result of further re-quirements must be consideredon a case by case basis.For the determination of thedynamic voltage dip, theinrush current with powerfactor must be known. Inrushcurrents worthy of furtherinvestigation mainly occurwhile connecting inductionmotors.

Suggested typical values are:

Squirrel-cage motors: Direct on-line starting

ΔS=(5 – 6) x SN at

cos phi 0.2 – 0.4Star delta connectionΔS=(1.7 – 2.0) x SN at

cos phi 0.2 – 0.4Depending on the loadtorque during acceleration,

bigger power stepscan occur during the starto delta switchover.

Slip ring motors:Start-up with armature resis-tance

ΔS=(1.3 – 1.6) x SN at

cos phi 0.2 – 0.4 The inrush currents aresmall and mostly non-critical for dynamic voltagechanges.

Transformer connection:For transformer unit ratingbigger than alternator unitrating, consultation with thefactory is required. The highstart-up rush of the trans-formers causes a load similarto a short-circuit. Depending on requirements, the inrushcurrent should be attenuatedby resistors or the transformershould be magnetised withrising generator excitation.This is generally advised inthe case of unit-connectedtransformers.

8.3

Non-linear load

Caused by harmonics, in-creased losses occur in thealternator and the connectedusers. For clarification, themagnitude of the harmonicsload, the current harmonicdistortion as well as thepermissible voltage harmonicdistortion are to be con-firmed to the manufacturer.

All DSG alternators are sub-jected to a full test runaccording to VDE guidelines.The tests are logged and thetest reports made availableto the customer.

9.1

Standard tests

1. Measuring the coldresistances

2. Measuring the residualvoltage

3. Voltage symmetry

4. Phase sequence test

5. Load characteristic with cos phi = 0.1

6. Range of the setpointadjuster/voltageadjustment range

7. Voltage regulator

7.1 Adjustment of thevoltage regulator

7.2 Underspeed protectionadjustment

7.3 Parallel operationadjustment

8. Transient overload with cos phi = 0.1 orat short circuit

9. Winding test

10. Overspeed test at120% nominal speed

11. High voltage test

12. Measurement ofinsulation resistances

13. Adjustment of additionalvoltage regulatormodules

Final inspection:

General design, testing ofthe components, wiring in-spection, rating plate, circuitdiagrams, identifications,anti-condensation heating,temperature sensors, etc.

9.2

Special tests(at extra charge)

Further tests can beperformed on request.Please ask if required.

1. No-load characteristic

2. Short circuit characteristic

3. Determination ofefficiency (summation of losses)

4. Temperature-rise test

5. Noise measurement

6. Load connection andload disconnection

7. Harmonics contentanalysis

8. Peak short-circuit test

9. Sustained short-circuitcurrent measurement

10. Vibration measurement(cardan-driven or atmotor operation)

11. Rotor leakage test withrotor removed (inductor)

Planning guidelines

8.

Factory testing

9.

23

Subject to technicalmodifications.

PB D

SG 5

0600

E

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