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Page 1: PRECISE LOAD SHARING MODULE - Ambac …...principal load, a single generator. Load Sharing The load sharing unit is an electronic equivalent of the watt-meter (see Figure 3). The inputs

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EngineGoverning Systems

Page 1

ENGINEGOVERNING SYSTEMS

IN E R N A TIO N A L

LS 671A SECTION EG 70-10

PRECISE LOAD SHARINGMODULE

LS 671ASection EG 70-10

PRECISE LOAD SHARINGMODULE

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EngineGoverning Systems

Page 2: PRECISE LOAD SHARING MODULE - Ambac …...principal load, a single generator. Load Sharing The load sharing unit is an electronic equivalent of the watt-meter (see Figure 3). The inputs

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EngineGoverning Systems

Page 1

ENGINEGOVERNING SYSTEMS

ir-_ T E R N A T I O N A L

"" LS 671A SECTION EG 70-10

INTRODUCTIONThe LS 671A Precise Load Sharing Module is an accessory outputs, a multiple arrangement of generator sets can bedevice used in conjunction with the AMBAC International connected in parallel to share load equally. The moduleEngine Governing system. It measures the true power can also be used to control the power output of one oroutput of an AC generator and converts this output to a more generator sets delivering power to an infinite bus.proportional DC voltage. By proper connections of the

SPECIFICATIONSLS 671A PRECISE LOAD SHARING MODULE PERFORMANCE CHARACTERISTICS

--Load Sharing .................................................... Adjustable to within +2% between sets--Performance ........................................... Isochronous or droop paralleling and power control

POWER INPUT--AC Signal ........................................... 208 or 416 volt (nominal) line-to-line, 5 amp., CTS,

with minimum 12.5 VA rating (internal 0.5 ohmburden resistors).

--Supply ......................................... 10 VDC from terminal K of "C" series speed control unit--Line-to-Line Voltage ..................................... HZ LOW RANGE ItIGIt RANGE

Min Max Min Max

_'_ *50 70 104 140 208*60 85 130 170 260

50 140 208 280 41760 170 260 340 500

400 170 260 340 500

*Low range input voltages can be accepted as long as CTsecondary current is limited to 3 amps at maximum ratedload. If higher voltages must be used, external PT's can beadded. The transformer burden capability is insignificant.

ENVIRONMENTAL--Temperature Range ................................................. -550 to + 85°C (-650 to + 185°F)--Relative Humidity ....................................................................... up to 100%--Case .............................................................. Fungus proof and corrosion resistant

PHYSICAL--Dimensions ............................................................................ See Figure 1--Weight ............................................................................ 1.5 kgs (3.3 lbs)--Mounting ........................................................ Any position (See Installation Page 6)

RELIABILITY--Tested ...................................................................................... 100%--Vibration ................................... All printed circuit boards are conformally coated on both sides.

Printed=nLJSA Page 1 IssuedAu_4usl!989

INTRODUCTION

SPECIFICATIONS

The LS 671A Precise Load Sharing Module is an accessry device used in conjunction with the AMBAC International Engine Governing system. It measures the true power output of an AC generator and converts this output to proportional DC voltage. By proper connec-

tions of the outputs, a multiple arrangement of generator sets can be connected in parallel to share load equally. The module can also be used to control the power output of one or more generator sets deivering power to an infinite bus.

LS 671A PRECISE LOAD SHARING MODULE PERFORMANCE CHARACTERISTICS -Load Sharing………………..……………………………………………………Adjustable to within ± 2% between sets -Performance………………………………………………………..Isochronous or droop paralleling and power control

POWER INPUT -AC Signal………………………………………..........................…208 or 416 volt (nominal) line-to-line, 5 amp., CTS, with minimum 12.5 VA rating (internal 0.5 ohm burden resistors). -Supply…………………………………….……………………10 VDC from terminal K of “C” series speed control unit - Line-to-Line Voltage…………………………………………..

ENVIRONMENTAL -Temperature Range……………………………………………………………….………-55º to + 85ºC (-65º to + 185ºF) -Relative Humidity…………………………………………………………………………………………………up to 100% -Case………………………………………………………………...................……Fungus proof and corrosion resistant

PHYSICAL -Dimensions………………………………………………………………………………………………………See Figure 1 -Case……………………….............................................…………………………………………………15. kgs (3.3 lbs)

RELIABILITY -Tested………………………………………………………………………………………………………………….…100% -Vibration………………………………..………………All printed circuit boards are conformally coated on both sides.

Page 1

HZ

*50*605060400

LOW RANGE HIGH RANGEMin7085140170170

Min140170280340340

Max104130208260260

Max208260417500500

Low range input voltages can be accepted as long as CT secondary current is limited to 3 amps at maximum rated load. If higher voltages must be used, external PT’s can be added. The transformer burden capability is insignificant

*

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EngineGoverning Systems

Page 3: PRECISE LOAD SHARING MODULE - Ambac …...principal load, a single generator. Load Sharing The load sharing unit is an electronic equivalent of the watt-meter (see Figure 3). The inputs

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EngineGoverning Systems

ELECTRIC GOVERNOR

CT1

CT2

CT3

LOAD SHARINGSENSITIVITY

DROOPLOAD ANTIC

ADJUSTADJUST

PARALLELCABLEJUMP FOR

DROOP TOGOVERNOR

DESCRIPTION

Figure 1. LS 671A precise load sharing module dimensions

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

A single engine generator set operating on an isolated load may run well isochronously. Thus, under all load conditions, the steady state frequency of the generator is the same. The only deviations from this stead state frequency are caused momentarily by sudden load changes or transients. However if two engine generator sets are used to supply power in parallel to a single load, the two generators are forced to run at exactly the same speed and in phase with each other. When two genera-tors are connected in parallel and supplying a common load, any tendency of one unit to get out of phase with the other is resisted by the magnetic forces (synchroniz-ing torques) within the generators as if they were connected with a chain drive.

If each of the two engines in parallel was controlled by an isochronous governor each would try to force its speed to be the same as its reference. Although two isochronous governors could be set to nearly the same frequency, it is not possible for their references to be exactly the same. Under those circumstances the two engines must run at some average speed. The firse engine whose governor references is at a slightly higher frequency will try to increase its power generation. On the other hand, the second engine with its governor set slighly below the average speed, will keep decreasing throttle in order to slow down. The net results is that in a short time, the first engine will be taking all the load it can and the second engine will be dropping off as much as it can until its generator begins acting as a motor which will drie the second engine.

R H K

TEST POINTS185mm7.2812

13mm0.5”

10mm0.375”

52mm2.0625”

141mm5.5625”

152mm6”

8mm0.3125” TYP.207mm

8.1562”7mm

0.2656” DIA. -4 HOLES

416

208

1 2 3 + -

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EngineGoverning Systems

Page 4: PRECISE LOAD SHARING MODULE - Ambac …...principal load, a single generator. Load Sharing The load sharing unit is an electronic equivalent of the watt-meter (see Figure 3). The inputs

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EngineGoverning Systems

To force the engines to carry equal loads, true power measuring devices, called Precise Load Sharing Mod-ules(LS 671A or LS 672A), are used (see Figure 2).

This modules takes the voltage and current of each of the three phases of the generator and develops a DC voltage proportional to true power. The oltages of the several sets are averaged and the voltage difference between the average power and the actual power of each set is sent to the reference point of each speed control unit. Thus, if a given engine generator set tends to generate at a power level different from its porportion-ate share, a correction voltage is sent to its governor reference to correct its power. Since there is as much positive as negative correction, the overall system remains isochronous. This system is very accurate and is independent of actuator and throttle characteristics. However it can be applied only where each set as its principal load, a single generator.

Load SharingThe load sharing unit is an electronic equivalent of the watt-meter (see Figure 3). The inputs to the load sharing units are line to line voltage, line currents and battery supply. Nominal voltages of 208 or 416 volts (measured from line to line) can be used. Lower voltages can be accepted by adjusting the CT ratios (See specifications on page 1). If higher voltages must be used, external PT’s will be required. Battery supply is for operation of the realy circuits.

Line current inputs are usually from existing CT’s which may be part of the ammeter circuits. Accurate instrument CT’s with secondary ratings of 5 amps and a minimum volt-amp ratings of 12.5 VA should be used. Due to wire resistance in the CT lines to the load sharing unit, the volt-amp rating of the CT must be increasted according-ly. Output of the load sharing unit is a DC voltage proportional to real load. This voltage can be measured at terminals 14 and 15 (15 negative) or test points shown in Figure 1 and ranges from 0 to about 8 volts depending on engine load and CT ratios.

Maxmimum voltage measurement will be obtained when the sensitivity control is full CW. All the load sharing units are connected in parallel via the parallel cable (terminals 14 and 15). If any voltage difference between paralleled units exists, a small DC current will flow in the parallel cable. This current will cause the respective speed control units references to be set to a slightly difference speed, some raised, some lowered. Since the increases in reference speeds are balanced by the decreases, the system speed remains un-changed. Only the load will change in the direction to reduce the paralleling cable current to a minimum. The sensitivity control can be used to match the generator power output of each unit to others.

CURRENTSENSING

TRANSFORMER

MAINGENERATOR

CURRENTSENSING

TRANSFORMERMAIN

GENERATORPRIMEMOVER

THROTTLEFLYWHEELGEAR

ACTUATOR

MAGNETICSPEEDSENSOR

30CURRENTSENSING

30VOLTAGE

SENSING

SPEEDCONTROL

UNIT

LOADSHARINGCONTROL

(TRUE POWERMEASUREMENT)

SPEEDCONTROL

UNIT

PRIMEMOVER

ACTUATOR

MAGNETICSPEEDSENSOR

30CURRENTSENSING

30VOLTAGE

SENSING

FLYWHEELGEAR

PARALLEL CABLE

THROTTLE

CIRCUITBREAKER

CIRCUITBREAKER

LOAD

LOADSHARINGCONTROL

(TRUE POWERMEASUREMENT)

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EngineGoverning Systems

Page 5: PRECISE LOAD SHARING MODULE - Ambac …...principal load, a single generator. Load Sharing The load sharing unit is an electronic equivalent of the watt-meter (see Figure 3). The inputs

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EngineGoverning Systems

Figure 3. Power measuring circuitLoad AnticipationA load anticipation signal is included in the module to minimize speed transients. An internal control is provid-ed to adjust the sensitivity of the load anticipation signal. CW rotation of the adjustment increases sensitivity.

DroopWhen paralleling with an infinite bus droop is often used. An internal control is provided for droop adjustment and is located under the dot plug on the cover.

POWER CONTROL - SINGLE GENERATORControl of the power output from a generator that is operated in parallel with an infinite bus can be accom-plished by using the load sharing unit to provide power control to the speed control unit. An engine generator system which will operate under isochronus speed control in standby operation and under load control when in parallel with a main bus automatically is shown in Figure 4. Many variations of the power control circuit can be constructed, but the principle is usually the same. The load sharing is connected to the generator as shown in Figure 4. The generator is synchronized and connected in parallel to the main with no load on the generator. As soon as the auxiliary contacts are closed, the load sharing unit’s output voltage is zero (units sensing no load). The speed control units speed setting will automatically be set higher than the synchronous speed. The ending load will quickly rise along with the voltage output of the parallel cables. When the parallel cable voltage has reached the power control bias voltage the speed control unit will be reset back to

synchronous speed, the limiting the load. The engine load can be adjusted using the power bias control to any level from zero to full load.

POWER & LOAD TRANSFER CONTROL FOR SEVERAL GENERATORS

A singly power and load transfer control for several generators paralleled to the utility main can be added by following the connections and circuits shown in Figure 5. The circuit depicts load shawing connections for two generators but additional generators may be added with more respectove conntections of 30k resistor to terminal “R” of the speed control units and terminals 14 and 15 of all LS 671A load sharing moduls connected in parallel. Terminal 16 of the additional LS 671A load sharing modules should be connected to terminal “R” of their corresponding speed control untis. The load transfer control including the 100K droop resistor remains unchanged as additional units are added. The power level accepted by all generators can be set by closing the load transfer switch and manually adjusting the load trasfer control. The power transferred from the utility mains will be shared by the generators to the proportion previously set for each LS 671A load sharing module. Refer to “Adjustments, Load Sharing.” Full load from the utility main can be transferred by moving the adjustment of the load transfer control toward the maximum position until the utility main is carrying no load. The utility main can be disconnected from the generators once full load is transferred with minimum electrical disturbance. Once separated the unloading switch

30 VOLTAGE

30 CURRENT

WATTMETER

SENSITIVITYADJUST

5K

10K

CW

DROOPADJ

+

-

JUMPERFOR

DROOP

+

-

PARALLELCABLE

FROM(TERMINAL “K”)

OUTPUT (TERMINAL “R”)

GROUND (TERMINAL “H”)DIFFERENTIAL

AMPLIFIER

OF “C” SERIESSPEED CONTROLUNIT

13

14

15

18

16

17

10VREF

+

TERMINALS

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EngineGoverning Systems

Page 6: PRECISE LOAD SHARING MODULE - Ambac …...principal load, a single generator. Load Sharing The load sharing unit is an electronic equivalent of the watt-meter (see Figure 3). The inputs

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EngineGoverning Systems

Page 5

CURRENTTRANSFORMERS

3 PHASEGENERATOR

A

B C

MAINBUS

MAIN CIRCUITBREAKER

CLOSES WITHMAIN BREAKER

LS 671A

208 VOLTSLINE TO LINEUSE 2, 4 & 6

416 VOLTSLINE TO LINEUSE 1, 3 &5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 C SERIES CONTROLUNIT TERMINAL

5K

25K

5K

POWERCONTROLBIAS

KR (J ON-230

10.2 VDCREF IN

+

H - (GROUND)

should be turned off to eliminate any droop. The separa-tion of the utility main from the generators allows the load transfer control to be used as a frequency control for all the engine/generator sets. Speed changes can be made simultaneously without affecting load sharing adjustment. Load can be transferred manually to the utility main from the generators by closing the unloading switch. The

engine/generator sets are synchronized to the utility mains by using the load transfer control to match the generator frequency by changing engine speed. The main breakers can now be closed and the load transfer control moved toward the minimum position until the generators are carrying no load. When the engine/gener-ator sets are delivering no power, the can be removed from service.

Figure 4. Wiring for generator power control bias adjustment circuit

Figure 5. Load transfer schematic

LS 671A LS 671A

SpeedControl Unit

MIN5K

MAX

UNLOADINGSWITCH

SpeedControl Unit

PARALLEL

ISOLATED

CW

620Ω

LOADTRANSFERCONTROL

30K30KK H

R

100K

R

161415

1614

15

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EngineGoverning Systems

Page 7: PRECISE LOAD SHARING MODULE - Ambac …...principal load, a single generator. Load Sharing The load sharing unit is an electronic equivalent of the watt-meter (see Figure 3). The inputs

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EngineGoverning Systems

ENGINEGOVERNING SYSTEMS

ENTE RNATIONAL

LS 671A SECTION EG 70-10

INSTALLATIONt

The LS 671A Precise Load Sharing Module is wired to the ing have 0.1 ohms resistance, this will raise the demand ongenerator and to the speed control unit as per wiring the CT's by 20%, based on 0.5 ohm burden resistors. Thusdiagram (see Figure 6). The module is typically found in the it is recommended that the resistance of each wire be heldcontrol cabinet with the instrumentation and controls. The below 0.1 ohm. The parallel cable operates with low voltagepower resistors will dissipate up to 40 watts, so the natural and low current so almost any cable typically used onflow of cooling air must not be obstructed, engines will suffice. It is recommended that some care be

taken not to allow leakage currents between the parallelThe wiring to the generator must be of appropriate size to cables or from the parallel cables to ground or other cir-carry the voltage and current to the load sharing units. The cuits. Such leakage can cause unwanted droop.voltage sensing connections 1 thru 6 require low currents

The output (terminal 16) which connects to the speed con-(less than 200 mA), so wire size and quality consistent trol unit terminal "R", may require a shielded cable if this iswith good mechanical installation is recommended. not a direct connection of short length. The speed control

Terminals 7 thru 12 are part of the CT circuits and require unit connection (terminal "R") is quite sensitive, so carecurrents up to 5 amps to operate the load sharing. If the must be taken on leads attached to terminal "R" that strayresistance of the cables connecting the CT's to the load shar- fields of leakage to other terminals are not present.

_'_TO "R" (TO "J" ON-23) _)OF "C" SERIES

FOR -__FROM "K" (+10V REF) UNIT

DROOP lLS 671A \ + -

II1=13141'.].,, • l_J 1. lj" ,,II,I-HI _ _ : PARALLEL CABLE2(_8VOLTS .=

LINE TO LINE I ]_,_ " - _ _ COMMON TO ALL

[ " I "- "- LOAD SHARING ASSYSUSE 2.4 & 6 I OPEN FOR SINGLE _ AUXILIARY

UNIT OPERATION CONTACTSI CLOSES WITHI

, , __USE 1, 3 & 5 [ II II •

I [ MAIN CIRCUIT ]II j I

MAIN

,-- I 3 PHASE

CURRENT/_ - I GENERATORTRANSFORMERS

Figure 6. Wiring to LS 671A precise load sharing module

Printed _n U S A Page 6 issued August, 1989

INSTALLATION

Page 6

The LS 671A Precise Load Sharing Module is wired to the generator and to the speed control unit as per wiring diagram (see Figure 6). The module is typically found in the control cabinet with the instrumentation and controls. The power resistors will dissipate up to 40 watts, so the natural flow of cooling air must not be observed.

The wiring to the generator must be of appropriate size to carry the voltage and current to the load sharing units. The voltage sensing connections 1 thru 6 require low currents (less than 200 mA), so wire size and quality consistent with good mechanical installation is recon-mended.

Terminals 7 thru 12 are part of the CT cicuits and require currents up to 5 amps to operate the load sharing. If the resistance of the cabls connecting the Ct’s to the load sharing have 0.1 ohms resistance, this will raise the

demand on the CT’s by 20%, based on 0.5 ohm burden resistors. Thus it is reconmended that the resistance of each wire be held below 0.1 ohm. The parallel cable operates with low voltage and low current so almost any cable typically used on engines will suffice. It is recon-mended that some care be taken not to allow leakage currents between the parallel cables or from the parallel cables to ground o other circuits. Such leakage can cause unwanted droop.

The output (terminal 16) which connects to the speed control unit terminal “R”, may require shielded cable if this is not a direct connection of short length. The speed control unit connection (terminal “R”) is quite sensitive, so care must be taken on leads attached to terminal “R” that stray fields of leakage to other terminals are not present.

Figure 6. Wiring to 671A precise load sharing module

CURRENTTRANSFORMERS

3 PHASEGENERATOR

A

B C

MAINBUS

MAIN CIRCUITBREAKER

PARALLEL CABLECOMMON TO ALL

LOAD SHARING ASSYSAUXILIARYCONTACTS

CLOSES WITHMAIN BREAKER

OPEN FOR SINGLEUNIT OPERATION

JUMPERFOR

DROOP

TO “R” (TO “J” ON-23)FROM “H” (GROUND)FROM “K” (+ 10V REF)

OF “C” SERIESSPEED CONTROLUNIT

LS 671A

208 VOLTSLINE TO LINEUSE 2, 4 & 6

416 VOLTSLINE TO LINEUSE 1, 3 &5

+ -

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

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EngineGoverning Systems

Page 8: PRECISE LOAD SHARING MODULE - Ambac …...principal load, a single generator. Load Sharing The load sharing unit is an electronic equivalent of the watt-meter (see Figure 3). The inputs

®

EngineGoverning Systems

ENGINEGOVERNING SYSTEMS

_ATIONAL

LS 671A SECTION EG 70-10

ADJUSTMENTS

CAUTION: With the system at no load, adjust each generator set forzero real power output reading on the generator set watt-THE ENGINE SHOULD BE EQUIPPED WITH ANmeter using the speed trim adjustment. Then adjust theINDEPENDENT OVERSPEED SHUTDOWN

MECHANISM TO PREVENT RUNAWAY WHICH voltage regulators to trim the reactive current on theCAN CAUSE EQUIPMENT DAMAGE OR generator set ammeter to zero. Load can now be applied to

the system. If instability occurs, see "Troubleshooting".PERSONNEL INJURY.

Load Sharing

CAUTION: Once the system has load applied, it is important that eachHIGH VOLTAGE PRESENT ON TERMINALS 1-6. engine share the system load proportionally. Check the

DO NOT power output of each generator set that is reflected by eachOPEN CIRCUIT CT's AS HIGH VOLTAGE generator set wattmeter. Turn the Load Sharing Sensitivity

WILL BE PRESENT. Adjustment CCW. The generator set carrying least load canbe adjusted by turning the engine's Load Sharing SensitivityAdjustment CCW until its share of the load has been picked

Preset the sensitivity control on each load sharing unit to the up.full CW position. Set the load anticipation adjustment full Changing the speed trim adjustment of any individual unitCW. All the engine-generator set speed control units should will have the effect of adding or subtracting power frombe adjusted to the desired speed before load sharing is that particular unit and raising or lowering the systemattempted. Use the speed trim to accomplish this. With a DC frequency slightly.voltmeter, measure the voltages across terminals 14 (+) and

_'/ 15 (-) with a load applied to the generator. A voltage of Load Anticipationabout + 8 volts will represent full load with 5 amps CT The load sharing units have a load anticipation circuit toinput. Instrument polarity must be observed. Momentarily, improve transient response. The load anticipation adjustmentshort the individual CT's (7 to 8, 9 to 10, 11 to 12) one at a is factory set at zero sensitivity (full CW). The load anticipa-time with an insulated lead. The voltage read on the tion should be adjusted while the engines are in parallel.voltmeter will fall by about 1/3for each individual shorting Carefully advance the control CCW while occasionally pok-of a CT. If these voltage drops do not occur, it indicates ing the throttle or changing load. Instability or overshootimproper phasing of the CT's and/or voltage connections may result if the control is advanced too far.which must be corrected. Make sure power is off beforemaking corrections. During CT phasing, voltage Droopmeasurements, while individual CT's are being shorted, can After disconnecting the parallel cable, 5 % adjustable droopbe conveniently made at test points shown in Figure 1 with with load is obtainable by adding a jumper from terminalright hand test point being (+) positive. 13 to 14. The jumper applies a direct short circuit to

the parallel cable connection. Adjust the droop control toOnce the proper CT phasing has been verified, the generator the desired droop level. It is linear and may be set at anysets may then by synchronized manually with the speed trim load.control or with the AMBAC automatic phasing synchronizer.Once synchronized, the generator sets can be paralleled.

TROUBLESHOOTINGInstability, when the units are paralleled, may occasinally If instability is still present, the gain adjustment on the speedresult. The instability can be caused by the sensitivity of the control unit may be reduced slightly or it is possible that theload sharing being too high. Turn all the sensitivity controls voltage regulator is marginally stable and adjustment of theCCW proportionately until stability is restored. The system voltage regulator is required. Refer to the voltage regulator

d should stabilize with the controls no more than 75% CCW. manufacturer's instructions for adjusting the regulator forparallel operation.

Pnnled tn U S A Page 7 Issued Augusl 1989

Page 7

ADJUSTMENTS

TROUBLESHOOTING

Preset the sensitivity control on each load sharing unit to the full CW position. Set the load anticipation adjustment full CW. All the engine-generator set speed control units should be adjuste to the desired speed before load sharing is attemtped. Use the speed trim to accomplish this. With a DC voltmeter, measure the voltages across terminals 14 (+) and 15 (-) with a load applied to the generator. A voltage of about +8 voltes will be represent full load with 5 amps CT input. Instrument polatirty mus be observed. Momentarily, short the infividual CT’s (7 to 8, 9 to 10, 11 to 12) one at a time with an insulated lead. The volatage rad on the voltmeter will fall be about a 1/3 for each individual shorting of a CT. If these voltage drops do not occur, it indiacts impoper phasing of the CT’s and/or voltage connections which must be corrected. Make sure power is off before making corrections. During CT phasing, voltage mea-surements, while individual CT’s are being shorted, can be conveniently made at test points shown in Figure 1 with right hand test point being (+) positive.

Once the proper CT phasing has been verified, the generator set may then by synchronized manuall with the speed trim control or with the AMBAC automatic phasing synchronizer. Once Synchronized, the genera-tor sets can be paralleled

With the system at no load, adjust catch generator set for zero real power output reading on the generator set wattmeter using the speed trim adjustment. The adjust the voltage regulators to trim the reactive current on the generator set ammeter to zero. Load can no be applied to the system. If instability occurs, see “Troubleshoot-ing”.

Load SharingOnce the system has load applied, it is important that each engine share the system load proportionally. Check the power output of each generator set that is reflected by each generator set wattmeter. Turn the Load Sharing Sensitivity Adjustment CCW. The genera-tor set the carrying least load can be adjusted by turning the engine’s Load Sharing Sensitivity Adjustment CCW until its share of the load has been piced up.

Changing the speed trim adjustment of any individual unti will have the effect of adding or subtracting power from that particular unit and raising or lowering system frequency slightly.

Load AnticipationThe load sharing units have a load anticipation circuit to improve transient response. The load anticipation adjustment is factory set at zero sensitivity (full CW). The load anticipation should be adjusted while the engines are in parallel. Carefully advance the control CCW while occasionally poking the throttle or changing load. Instability or overshoort may result if the control is advanced too far

DroopAfter disconnecting the parallel cable, 5% adjustable droop with load is obtainable by adding a jumper from terminal 13 to 14. The jumper applies a direct short circuit to the parallel cable connection. Adjust the droop control the desired droop level. It is linear and may be set at any load.

Instability, when the units are paraleled, may occasional-ly result. The instability can be caused by the sensitivity of the load sharing being too high. Turn the sensitivity controls CCW proportionately until the stability is restored. The system should be stabilized with the controls no more than 75% CCW. If instability is still

present, the gain adjustment on the speed control unit may be reduced slightly or it is possible that the voltage regulator is margainally stable and adjustment of the voltage regulator is required. Refer to the voltage regulator manufacturer’s instructions for adjusting the regulato for parallel operation

CAUTION:THE ENGING SHOULD BE EQUIPPED WITH AN

INDEPENDENT OVERSPEED SHUTDOWNMECHANISM TO PREVENT RUNAWAY WHICH

CAN CAUSE EQUIPMENT DAMAGE ORPERSONAL INJURY.

CAUTION:HIGH VOLTAGE PRESENT ON TERMINALS 1-6

DO NOTOPEN CIRCUIT CT’S AS HIGH VOLTAGE

WILL BE PRESENT.

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EngineGoverning Systems

Page 9: PRECISE LOAD SHARING MODULE - Ambac …...principal load, a single generator. Load Sharing The load sharing unit is an electronic equivalent of the watt-meter (see Figure 3). The inputs

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EngineGoverning Systems

TROUBLESHOOTING

If the load sharing function does not operate properly, the fault may be found by preforming the following tests.

PROBABLE TROUBLE1. Improper relative phasing at A.C. inputs2. Wiring to current transformers reversed.

1. Improper adjustment of Load Sharing Sensitivity Control.2. Excessive (>0.1 ohm) or unequal resistance in connections to current transformers.3. Excessive noice on A.C. line.4. Adjusment required at generator set’s voltage regulator.

STEP TERMINALS NORMAL VALUE PROBABLE CAUSE OF ABNORMAL READING

10.2 ± 0.5 VDC(reference input)(6.2 VDC with ECQ seriesspeed control.)

1. Speed Control Unit not turned on.2. Error in wiring to speed contorl unit.3. Defective speed control unit.

1 18, 17

14, 152 8 VDC at full load withthe sensitivity control CW.(Parallel Cable)

1. Improper relative phasing at A.C. inputs2. Used the high voltage range inputs (terminals 1, 3, 5) instead of low range (terminals 2, 4, 6).3. Excessive resistance (>0.1 ohm) in wiring to current transformers (C.T.).4. Improper C.T. ratios.

Page 8

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EngineGoverning Systems


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