Features

Quality System Certification

� Compatible with AMBAC,GAC, Cummins EFC andBarber Colman speedcontrollers

� Isochronous load sharing ofparalleled generators

� Forward and reverse powermonitors and relay contacts

� Load anticipation� Power measurement with

internal and externaldisplays

� Power factor/phasingindicator

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The LS7010 Load Share Unit is a multifunction load sharing and powercontrol module intended to be used in generator set applications requiringisochronous paralleling and/or mains power control. Isochronous loadsharing is it�s primary purpose.

The LS7010 uses a new electronic method of 3-phase power measurementwith higher accuracy and increased reliability. Opto-isolation of the highvoltage inputs is provided for safety and it can work with smaller, lower costcurrent transformers (down to 1.25VA) than previous designs It utilizesthe industry common parallel cable output method to balance the absorbedloads.

A unique feature of the LS7010 is that it is provided with two outputs toconnect to speed controllers. One of these outputs interfaces with AMBACand other manufacturer�s similar controllers. The second output has theopposite phase and can connect directly with Cummins EFC and BarberColman controllers.

Provisions for power monitors and relays are provided which can be set totrip for various conditions such as at preset forward and reverse powerlevels. A built-in LED bar graph indicates the genset power level and canbe combined with an external meter to obtain a more exact value. OtherLED indicators clearly show the status of inputs, outputs and internalsignals to allow easy setup and troubleshooting.

Conforms to EC Directive on

Electromagnetic Compatibility

AMBAC International, 103 Myron Street, West Springfield, MA 01089 (USA) - North America Tel: (800) 683-7991 Fax: (800) 683-7992International Tel: (413) 781-2204 Fax: (413) 739-0935 For Technical Assistance: (413) 785-6804

Figure 1. Outline Dimensions

Model LS7010Load Share Unit

Fwd, Rev Power Monitors

Caution Note:C o n n e c t i o n sillustrated aresuggested only. Allcomponents andwiring must beselected andinstalled inconformance withlocal regulations.

Figure 3. F

unctional Block D

iagram

Performance Specifications

EG-LS7010 5/99Printed in U.S.A.

Consult Factory for Other Options

Ordering Information

LS7010

Standard UnitModel Number

Notes1 All output specifications

are based on 5 amps fromthe current transformer (CT)secondaries at full load

2 All printed circuit boardsare fully conformallycoated

DescriptionThe LS7010 reads the voltage and current of each of the three phases of the generator and develops a

DC voltage proportional to the real power component of the line currents. By connecting similar DC voltagesfrom all gensets on the power bus, via the �parallel cable�, the LS7010 measures the difference between theaverage power of all the gensets and the actual power of its genset. The LS7010 sends an output signal,based on this difference, to the speed controller which forces the genset to match the average power,thereby sharing load equally among the gensets. This system is very accurate and is independent ofactuator and throttle characteristics.

The inputs to the LS7010 are line voltage, line currents and battery supply. AC line voltage between 100volts and 500 volts can be used in two ranges: 100-240 VAC and 240-500VAC. The proper voltage range iseasily selected using a dip switch. Line current inputs are usually from existing current transformers ( CT�s)which may be part of the ammeter circuits. DC battery supply voltage range is 12 - 31VDC.

Included are both Reverse and Forward Power monitor circuits which sense when generator power isnegative or positive respectively and activate relay contacts. Both monitors have adjustable trip points andtime delays built in. The power levels at which the Forward Power monitor trips ON and OFF are separatelyadjustable such that the relay contacts may be used to automatically determine when to add or removegensets from the power bus.

A DC voltage signal proportional to generator real power is indicated on the power display bar graph andis available for connection to an external meter. A group of six LED indicators (two for each phase) areprovided on the left side of the case to indicate the power factor and phasing of the line inputs.

A reversed output mode is available to be used when the LS7010 is monitoring the mains in peak shavingapplications. If the monitored power supplied by the mains tends to be too high, the speed controller(s) issignaled to increase generated power. An adjustable load anticipation signal is also included in the LS7010to minimize speed transients.

Figure 2. Typical Connections

Outputs

Load Sharing typ Adjustable to within ±2% between sets1

Operating modesIsochronous and droop paralleling and powercontrol

Reverse Power MonitorAdjustable from 2 to 20% with a time delayadjustable from .5 to 15 sec.1

Forward Power Monitor"ON" trip point adjustable from 20 to 100%"OFF" trip point adjustable from 0 to 80%Delay adjustable from .4 to 30 sec.1

Power Output Signal(can be calibrated with internal pot)

0 to -2 volts DC representing reverse power0 to 5.5 volts max DC representing forward power

Forward and Reverse Power relaycontact ratings

max Form C, 10A 290 VA

Inputs

AC SignalTwo selectable ranges accomodate 100 to 500Vrms line to line

Supply Voltage 12 to 30 Vdc

Polarity Negative ground, case isolated

Power Consumption max 200 mA

Environmental

Operating Temperature range -40°C<T<+80°C (-40°F<T<+176°F)

Humidity Up to 95%2

Vibration 5g @ 20 to 100 Hz

Enclosure Fungus proof and corrosion resistant

Physical

Dimensions See Figure 1

Weight 2.4 lbs. (1.09 Kg)

LS7010LOAD SHARE UNIT

INSTALLATION INSTRUCTIONS

The LS7010 Load Sharing Module measures the truepower output of an AC generator and supplies a signalto the generator’s Speed Controller to ensure appropri-ate sharing of the power delivered to the load, whetherthe genset is connected to one or more generator sets inparallel or delivering power to an infinite bus.

Power monitors are incorporated into the LS7010 whichclose contacts at presetable power levels. These con-tacts can be used for signaling the automatic start-up orshut-down of additional engine generator sets. Alter-nately, these contacts may be used for displays or otherdiagnostic warnings.

DESCRIPTION

A single engine generator set supplying power to an iso-lated load may run well isochronously. Thus, under allload conditions, the steady state frequency of the gen-erator is the same. The only deviations from this steadystate frequency are caused momentarily by sudden loadchanges or transients. However, if two engine generatorsets are used to supply power in parallel to a commonload, the two generators are forced to run at exactly thesame speed and in phase with each other. When twogenerators are connected in parallel and supplying a com-mon load, any tendency of one unit to get out of phasewith the other is resisted by the magnetic forces (syn-chronizing torque) within the generators as if they weremechanically connected together.

If each of the two gensets in parallel was controlled byan isochronous governor, each would try to force its speedto be the same as its own reference. Although two iso-chronous governors can be set to nearly the same fre-quency, it is not possible for their references to be ex-actly the same. Under these circumstances the two en-gines must run at some average speed. The first enginewhose governor reference is at a slightly higher frequencywill try to increase its power generation. On the otherhand, the second engine with its governor reference set

slightly below the average speed, will keep decreasingfuel in order to slow down. The net result is that in ashort time, the first engine will be taking all the load itcan and the second engine will be dropping off as muchload as it can until its generator begins acting as a motorwhich will drive its engine.

To force the gensets to carry equal loads, a true powermeasuring device, called a Precise Load Sharing Mod-ule (LS7010), is used with each genset (see Figure 1).

This module takes the voltage and current of each of thethree phases of the generator and develops a DC voltageproportional to the real power supplied by the genset.The power measurements from each paralleled gensetare averaged through the parallel cable connection. EachLoad Sharing Module produces an output signal to it’sSpeed Control Unit which is proportional to the differ-ence between the average power and the power gener-ated by it’s genset. This signal causes the Speed Con-trol Unit to supply more, or less, fuel which increases,or decreases, the power supplied by the genset. Sincethere is as much positive as negative correction, the over-all system remains isochronous. This system is very ac-curate and is independent of actuator and throttle char-acteristics.

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INTRODUCTION

EG LS7010 Inst. 5/99

InputsThe inputs to the load sharing unit are line voltage, linecurrents and battery supply:

AC voltage between 100 volts and 500 volts (measuredfrom line to line) can be used in two selectable ranges:100-240 VAC and 240-500 VAC. The proper voltagerange must be selected using the dip switch located be-hind the round plastic cover on the left side of the case.

Line current inputs are usually from existing currenttransformers ( CT’s) which may be part of the ammetercircuits. Accurate instrument CT’s with secondary rat-ings of 5 amps and a minimum volt-amp rating of 1.25VA should be used. If there is any significant resistancein the CT lines to the load sharing unit, the volt-amprating of the CT may need to be increased accordingly.DC supply voltage (terminal 25 positive and terminal24 negative) range is 12 - 30 VDC.

OutputsParallel cable differential voltage represents real power.Its range is from 0 to approximately 7.5 V for 0 to 5 Achange in CT current and LOAD SENSITIVITY con-trol set fully CW. This voltage can be measured on theLS7000 between test points TP1 and TP2 (TP2 nega-tive) located through the plastic covered adjustment win-dow.

All the load sharing units are connected in parallel viathe parallel cable (terminals 11 and 12). If any voltagedifference between paralleled units exists, a small DCcurrent will flow in the parallel cable. This current willcause the respective speed control units’ references tobe set to a slightly different speed; some raised, somelowered. Since the increases in reference speeds arebalanced by the decreases, the system speed remainsunchanged. Only the power delivered by each gensetwill change in the direction to reduce the paralleling cablecurrent to a minimum. The LOAD SENSITIVITY con-trol can be used to match the generator power output ofeach unit to others.

Parallel Cable OutputThis output is normally connected to the parallel cablesof all other interconnected gensets through auxiliary con-tacts on the genset’s circuit breaker.

Reverse Power MonitorThis circuit (as well as the Forward Power Monitor cir-

cuit) provides 10 Amp, form C, N.O. and N.C. relaycontacts (terminals 27, 26, 28). The relay is energizedwhen generator power is negative. The REV (reversepower monitor) LED lights, indicating reverse power.The reverse power relay trip point can be adjusted viathe REVERSE POWER MONITOR LEVEL adjustment.CW adjustment increases the amount of reverse powerneeded to trip the relay. The adjustment range is ap-proximately 2% to 20% assuming 5A of CT current cor-responds to 100% load.

An adjustable time delay is built into the unit. Clock-wise adjustment increases time delay. The circuit canoperate in latching or unlatching mode. The mode isselected by setting the REV RELAY internal switch lo-cated on the right side of the adjustment window. Inunlatching mode the circuit automatically resets whenreversed power drops below set level. In LATCH mode,when reverse power condition occurs, the circuit willtrip and latch.

A switch (normally closed) for the reverse power moni-tor circuit may be connected between terminals 38 and39 to manually reset the latched monitor after a reversepower condition has been cleared. Reset by openingthis switch.

When the normally closed reverse power reset switchis not used, a jumper must be installed across termi-nals 38 and 39 otherwise the monitor circuit will notoperate.

Forward Power MonitorThe forward power monitor 10 amp form C relay, pro-vides contacts, (terminals 29, 30, 31). It has two trippoints set by POWER MONITORS - FORWARD/ONand FORWARD/OFF adjustments. The relay is ener-gized when power is increasing and exceeds the levelset by the ON adjustment. The relay is de-energizedwhen power falls below the level set by the OFF adjust-ment. The ON point can be adjusted from 20 to 100%load. Adjusting the FORWARD POWER MONITORS/ON control CW will increase the trip point (relay ener-gized) from 20% to 100% load. Adjusting the FOR-WARD POWER MONITORS/OFF control CW will in-crease the trip point (relay de-energized) from 0% to 80%load. A time delay circuit is built in similar to the delayin the reverse power monitor delay.

The forward power monitor trip points can be influenced

LOAD SHARING

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externally through terminal 23. Connecting the terminalForward Power Monitor (continued)to GND (terminal 24) will lower the trip points byapproximately 20 %. External voltage signal can alsobe applied to terminal 23 to influence the trip points.

External Power MeterA DC voltage signal proportional to generator real poweris available on terminals 33 (+) and 34 (-). The signalcan be calibrated with the EXTERNAL POWERMETER CALIBRATION adjustment. The maximumsignal range for the adjustment in full CW position and5 Amps CT current is approximately -2 to +5.5 V.

Power Bar GraphThis displays the generator power level. The displaycan be calibrated with the DISPLAY CALIBRATIONadjustment. Adjusting clockwise increases the sensitiv-ity of the display.

Power Factor IndicatorA group of six LED (two for each phase) indicators areprovided on the left side of the case marked PHASEFORWARD-REVERSE. If only the green LED lights,there is no shift between voltage and current in that phase.The red LED’s brightness will increase with increasingphase angle displacement between voltage and currentin each phase. For 90 degree displacement both red andgreen LED’s will have equal brightness. For 180 degreeonly the red LED will light.

The indicator can be also used for checking phasing ofthe current transformers as described in the Installationsection following.

Output To Speed ControllerTerminal 13 is used to send a signal to AMBAC speedcontrollers. Its neutral level is 5 V. Terminals 19 -22 areused when LS7010 is working with Cummins EFC speedcontrollers (see Figures 2 and 3 for details).

Reversed Output ModeThis is obtained by moving the switch marked OUTPUTREVERSED/NORMAL located on the right side of theadjustment window to REVERSED position. The redLED located on the right side of the switch (visible inthe adjustment window) will then light up.

This mode is used when the LS7010 is monitoring themains in peak shaving application. In such case, if moni-tored power supplied by the mains tends to be too high,the speed controller(s) is signaled to increase generatedpower.

In normal mode when measured power tends to be toohigh, the speed controller is signaled to decrease gener-ated power.

All units are factory set in normal output mode. Makesure the switch is in the right position for your specificapplication.

Load AnticipationA load anticipation signal is included in the module tominimize speed transients. An internal LOADANTICIPATION control is provided to adjust thesensitivity of this function. CW rotation of the adjustmentincreases sensitivity.

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Preset the LOAD SENSITIVITY control on each loadsharing unit to the full CW position. Set the LOADANTICIPATION adjustment fully CCW. Apply resis-tive load to the generator (load bank). With a DC volt-meter, measure the voltage across test points TP1 (+)and TP2 (-) with a load applied to the generator. A volt-

INSTALLATION

ADJUSTMENTS

age of about +7.5 volts will represent full load with 5amps CT input. Proper current transformer phasing mustbe observed. Observe the group of six FORWARD andREVERSE LED’s on the left side of the case. All threegreen FORWARD LED’s should light and the red RE-VERSE LED’s should be dark. Only a red LED lightedon any of the phase indicators indicates reversed con-nection of the current transformer. Both red and greenLED’s remaining dark on any of the phase indicatorsindicates a missing connection. Also, both green andred LED’s for a phase will light if the current transformeris connected to the wrong line. Make sure power is offbefore making corrections.Once the proper CT phasing has been verified, the gen-erator sets may then be synchronized manually with thespeed trim control or with the automatic synchronizer(e.g.: AMBAC’s SY6000). Once synchronized, the gen-erator sets can be paralleled.

The LS7010 Precise Load Sharing Module is shownwired into a typical 2 Genset System with AMBAC’sSpeed Controller and Synchronizer in Figure 2. Figure3 shows a 2 Genset System with a Cummins or BarberColman Speed Controller.

Terminals 5 through 10 are part of the CT circuits andrequire currents up to 5 amps to operate properly. If theresistance of the cables connecting the CT’s to the LoadShare Module have 0.1 ohms resistance, this will raisethe demand on the CT’s VA rating by 200%, based on0.05 ohm sensing resistors within the module. Thus itis recommended that the resistance of these lead wiresbe held reasonably low. The parallel cable operates withlow voltage and low current so almost any shielded, 2

conductor cables will suffice. It is recommended thatsome care be taken not to allow leakage of current be-tween the parallel cables or from the parallel cable toground or other circuits. Such leakage can cause un-wanted droop.

The connections to terminals 13, 19 - 22 (speed control-ler) may require a shielded cable if this is not a directconnection of short length.

The wiring to the generator must be of appropriate sizeto carry the voltage and current to the load sharing units.The voltage sensing connections 1 through 4 require verylow currents (less than 10 mA), so wire size and qualityconsistent with good mechanical installation is recom-mended.

CAUTION:THE ENGINE SHOULD BE EQUIPPED WITHAN INDEPENDENT OVERSPEED SHUTDOWNMECHANISM TO PREVENT RUNAWAYWHICH CAN CAUSE EQUIPMENT DAMAGEOR PERSONNEL INJURY.

CAUTION:HIGH VOLTAGE PRESENT ON TERMINALS1-4. NEVER OPEN CIRCUIT CT’s ON TERMI-NALS 5-10 AS HIGH VOLTAGE WILL THENBE PRESENT.

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The installer is responsible to insure that the in-stallation is in conformance with all applicablelocal codes and regulations. Consistent with theserequirements, a solid electrical connection shouldbe provided between the metal case. The LoadSharing Module and “earth ground” to preventshock hazard to service personnel. A good groundshould also minimize the effects of electrical noiseon the speed control system.

One of the mounting screw locations on the LoadShare Module is clear of paint (bare metal). A 20AWG or larger grounding wire with a ring tongueterminal should be solidly fastened to the case atthis location by the mounting screw and the otherend of the wire should be solidly connected to agood “earth ground”. Ensure that the metal is cleanand free of corrosion, if necessary, and apply acoating of grease or lacquer to protect the bond.

NOTE

Instability, when the units are paralleled, mayoccasionally result. The instability can be caused by theLOAD SENSITIVITY control of any of the load sharingmodules being set too high. Turn the LOADSENSITIVITY controls on all the modules CCWproportionately until stability is restored. The systemshould stabilize with the controls no more than 75%CCW.

With the system at no load, adjust each generator set forzero real power output reading on the generator set watt-meter with the electric governor speed trim adjustment.Then adjust the voltage regulators to trim the reactivecurrent on the generator set ammeter to zero. Ideally allsix FORWARD and REVERSE LED’s should now bedark.

Load can now be applied to the system. If instabilityoccurs, see “Troubleshooting”.

Load SharingOnce the system has load applied, it is important thateach engine share the system load proportionally. Checkthe power output of each generator set that is reflectedby each generator set wattmeter. The generator set car-rying the least proportion of the load can be adjusted byturning the appropriate LOAD SENSITIVITY adjust-ment CCW until its share of the load has been pickedup.

Load AnticipationThe load sharing units have a load anticipation circuit toimprove load transient response. The LOAD ANTICI-PATION adjustment is factory set at zero sensitivity (fullCCW). The LOAD ANTICIPATION should be adjustedwhile the engines are in parallel. Carefully advance thecontrol CW as far as possible while occasionally pokingthe throttle or changing load. Instability or overshootmay result if the control is advanced too far; in which

case, turn it CCW until stability is restored.

Reverse PowerTurn the REVERSE POWER MONITOR LEVELcontrol fully CW, then supply the desired real or simu-lated reverse power load to set the trip level (2% to20% full load). Simulated reverse power can beachieved by reversing connections to each CT tempo-rarily. Then slowly turn the control CCW until theREV (reverse power) LED lights. Once the reversepower is set, re-instate the proper CT connections. CWrotation increases the reverse power trip set point. Adelay of this function may be necessary in some casesand the REVERSE POWER MONITOR DELAY con-trol is provided for this purpose. Turning it CW in-creases the delay.

Forward PowerTurn the FORWARD POWER MONITOR ON con-trol fully CW and turn the FORWARD POWERMONITOR OFF control fully CCW. Supply the de-sired load to set the ON forward power monitor. Turnthe ON control CCW until the FWD (forward power)LED lights. CCW rotation decreases the ON forwardpower trip set point. Reduce the load to the desiredlevel to set the OFF forward power monitor. Turn theFORWARD POWER MONITOR OFF control slowlyCW until the FWD (forward power) LED goes out.CW rotation increases the OFF forward power setpoint.

TROUBLESHOOTING

If instability is still present, the gain adjustment on thespeed control unit may be reduced slightly or it is pos-sible that the voltage regulator is marginally stable andadjustment of the voltage regulator is required. Refer tothe voltage regulator manufacturer’s instructions foradjusting the regulator for parallel operation.

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ADJUSTMENTS Continued

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Figure 1. Block Diagram - Typical Paralleled Genset Application

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Figure 2. Wiring Diagram to an AMBAC Speed Controller and Synchronizer

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Figure 3. Wiring Diagram to a Barber Colman or Cummins Speed Control and AMBAC Synchronizer