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PRECISE LOAD SHARING MODULE - Ambac ... principal load, a single generator. Load Sharing The load...

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    Engine Governing Systems

    Page 1

    ENGINE GOVERNING SYSTEMS

    IN E R N A TIO N A L

    LS 671A SECTION EG 70-10

    PRECISE LOAD SHARING MODULE

    LS 671A Section EG 70-10

    PRECISE LOAD SHARING MODULE

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    Engine Governing Systems

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    Engine Governing Systems

    Page 1

    ENGINE GOVERNING SYSTEMS

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

    "" LS 671A SECTION EG 70-10

    INTRODUCTION The LS 671A Precise Load Sharing Module is an accessory outputs, a multiple arrangement of generator sets can be device used in conjunction with the AMBAC International connected in parallel to share load equally. The module Engine Governing system. It measures the true power can also be used to control the power output of one or output 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

    SPECIFICATIONS 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 ..................................... HZ LOW RANGE ItIGIt RANGE

    Min Max Min Max

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

    50 140 208 280 417 60 170 260 340 500

    400 170 260 340 500

    *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.

    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 *60 50 60 400

    LOW RANGE HIGH RANGE Min 70 85 140 170 170

    Min 140 170 280 340 340

    Max 104 130 208 260 260

    Max 208 260 417 500 500

    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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    Engine Governing Systems

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    Engine Governing Systems

    ELECTRIC GOVERNOR

    CT 1

    CT 2

    CT 3

    LOAD SHARING SENSITIVITY

    DROOP LOAD ANTIC

    ADJUST ADJUST

    PARALLEL CABLEJUMP 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 POINTS 185mm 7.2812

    13mm 0.5”

    10mm 0.375”

    52mm 2.0625”

    141mm 5.5625”

    152mm 6”

    8mm 0.3125” TYP.207mm

    8.1562” 7mm

    0.2656” DIA. -4 HOLES

    416

    208

    1 2 3 + -

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    Engine Governing Systems

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    Engine Governing 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 Sharing The 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 us

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