SR 4 GENERATORSYSTEMS OPERATIONSERIES BOOST ATTACHMENTSeries boost lets SR 4 generators stay on the line, forapproximately 10 seconds, when there is a short in thegenerating or load circuits. This gives circuit breakers achance to trip in sequence. When circuit breakers trip insequence, there is less chance for a loss of power to allof the electrical system.The series boost panel group has a control module A3.voltage sensing transformer T3 and series boost heatsink E5. Current transformer T2 is external to the panelgroup.Voltage sensing transformer T3 gets power from thesame terminals on the regulator terminal strip as exciterfield L3 (terminals 24 and 22 on 580 frame generatorsand terminals 24 and 26 on all others). Voltage sensingtransformer T3 gives power to control module A3. Theelectrical action of control module A3 causes a gatesignal through wire 34 to the triac on series boost heatsink E5. The triac short circuits current transformer T2.This prevents any series boost effect during normaloperation.SERIES BOOST ASSEMBLYA3CONTROL MODULEC68SERIES BOOST CAPACITORE5SERIES BOOST HEAT SINKT3VOLTAGE SENSING TRANSFORMERIf there is a short circuit that causes the voltage tovoltage sensing transformer T3 to drop to a low value,control module A3 will stop the gate signal to the triac.Current from current transformer T2, will go through thebridge rectifier on heat sink E5. be rectified and flowthrough wire 9 to exciter field L3. This field current willbe enough to give at least three times full load currentinto a short circuit. After approximately 10 secondselectrical action of control module A3 will again cause agate signal through wire 34 to the triac on series boostheat sink E5. The triac will short circuit currenttransformer T2. Current flow to exciter field will be zerountil the short circuit is corrected.Series boost connections are not the same for allgenerator sets. Make reference to Fig. 1 or Fig. 2 forseries boost to regulator connection. For series boostcurrent transformer T2 connection, make reference toFig. 3, Fig. 4, Fig. 5 or Fig. 6.NOTEFor current transformer connectionof machines not shown, makecontact with Service Engineering;Caterpillar Tractor Co.CURRENT TRANSFORMER T243
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