HOUSING 3P0319 - Caterpillar

Series Boost Attachment
Series boost lets SR 4 generators stay on the line, for approximately 10 seconds, when there is a short in the generating or load circuits. This gives circuit breakers a chance to trip in sequence. When circuit breakers trip in sequence, there is less chance for a loss of power to all of the electrical system.The series boost panel group has a control module A3, voltage sensing transformer T3 and series boost heat sink E5. Current transformer T2 is external to the panel group.Voltage sensing transformer T3 gets power from the same terminals on the regulator terminal strip as exciter field L3 (terminals 24 and 22 on 580 frame generators and terminals 24 and 26 on all others). Voltage sensing transformer T3 gives power to control module A3. The electrical action of control module A3 causes a gate signal through wire 34 to the triac on series boost heat sink E5. The triac short circuits current transformer T2. This prevents any series boost effect during normal operation.
SERIES BOOST ASSEMBLY A3 CONTROL MODULEC68 SERIES BOOST CAPACITORE5 SERIES BOOST HEAT SINKT3 VOLTAGE SENSING TRANSFORMERIf there is a short circuit that causes the voltage to voltage 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 the bridge rectifier on heat sink E5, be rectified and flow through wire 9 to exciter field L3. This field current will be enough to give at least three times full load current into a short circuit. After approximately 10 seconds electrical action of control module A3 will again cause a gate signal through wire 34 to the triac on series boost heat sink E5. The triac will short circuit current transformer T2. Current flow to exciter field will be zero until the short circuit is corrected.Series boost connections are not the same for all generator sets. Make reference to Fig. 1 or Fig. 2 for series boost to regulator connection. For series boost current transformer T2 connection, make reference to Fig. 3, Fig. 4, Fig. 5 or Fig. 6. For current transformer connection of machines not shown, make contact with Service Engineering; Caterpillar Tractor Co.
CURRENT TRANSFORMER T2
FIG. 1 SR 4 GENERATOR WITH SERIES BOOST
[Includes: 447, 448 & 449 frame (layer wound rotor - 208 V only); and all other frames (random and layer wound rotors) except 580 frame and 447, 448, and 449 frame (with layer wound rotor).]
FIG. 2 SR 4 GENERATOR WITH SERIES BOOST
[Includes: 580 frame and 447, 448 & 449 frames (with layer wound rotor) except 447, 448 & 449 frames with layer wound rotor - 208 V.]
FIG. 3 TRANSFORMER CONNECTIONS DIAGRAM 1. Generator.2. Transformer (in series boost).3. Load line leads (generator).4. Load line leads (tranformer).5. Series boost terminal strip.6. Heat sink (for connection to terminal strip, make reference to secondary transformer connections chart).7. Wire from excitation field.8. Terminal strip on generator regulator.
LINE LEAD CONNECTIONS FOR SR 4 GENERATORS IN FIG. 3
FIG.