SR 4 GENERATOR
SYSTEMS OPERATION
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 MODULE
C68
SERIES BOOST CAPACITOR
E5
SERIES BOOST HEAT SINK
T3
VOLTAGE SENSING TRANSFORMER
If 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.
NOTE
For current transformer connection
of
machines
not
shown,
make
contact with Service Engineering;
Caterpillar Tractor Co.
CURRENT TRANSFORMER T2
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