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Section 1
GENERATOR FUNDAMENTALS
FIELD BOOST
When the engine is cranked during startup, the
engine's starter contactor is energized closed. Battery
current is then delivered to the starter motor and the
engine cranks.
Closure of the starter contactor contacts also delivers
battery voltage to Pin 13 of an Engine Controller cir-
cuit board. The battery current flows through a 47
ohm, 2 watt resistor and a field boost diode, then to
the Rotor via brushes and slip rings. This is called
"Field Boost" current.
Field boost current is delivered to the Rotor only while
the engine is cranking. The effect is to "flash the field"
every time the engine is cranked. Field boost current
helps ensure that sufficient "pickup" voltage is avail-
able on every startup to turn the Voltage Regulator on
and build AC output voltage.
NOTE: Loss of the Field Boost function may or
may not result in loss of AC power winding out-
put. If Rotor residual magnetism alone is suffi-
cient to turn the Regulator on loss of Field Boost
may go unnoticed. However, If residual magnet-
ism alone Is not enough to turn the Regulator on,
loss of the Field Boost function will result In loss
of AC power winding output to the load. The AC
output voltage will then drop to a value commen-
surate with the Rotor's residual magnetism (about
7-12 VAC).
Page 6
GENERATOR AC CONNECTION SYSTEM
120 VAC OUTPUT:
The Stator AC power winding consists of two wind-
ings connected in parallel, with each winding capable
of supplying 120 volts AC.
POWER WINDING
44
22P
WHITE
GREEN
T2
Figure 1-8. – Power Winding Output
33
11P
CB1
T1
BLACK
120V 30A
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Troubleshooting
