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section 3
DescRiption & coMponents
with a 62 Hz AC frequency (62 Hz equals 3720 rpm).
At the stated no-load frequency, adjust to obtain a
line-to-line AC voltage of about 252 volts.
CIRCUIT BREAKERS:
Each individual outlet on the generator is protected by
a circuit breaker to prevent overload.
ROTOR RESIdUAL MAgNETISM
The generator revolving field (rotor) may be consid-
ered to be a permanent magnet. Some "residual"
magnetism is always present in the rotor. This residu-
al magnetism is sufficient to induce a voltage into the
stator AC power windings that is approximately 2-12
volts AC.
FIELd bOOST CIRCUIT
When the engine is cranked during start-up, the
START/STOP RELAY (SSR) will be energized. The
normally open contacts of the SSR will close and Wire
15 will supply 12 VDC to Wire 14. Connected to Wire
14 is a resistor (R1) and a diode (D1). The resistor
will limit current flow, and the diode will block Voltage
Regulator DC output. Once through the resistor and
diode it becomes Wire 4, and Wire 4 then connects
to the positive brush. 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.
Notice that field boost current is always available dur-
ing cranking and running, this is because the SSR is
energized the whole time. The diode (D1) prevents or
blocks the Voltage Regulators higher DC output from
reaching the Wire 14 run circuit.
Field boost voltage is reduced from that of battery
voltage by the resistor (R1), and when read with a DC
voltmeter will be approximately 9 or 10 volts DC.
OPERATION
STARTUP:
When the engine is started, residual plus field boost
magnetism from the rotor induces a voltage into (a)
the stator AC power windings, (b) the stator excitation
or DPE windings, (c) the stator battery charge wind-
ings. In an "on-speed" (engine cranking) condition,
residual plus field boost magnetism are capable of
creating approximately one-half the unit's rated volt-
age.
ON-SPEED OPERATION:
As the engine accelerates, the voltage that is induced
into the stator windings increases rapidly, due to the
increasing speed at which the rotor operates.
Page 12
FIELD EXCITATION:
An AC voltage is induced into the stator excitation
(DPE) windings. The DPE winding circuit is completed
to the Voltage Regulator, via Wire 2, Excitation Circuit
Breaker, Wire 162, and Wire 6. Unregulated alternat-
ing current can flow from the winding to the regulator.
The Voltage Regulator "senses" AC power winding
output voltage and frequency via stator Wires 11S and
44S.
The regulator changes the AC from the excitation
winding to DC. In addition, based on the Wires 11S
and 44S sensing signals, it regulates the flow of direct
current to the rotor.
The rectified and regulated current flow from the regu-
lator is delivered to the rotor windings, via Wire 4, and
the positive brush and slip ring. This excitation current
flows through the rotor windings and is directed to
ground through the negative (-) slip ring and brush,
and Wire 0.
The greater the current flow through the rotor wind-
ings, the more concentrated the lines of flux around
the rotor become.
The more concentrated the lines of flux around the
rotor that cut across the stationary stator windings,
the greater the voltage that is induced into the stator
windings.
Initially, the AC power winding voltage sensed by the
regulator is low. The regulator reacts by increasing
the flow of excitation current to the rotor until volt-
age increases to a desired level. The regulator then
maintains the desired voltage. For example, if voltage
exceeds the desired level, the regulator will decrease
the flow of excitation current. Conversely, if voltage
drops below the desired level, the regulator responds
by increasing the flow of excitation current.
AC POWER WINDING OUTPUT:
A regulated voltage is induced into the stator AC
power windings. When electrical loads are connected
across the AC power windings to complete the cir-
cuit, current can flow in the circuit. The regulated AC
power winding output voltage will be in direct propor-
tion to the AC frequency. For example, on units rated
120/240 volts at 60 Hz, the regulator will try to main-
tain 240 volts (line-to-line) at 60 Hz. This type of regu-
lation system provides greatly improved motor starting
capability over other types of systems.
BATTERY CHARGE WINDING OUTPUT:
A voltage is induced into the battery charge winding.
Output from these windings is delivered to a Battery
Charge Rectifier (BCR2), via Wires 55A, 66A and
77A. The resulting direct current from the BCR is
delivered to the unit battery, via Wire 15, a 10 amp
fuse, and Wire 13. This output is used to maintain bat-
tery state of charge during operation.
10 AMP BATTERY CHARGE WINDING OUTPUT:
A voltage is induced into the battery charge winding.
Output from these windings is delivered to a Battery
Charge Rectifier (BCR1), via Wires 55, 66 and 77.
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Troubleshooting
