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The current limiting potentiometer (4) is used to select the starting current recommended for vari-
ous aircraft. The current limiting setting is continuously adjustable from 300 to 1600 amperes.
(5) Switches
The contactor control switch (11, Figure 4) is a three-position toggle switch used to close and
open the output load contactor. The top CLOSE position is spring-loaded and is held momentarily
until the contactor closed light (12) glows, then it is released to the center ON position. In this posi-
tion the switch provides holding current to the load contactor to keep it closed. Protective devices
in the load contactor circuit provide protection against overvoltage by opening the load contactor if
that condition occurs. In the bottom OFF position, the contactor is opened. The push-to-build-up-
voltage switch (10) is a momentary contact pushbutton switch which flashes the generator fields
with 12 volt engine circuit when flashing the fields.
The panel lights switch (8, Figure 4) turns the lights (7) on and off. The engine start switch (17) is
a momentary contact pushbutton which closes the starter relay (8, Figure 3) and cranks the en-
gine. This switch is operable only when the engine (ignition) switch (19) is held in its top spring-
loaded START position.
The engine (ignition) switch (19), when released from its top START position after the engine
starts, will return to center RUN position. The engine ON light (14) will glow as long as the switch
is in RUN position. In the bottom STOP position, the switch will stop the engine and the light (14)
will go out.
Refer to Figure 4. The speed control switch, (13) is a two position toggle switch wired to an idling
device on the engine. In the IDLE position, used for starting, the engine speed is controlled ap-
proximately 900-1000 RPM. In the Rated RPM position, engine speed is controlled to approxi-
mately 2600 RPM.
(6) Fuses
Three cartridge-type fuses protect the engine ignition circuit, the panel lights circuit, and the volt-
age regulator. The engine circuit fuse (16, Figure 4) is rated at 20 amperes, the panel lights fuse
(9) at 10 amperes, and the voltage regulator fuse (4, Fig. 5) at 10 amperes.
(7) Voltage regulator
Refer to Figure 5. The voltage regulator (1) is a solid-state device which regulates the 28.5 volt
DC generator output after the voltage is built up.
(8) Overvoltage module
The overvoltage relay (2) is a solid-state protective device on a printed circuit board. A normally
closed relay in the circuit is wired into the load contactor coil circuit. An overvoltage condition
causes the relay contacts to open, which in turn prevents the contactor from closing, or opens the
load contactor and discontinues the power delivery. The overvoltage module is adjusted to to trip
at 32 to 34 volts DC in 2 to 10 seconds.
(9) Resistor and diode assembly
This network which is mounted on a terminal strip behind the control panel, protects the overvol-
tage module against reverse current when the generator is delivering power.
May 20/89
OM-2049
1-1
Page 9
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Troubleshooting
