ARMY TM 9-6115-644-24
AIR FORCE TO 35C2-3-446-12
MARINE CORPS TM 09249A/09246A-24/2
1-12-7-2 Power created by the generator is supplied through the current transformer, AC voltage reconnection terminal
board, and AC circuit interrupter relay to the load output terminals. The AC voltage reconnection terminal board allows
configuration of the generator set for 120/208 volt connections or 240/41 6 volt connections. The AC CIRCUIT INTER-
RUPTER switch doses and opens the AC circuit interrupter relay. This enables or interrupts the power flow between the
AC voltage reconnection terminal board and the load output terminals. The voltage regulation system (refer to paragraph
1-12-10) senses generator output voltage and provides a control signal to the generator exciter to maintain the desired
generator output voltage. Generator output frequency is controlled by the governor control system (refer to paragraph
1-12-9) and is read on the frequency meter (HERTZ). The current transformer provides a reduced current signal to the
kilowatt transducer and ammeter (PERCENT RATED CURRENT). The kilowatt transducer and kilowattmeter (PERCENT
POWER) provide an indication of the power being used by the load. The ammeter (PERCENT RATED CURRENT) indi-
cates the percent of rated current being supplied to the load. The position of the AM-VM transfer switch selects the output
load terminals from which current and voltage is measured. The AC circuit interrupter relay will open and disconnect the
load whenever any of the following faults occur: reverse power, undervoltage, overload, or short circuit.
1-12-7-3 The AC generator also provides 120 VAC power to the CONVENIENCE RECEPTACLE through the GROUND
FAULT CIRCUIT INTERRUPTER.
1-12-8 Generator Set Controls.
1-12-8-1 Engine Starting System.
1-12-8-1-1 Engine starting is accomplished primarily with two 12-volt batteries, connected in series to provide 24 VDC
power, and a starter (FIGURE 1-9). The starter includes a cranking motor and a solenoid. To permit engine starting, the
DC CONTROL POWER circuit breaker must be pushed in, the DEAD CRANK switch must be in the NORMAL position
and the BATTLE SHORT switch must be in the OFF position. In addition, any ENGINE SHUTDOWN fault previously regis-
tered on the malfunction indicator panel must have been corrected and the malfunction indicator panel must have been
When the MASTER SWITCH is then placed in the START position, the starting circuits supply 24 VDC power to the starter.
As the engine accelerates to approximately 900 rpm, the starling circuits disconnect power from the starter.
1-12-8-1-2 When the MASTER SWITCH is first moved to the START position, the various instrument and control circuits
are energized. The Engine Starting System includes two control aircuits. One starting control circuit energizes the start
relay through closed switch contacts of the engine fault relay and the BATTLE SHORT switch. The other starting control
circuit energizes the cranking relay coil through closed contacts of the crank disconnect switch and the start relay. (The
crank disconnect switch is an integral part of the electronic governor control.) With the cranking relay energized, power
passes from the batteries through closed contacts of the Cranking relay to energize the starter solenoid. With the starter
solenoid energized, power passes from the starter solenoid to the cranking motor. The cranking motor then cranks the
engine. Engine speed is sensed by the magnetic pickup which sends a signal to the electronic governor control. As the
engine accelerates to approximately 900 rpm, the signal from the magnetic pickup causes the crank disconnect switch
to open one set of contacts and close another set of contacts. The open contacts break the circuit to the cranking relay
and stop engine cranking. The closed contacts cause the field flash relay to be energized. When the MASTER SWITCH
is moved to one of the two RUN positions, both starting control circuits are deenergized. The other generator set control
and instrument circuits remain energized.
1-12-8-1-3 The engine may be cranked without starting by use of the DEAD CRANK switch. With the DEAD CRANK
switch in the CRANK position, the cranking relay coil is energized to initiate engine cranking without energizing any other
starting or control functions.
1-12-8-14 The generator set can be started without batteries by connecting an external 24 VDC power source to the
NATO SLAVE RECEPTACLE. The generator set can also supply starting power to another set through the NATO SLAVE
1-12-8-1-5 The batteries are charged by the battery charging alternator that is belt driven by the engine. The BATTERY
CHARGE ammeter indicates the charge/discharge rate of the batteries, from -10 Amps to +20 Amps. A shunt provides
a DC voltage signal, which is directly proportional to the actual battery current flow, to the BATTERY CHARGE ammeter.
Normal operating indication on the BATTERY CHARGE ammeter depends on the state of the charge in the batteries. A
low charge, which may exist immediately after engine starting, will cause a high reading (needle moves toward CHARGE
area). When the charge in the batteries has been restored, the indicator moves near zero. The battery charging system
is protected from reverse polarity in the battery connections by a fuse and diode.