ARMY TM 9-6115-641-24
AIR FORCE TO 35C2-3-456-12
1-12-8-1-4. 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. Generator
set control system power is also supplied by the battery charging alternator. The BATTERY CHARGE ammeter indicates
the charge rate of the batteries, from -10 to +20 amps. The ammeter is connected to a shunt which provides a DC voltage
signal, which is directly proportional to the battery current flow, to the BATTERY CHARGE ammeter. Normal operating
indication depends on the state of charge in the batteries. A low charge which can 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 (0). The battery charging system is protected from a reverse polarity when connecting the
batteries by a fuse and diode.
1-12-8-2. Field Flash. When the engine reaches sufficient speed (900 rpm), the magnetic pickup causes a setofmntacts
in the crank disconnect switch to open and de-energize the crank disconnect relay. A set of contacts in the crank discon-
nect relay then doses and energizes the Field Flash circuit through dosed contacts of the field flash relay (refer to
Figure 1-9). This provides current to the AC generator exciter field windings which sets up an electromagnetic field. The
field current is necessary for the set to generate sufficient voltage for the voltage regulator (refer to Figure 1-11) to begin
controlling the output voltage of the generator set. The Field Flash circuit is maintained until the MASTER SWITCH is
released from the START position.
1-12-8-3. Operation. Placing the MASTER SWITCH in the PRIME & RUN or PRIME RUN AUX positions keeps the fuel
solenoid energized, and fuel will be supplied to the engine as long as no fault condition exists. During operation, the opera-
tor should periodically check the sets instruments to ensure they are reading in the normal operating ranges. The VOLT-
AGE and FREQUENCY adjust controls are adjusted as required to maintain the desired frequency and voltage output.
1-12-8-4. Applying the Load. The load is applied by dosing the AC CIRCUIT INTERRUPTER switch (refer to
Figure 1-8). This is a momentary contact switch that returns to the neutral, or center position. The AC circuit interrupter
relay is energized by this momentary contact, and a holding circuit keeps it dosed, bringing the load on line.
1-12-8-5-1. The AC circuit interrupter relay is disengaged by placing the AC CIRCUIT INTERRUPTER switch in the
OPEN position. This is a momentary contact switch which will break the AC circuit interrupter relay holding circuit and
then return to the neutral, or center position, disconnecting the load from the line.
1-12-8-5-2. When the MASTER SWITCH is placed in the OFF position, all power is removed from the control circuit
and the engine will stop.
1-12-6-5-3. The EMERGENCY STOP switch will remove power from the control circuit by energizing the engine fault
relay. This will cause the engine to shut down. The EMERGENCY STOP switch is not to be used as an alternative for
routine shutdown procedures. When the generator set is stopped using the EMERGENCY STOP switch, some circuits
remain energized causing a drain on the batteries until the MASTER SWITCH is placed in the OFF position.
1-12-9. Governor Control System.
1-12-9-1. The Governor Control System (FIGURE 1-10) includes the FREQUENCY ADJUST control, mechanical en-
gine governor, engine fuel pump rack and fuel solenoid.
1-12-9-2. The mechanical engine governor is housed under the engine gear cover and moves the fuel pump rack, chang-
ing fuel delivery of the injection pumps in proportion to engine load. The governor is a flyweight type, with the weights
mounted on the engine camshaft gear. The force of the flyweights is transferred through a thrust sleeve and collar to the
governor lever, and balanced against the tension of the governor spring, which is stretched between the governor lever
and the speed adjustment lever. Engine speed and generator output frequency are increased by increasing the tension
on the main governor spring. Droop is adjusted by varying the location of the governor springs mounting to the governor
lever, effectively varying the strength of the spring.
1-12-9-3. The governor uses one Iever for fuel shutoff and the other for speed adjustment. The shutoff lever is operated
by the fuel solenoid in an energize-to-run configuration (fail safe). The speed adjustment lever is moved by a vernier
control cable from the FREQUENCY ADJUST control of the set and provides an adjustment range of ± 3 percent of rated