ARMY TM 9-6115-642-24
AIR FORCE TO 35C2-3-455-12
MARINE CORPS TM 09247A/09248A-24/2
SECTION Ill. PRINCIPLES OF OPERATION
with the systems, and the location and description of major components.
PRINCIPLES OF OPERATION.
1-12.1 Fault System.
1-12.1.1 The Fault System (FIGURE l-2) protects the generator set and any connected Ioad against the potential faults
described below and provides an indication of any incurred fault. The following summary of the Fault System will assist
in understanding the operation of other generator set systems. Additional details relating to specific protection devices
are provided in the descriptions of the respective systems.
1-12.1.2 The Fault System consists of the malfunction indicator, Iow fuel Ievel float switch, fuel float switch module, fuel
level relay, low oil pressure switch, oil pressure relay, coolant high temperature switch, overvoltage relay, overload/short
circuit relay, engine fault relay, and BATTLE SHORT switch. In addition to the fault indicator lamps, the malfunction indica-
1-12.1.3 Activation of any one of the following protection devices will cause three events to occur. The AC circuit inter-
rupter relay holding circuit will be deenergized causing the AC circuit interrupter relay to open; the generator set engine
will be shut down; and a fault indicator lamp will be illuminated to show which malfunction occurred.
1-12.1 .3.1 Coolant High Temperature Switch. This device will activate when the engine coolant leaving the engine ex-
ceeds 225 ± 5°F (107 ± 3°C).
1-12.1 .3.2 Low Oil Pressure Switch. This device activates when the engine lubrication oil pressure falls below 15 ± 3
psi (103.4 ± 20.7 kPa).
time of the set at rated load is four minutes.
1-12.1 .3.4 Overvoltage Relay. This device will activate when the 120-volt generator coil winding has risen to and re-
mained at any value greater than 153 ± 3 volts.
1-12.1.4 Fuel Float Switch Module. This device prevents inadvertent engine shutdown by providing a one second delay
after actuation of the low fuel level float switch.
1-12.1.5 Activation of any of the following electrical protection devices will cause two events to occur. The AC circuit
interrupter relay will open and a fault indicator lamp will illuminate to indicate which fault occurred.
1-12.1 .5.1 Short Circuit Relay. This device will activate when the set output current in any phase exceeds 425 ±25 per-
cent of the rated value.
1-12.1 .5.2 Overload Relay. This device will operate when the load current in any phase exceeds 110 percent of rated
1-12.1.6 Although it is possible for more than one fault to occur at onetime during operation, only the first fault to occur
will be displayed by the malfunction indicator. The activated indicator lamp circuit remains illuminated until the malfunction
indicator is reset. The lamp will be off with the MASTER SWITCH in the OFF position and will be reilluminated when the
MASTER SWITCH is turned to one of the RUN positions. Resetting a fault indication is done in two steps. First push the
PUSH TEST & RESET LAMPS switch located on the malfunction indicator. Then move the MASTER SWITCH to the OFF
position. The generator set cannot be cranked unless both actions are completed. The indicated fault must be corrected
before any attempt is made to restart the generator set or close the AC circuit interrupter relay.
1-12.1.7 After the generator set engine has been started, the BATTLE SHORT switch can be used to override all of the
potential faults except short circuit.