ARMY TM 9-6115-643-24
AIR FORCE TO 35C2-3-445-22
Section Ill. PRINCIPLES OF OPERATION
This section contains functional descriptions of the generator set and explains how the controls and indicators inter-
act with the systems, and the location and description of major components.
1.12 PRINCIPLES OF OPERATION.
1.12.1 Fault System.
The Fault System (FIGURE 1-2) protects the generator set and any connected load 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 the other generator set systems. Additional details relating to specific protection
devices are also provided in the descriptions of the respective systems.
The Fault System consists of the malfunction indicator, low fuel level float switch, fuel float switch module,
fuel level relay, low oil pressure switch, coolant high temperature switch, overvoltage relay, overload/short circuit relay,
overspeed switch, overspeed relay, OVERSPEED RESET switch, undervoltage relay, reverse power relay, engine fault
relay, electrical fault relay, and BATTLE SHORT switch. In addition to the fault indicator lamps, the malfunction indicator
includes the PUSH TEST & RESET LAMPS switch which when depressed, illuminates all the lamps and resets any fault
Activation of any one of the following protection devices will cause three events to occur. The AC circuit inter-
rupter relay will open; the generator set engine will be shut down; and a fault indicator lamp will be illuminated to show
which malfunction occurred.
Coolant High Temperature Switch. This device will activate when the engine coolant leaving the engine
exceeds 220 ± 3.5°F (104 ± 2°C).
Low Oil Pressure Switch. This device activates when the engine lubrication oil pressure falls below 15 ±
3 psi (103.4+ 20.7 kPa).
Low Fuel Level Float Switch. This device will activate when the fuel level falls to a point at which the operat-
ing time of the set at rated load is four minutes.
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.
Overspeed Relay. This device will activate when the engine speed exceeds 2200 ± 40 RPM.
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.