Hobart 9OC24S Operation Manual page 203

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OPERATION, MAINTENANCE, AND OVERHAUL MANUAL, TM-240A
SELF-PROPELLED GENERATOR SET, SPEC. NO. 5381A
SECTION 1. THEORY OF OPERATION
1. General
A thorough understanding of how and why a system operates can be as helpful in
diagnosing trouble as the trouble shooting chart itself.
Knowledge of the various
systems and circuits adds meaning and more clarity to tests and checks used in
locating troubles. Schematic diagrams are used to illustrate circuits. Symbols,
which are identified by a legend on each schematic diagram, are used throughout
the theory of operation to locate and identify electrical components.
NOTE: A. When an item such as a relay contains a coil and a set of contacts,
both are identified by the same legend symbol. For example, on
Figure 2, the coil for the fuse interlock relay is identified by "FIR".
The contacts for this relay are also identified by "FIR 'I.
B. Some components of the engine shut-down system are identified in
Fig. 1 by name rather than by symbol. Example: "FUEL VALVE
SOLENOID".
2. Twelve-Volt Electrical System (See Fig. 1)
In addition to supplying the electrical requirements of engine accessories and shut-down
devices, the 12-V DC system supplies power for the main generator output protective
system. Warning and illuminating lights are also served by this system. Engine safety
devices are shown in Figure 1.
Generator safety devices are shown in Figure 2.
Twelve-volt DC power is supplied by four,
six-volt batteries (Ref. 2-2, Fig. 16).
Batteries are paired and connected in series to produce 12-V DC. Pairs are then
connected in paral le I to produce maximum starting amperage.
A. Engine Shut-Down System
The engine shut-down system consists of electrical and mechanical devices (Fig.
1) designed to stop the engine and prevent damage which could be caused as a
result of low oil pressure or high coolant temperature. The shut-down system
will stop the engine under any one of the following conditions:
Oil pressure - 8 to 12 PSI
Coolant temperature - approximately 205 deg F.
Ott 30/73 3-l
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