Hobart 9OC24S Operation Manual page 51

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ZMOTOR GENERATOR DIVISION
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HOBART BROTHERS COMPANY
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OPERATION, MAINTENANCE, AND OVERHAUL MANUAL, TM-240A
SELF-PROPELLED GENERATOR SET, SPEC. NO, 5381A
function. First, it supplies DC power to the fuel valve solenoid to hold the
valve open and allow the engine to run.
electric governor control box (27) to all
Second, it supplies DC power to the
ow the governor to function and bring
the engine up to governed speed. Third, it
supplies
DC power to the coil of
the excitation-deenergization relay (24) h h w ic causes it to close and connect
three-phase, 115-V power to the voltage regulator (Fig. 9), which in turn
is then able to supply direct current to the generator exciter field and allow
the generator to produce power. A capacitor (25) is mounted on the excitation -
deenergization relay to prevent any momentary interruption of power to the
relay from stopping operations. When the switch (20) is in GEN position, all
DC power for the above three functions must pass through a "gear-shift" Micro
switch. Any attempt to move the gear-shift lever from NEUTRAL position and
place the transmission in gear wil I automatically open the gear-shift switch
and stop all operations. This is a safety feature to prevent mobile operation
while delivering power. In DRIVE position, DC power is supplied only to the
fuel valve solenoid for engine operation and the gear-shiftsafety switch is
by-passed. For mobile operation, generator excitation is not required, and
engine speed is controlled by an accelerator and flexible cable arrangement
connected to the governor actuator linkage. For mobile operation (DRIVE),
power to the fuel valve must pass through a micro switch in the output cable
plug box (see l-2, Fig. 3), or a series of switches when the unit is equipped
with T-Rs (see l-2, Fig. 5). Output cable, plug connectors hold the Micro
switches closed when connectors are properly stored in the boxes. This feature
insures that all output cables must be disconnected from the aircraft and plug
connectors properly stowed before the vehicle can be driven.
(4) Contactor control switch
This is another three-position toggle switch (17, Fig. 5), similar to the engine
control switch (2) described above. When placed in the spring-loaded ON
position, it
provides
115-V AC power directly to a rectifier which supplies
DC power for closing the load contactor. When released it returns to the
normal ON position and continues to provide power to the rectifier, but in
this switch
position,
AC power must pass through a plug interlock relay and
a fuse interlock to insure that the load contactor will be opened in case the
output cable plug connector is accidentally (or intentionally) disconnected
from the aircraft or if the protective monitor circuit is disabled by the failure
of a fuse. In all cases, power for operation of the load contactor must pass
through the protective monitor. In OFF position the switch opens the AC
circuit to the rectifier, thereby cutting off the source of DC power to the
contactor coil which al lows the contactor to open. An indicating light (12)
glows green when the load contactor is closed.
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