Hobart 6824-1, Operation And Maintenance Manual, Page: 30 / 214

(2)
Engine and generator controls
a. Engine-generator control switch
The engine-generator control switch (5) (also identified as the “build-up-voltage, generate,
idle” switch)
is a three-position toggle type. It is spring-loaded in one position,
BUILD-UPVOLTAGE, and will automatically reposition to GENERATE position when
released. In BUILD-UP-VOLTS position it performs a dual function. First, it supplies power to
the governor control box, which allows the engine to operate at normal governed speed;
second, it momentarily supplies current for closing the excitation-deenergization relay
(3, Fig.
7) contacts, to make three-phase, 115-V AC power available to the voltage regulator, or to
the manual voltage control circuit for excitation of the generator exciter. In GENERATE
position, power is maintained to the governor control box and to the excitation relay
(3, Fig.
7) . When the switch is placed in IDLE position, power is disconnected so that the engine
returns to idle speed and the exciter field is deenergized.
b. Contactor control switch
This is another three-position, toggle switch (7, Fig. 9) identical to the engine-generator
control switch. When placed in the spring loaded CLOSE 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 the plug interlock and fuse interlock
relays. 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 allows the contactor to open.
c. Instrument light and switch
A shielded, instrument panel light
(1)
is mounted at the left side of the control panel. It is
controlled by a toggle switch (3) , which also controls instrument lights on the control box.
d. Engine starting circuit
The pushbutton start switch (15) and permissive toggle switch (18) serve to connect power
for closing an auxiliary solenoid switch. The auxiliary switch then connects power to the
starter solenoid which functions to engage the starter gear with the flywheel ring gear and
apply power to the starter motor to crank the engine. The auxiliary solenoid switch is
necessary because the start pushbutton switch is not capable of carrying the high amperage
flow to the starter solenoid which would result if the starter gear and ring gear should fail to
engage. The permissive toggle switch
(18) also stops the engine when the toggle is placed
in the down
(STOP)
position.
e. Indicating lights
A green indicating light (14) glows to indicate that power is available to the engine protective
system. The light operates only when the engine is running and fuel pressure is sufficiently
high to close a fuel pressure switch. The purpose of the pressure switch is to deactivate the
protective circuit when the engine is stopped and prevent battery discharge.Another green
indicating light
(9, Fig. 9) glows when the generator output load contactor is CLOSED and
power is available at the generator output terminal panel (13, Fig. 3).
f. Cold weather starting aid control
The push-pull control (11) controls operation of a cold weather starting aid (Fig. 3). The
starting aid consists of a group of items designed to inject a highly volatile fluid into the
engine air intake system to assist ignition of fuel when air temperature is too low for the heat
of compression to ignite a normal fuel mixture. The starting aid consists of a cylindrical, fluid
container and a valve
(see 1-3, Fig. 4) which are mounted on the lifting yoke. The valve is
operated by the control (11, Fig. 9) . Pulling the control outward allows fluid to flow into the
valve. Pushing the control IN forces fluid through a small tube and an atomizing nozzle into
the inlet manifold. The addition of atomized, highly volatile fuel into the inlet air assists in
igniting the diesel fuel mixture.
OM-499
1-1 May 31/94 Revised
Page 16