TROUBLESHOOTING THE M998 ELECT SYST. - OD1617 - LESSON 1/TASK 1
the batteries, the starter, and the power control box (PCB).
(2) Alternator.
Most military vehicles are now equipped with an
alternating current (AC) charging system. The reason for changing to
an AC system is that an alternator is capable of producing a higher
voltage at idle speed.
Many of the military vehicles are equipped
with radios, a firing device, and other high-current-drawing
equipment.
When this equipment is in operation, and the vehicle's
engine is operating at a low rpm, a direct current (DC) generator
would not produce the required current and voltage to keep the
batteries charged plus supply the current required to operate the
accessories properly.
Alternators convert mechanical energy to
sufficient electrical energy to power the vehicle's electrically
driven equipment.
(a) Basic Alternator Construction.
The alternator is composed
of the same basic parts as a direct current (DC) generator. There is
a field called a rotor, and a generating part known as the stator.
The purpose of the alternator is to produce more power than a
generator and operate over a wider speed range. The construction of
the functional parts is, therefore, different than those of a DC
generator.
The stator is the section in which the current is
induced. It is a slotted, laminated ring with the conductors placed
in the slots. The current generated in these windings is transferred
to the system through three stationary terminals.
(b) Three different amperage rated alternators can be found on
the HMMWV.
One is the 60 amp alternator which is similar to the
alternator used on the M151. It is mounted on the left side of the
engine and is driven by dual drive belts from the crankshaft pulley.
A slotted bracket allows for belt tension adjustments. The other two
alternators are the 100 amp alternator which is found predominantly
on the shelter carriers (M998 and M1037), and the 200 amp alternator
which is used mainly on the ambulance (M996 and M997).
(3) Starter.
Any internal combustion engine must be cranked to
start it running on its own. Early automotive vehicles were started
manually through the use of a handcrank. A system for cranking the
engine with an electric motor was
3
Previous Page
