TM 5-3805-294-23-1
0003
HYEX THEORY OF OPERATION - Continued
Engine Electronic Control System - Continued
Table 2. Engine Speed Control System Operation - Continued.
Fast Idle - HP Mode (arm in over
Speed
19502050 rpm
relief)
Fast Idle - P Mode
Speed
18501950 rpm
Fast Idle - E Mode (no load)
Speed
17001800 rpm
Travel HP
Speed
19502050 rpm
Auto Idle
Speed
11501250 rpm
Auto Warm-up
Speed
13001500 rpm
Idle Speed-up
Speed
850950 rpm
Fast Idle Speed Heater Control
Speed
19502050 rpm
ELECTRICAL SYSTEM
The HYEX uses a 24-volt electrical system. The HYEX is equipped with:
Batteries
The batteries provide power for engine starting and other electrical circuits. Two 12-volt batteries are connected in
series to provide 24-volt starting power.
The alternator is located in the engine compartment on the upper front of the engine. It provides 28-volt, 80-amp.
current to charge the batteries and operate the electrical system. The alternator uses a rotating magnetic field with
stationary windings. The magnetic field is externally excited. This means that it requires an outside current source.
The rotor (Figure 9, Item 62) consists of two interlocking soft iron sections and a wire coil wrapped around an iron
core. When current is passed through the wire coil, the rotor becomes an electromagnet. The rotating magnetic field
induces an alternating current in the stator windings (Figure 9, Item 63). This is converted to direct current by six
diodes in the rectifier bridge (Figure 9, Item 64). A capacitor inside rear housing protects rectifier bridge and diode
trio (Figure 9, Item 65) from voltage surges. It also suppresses radio interference. This alternator uses an "A" field
circuit with regulator located after field. Full output is obtained by grounding field.
0003-11