9-2
GENERATOR OPERATION
Refer to the schematic in Section
12. Wiring Sche-
matic/Diagram
that corresponds to your genset to
follow the generator operating description. Always
refer to the specific schematic that corresponds to
the model and spec number of the genset when
troubleshooting problems.
When the Start/Stop switch is placed in the START
position, the rotor begins to turn and the field wind-
ing is momentarily connected to the battery. This
provides a current in the field winding to provide
magnetism for voltage buildup. As the engine starts
and speed increases, the rotating field induces an
AC voltage in the stator windings. AC voltage from
the excitation winding (Q1-Q2) is fed to the voltage
regulator where it is rectified into DC voltage and
fed back into the rotor to cause further voltage build-
up. This process continues as the engine picks up
speed. Voltage buildup is controlled by an electron-
ic voltage regulator that is connected to the power
output leads (L1-L2). The regulator continually
measures the output voltage and compares it to an
internal reference voltage. When the output voltage
exceeds the reference, the regulator causes the
current in the rotor to decrease until the proper volt-
age is obtained.
During operation, the regulator is continually moni-
toring the output voltage. When additional load is
applied to the generator, the output voltage starts to
decrease. The regulator senses this decrease and
increases the field current until the reference volt-
age and the output voltage match. Similarly, when
the load is decreased the output voltage begins to
increase and the voltage regulator senses this in-
crease. In this case, the regulator decreases the
amount of current to the field until the output voltage
again matches the reference voltage. By continual-
ly measuring the output voltage and compensating
for load changes, the electronic voltage regulator
keeps the voltage of the generator constant with
varying load conditions.
GENERATOR SERVICE
This section covers generator disassembly and as-
sembly procedures. Refer to Figure 9-1 on Page
9-3 and Figure 9-2 on Page 9-4 to identify the var-
ious generator components described in each sec-
tion. Raising the generator and engine assembly
above the base assembly is necessary to disas-
semble the generator. Lifting eyes are provided on
the starter bracket and endbell assembly on the
Spec A models. A lifting hoist will be required for this
step.
Generator Disassembly / Base Removal
1. Drain the engine oil while the genset is still
mounted in the vehicle.
2. Remove the genset from the vehicle and place
it on a sturdy work bench. Refer to
Set Removal
Guidelines
on Page 5-2 for the recommended
genset removal procedures.
WARNING
The genset is heavy and can re-
sult in severe personal injury if dropped
during removal or service. Use the recom-
mended removal techniques and keep
hands and feet clear while removing
mounting bolts.
3. Remove the side mounting screws from the en-
closure cover and lift cover off genset. (Begin
Spec B, 50 Hz models: Remove the leads from
the battery charger assembly mounted to the
left side of the housing.)
Spec A Instructions:
4. Remove the engine mounting bolt and two gen-
erator mounting bolts (T-55 driver) from under
the base assembly. (Apply antiseize lubricant
to the treads of these bolts before reinstalla-
tion.)
5. Remove the muffler exhaust mounting bolts
from the base assembly.
6. Remove the mounting screws from the voltage
regulator, the control panel and the solenoid/
control module bracket.
7. Lift the solenoid/control module bracket and re-
move the ground terminal block from the left
side of the base assembly. Disconnect the fuel
pump leads. Disconnect the AC ground, neu-
tral (L2) and load (L1) leads if they were not dis-
connected during genset removal.
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