Component Testing and Adjustment 7-23TP-5606 6/02
Stator
Stator
Rotor
Megohmmeter
Exciter Field
Exciter Field
Exciter
Armature
Frame
Connection
P7 P6
P4 P4
To
Controller
To
Voltage
Regulator
2
FN
112
FP F2 F1
Figure 7-20. Megohmmeter Connections
on Exciter Field
Exciter Armature
The exciter armature, used only on three-phase
generator sets, supplies excitation current to the
generator main field (through the rectifier module). Test
the exciter armature as described in the following steps.
(The generator must be disassembled prior to
performing this test.)
1. With generator disassembled, disconnect
armature leads from rectifier module AC
terminals.
2. With an ohmmeter on the R x 1000 scale, check
resistance across exciter armature leads. See
Figure 7-21. The armature resistance is found in
Specifications--Generator of Section 1. No
continuity indicates an open armature winding. If
the resistance test proves inconclusive, perform a
megohmmeter test on the exciter armature as
described in the next step.
NOTE
Most ohmmeters will not provide accurate
readings when measuring less than one ohm. The
exciter armature can be considered good if a low
resistance reading is obtained (continuity) and
there is no evidence of shorted windings (heat
discoloration).
Exciter
Armature
Exciter
Field
Main Field
710
Stator Windings
Rectifier
Module
AC
AC
+
-
Ohmmeter
Figure 7-21. Exciter Armature
Ohmmeter Test
Hazardous voltage.
Can cause severe injury or death.
Operate the generator set only when
all guards and electrical enclosures
areinplace.
Moving rotor.
WARNING
Hazardous voltage can cause severe injury or
death. Perform electrical service only as prescribed in
equipment manual. Be sure that generator is properly
grounded. Never touch electrical leads or appliances
with wet hands, when standing in water, or on wet
ground as the chance of electrocution is especially
prevalent under such conditions. Wiring should be
inspected at the interval recommended in the service
schedule--replace leads that are frayed or in poor
condition. The function of a generator set is to produce
electricity and wherever electricity is present, there is
the hazard of electrocution.
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