Exciter Armature - Kohler 10CCOZ61 Service Manual

Exciter Armature

The exciter armature 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
armature leads
terminals.
2. With an ohmmeter on the R x 1000 scale, check
resistance across exciter armature leads. See
Figure 7-14. 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.
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
Field
AC
Exciter
-
Armature
AC
Rectifier
Module
Ohmmeter
Figure 7-14. Exciter Armature
Ohmmeter Test
TP-5648 8/93
disassembled, disconnect
from rectifier module AC
NOTE
7 10
+
Main Field
Stator Windings
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.
Hazardous voltage can cause severe injury or
death. Follow instructions
manufacturer when performing high voltage test on
rotor or stator. Improper test procedure can damage
equipment or lead to future generator failures.
3. Check exciter armature for a grounded condition.
Using a megohmmeter, apply 500 Volts DC to
either armature lead and armature frame. (Follow
the instructions
manufacturer when performing this test.) See
Figure 7-15. A reading of approximately 500K
ohms (1/2 megohm) and higher indicates the
exciter armature is good. A reading of less than
500K ohms
deterioration of winding insulation and possible
current flow to ground. Repair or replacement of
the exciter armature is necessary.
Exciter
Field
AC
Exciter
-
Armature
AC
Rectifier
Module
Frame
Connection
Megohmmeter
Figure 7-15. Megohmmeter Connections
on Exciter Armature
Component Testing and Adjustment 7-17
of test equipment
of the megohmmeter
(approximately) indicates
7 10
+
Main Field
Stator Windings