Rotor - Kohler 7.5EOR Service

2. Use an ohmmeter on the R x 100 scale to check the
resistance between the rectifier diodes as shown in
Figure 7-17. The ohmmeter should show a low
resistance in one direction and, upon reversing the
ohmmeter leads, a high resistance in the other
direction. Replace the rectifier module if any of the
diodes tests differently than described.
B
1
+
(AC)
B
A
B1
A1 C1
C
1. Diode terminal
Figure 7-17 Testing the Rectifier Module

7.11 Rotor

The generator set rotor (magnetized by DC from the
rectifier module) rotating within the stator windings
induces AC in the stator windings. Test the generator
set rotor (main field) as described in the following steps.
Disassemble the generator set before performing this
test. See Section 9.
Generator Set Rotor Test Procedure:
1. With the generator set disassembled, disconnect
the generator set rotor (main field) windings at the
rectifier module terminals F+ and F--.
2. Check the main field resistance by connecting an
ohmmeter across the main field F+ and F-- leads.
See Figure 7-18.
resistance reading. A low reading indicates an
internal short and a high reading indicates an open
winding. Repair or replace the main field if the
48 Section 7 Generator Troubleshooting
A
--
C
(AC)
-- +
(AC)
See Section 1.3 for the
ohmmeter readings indicate the main field is
inoperative. If the resistance test is inconclusive,
perform a megohmmeter test on the main field as
described in the next step.
3. Check the main field for a short to ground condition
by using a megohmmeter. Apply 500 volts DC to
either field lead and the main field frame. Follow
the megohmmeter manufacturer's instructions for
using the megohmmeter.
reading of 1.5 mOhms and higher indicates the
main field is functional. A reading of less than
1.5 mOhms indicates deterioration of the winding
insulation and possible current flow to ground; if so,
replace the main field.
6
5
4
5966711
1. Main field (rotor)
2. Stator windings
3. Rectifier module
Figure 7-18 Ohmmeter Connections on the Rotor
8
7
1. Main field (rotor)
2. Stator windings
3. Frame connection
4. Shaft connection
Figure 7-19 Megohmmeter Connections on the
See Figure 7-19. A
1
F+
AC
AC
AC
F--
3
4. Ohmmeter
5. Armature
6. Exciter field
1
F+
AC
AC
AC
F--
5
6
5. Rectifier module
6. Megohmmeter
7. Armature
8. Exciter field
Main Field
2
TP-593613
2
3
4
TP-5936514
TP-6073 4/06