
126 SEBU8219-01
Maintenance Section
Varistor - Test
i01494879
Varistor - Test
SMCS Code: 4466-081
g00677004
Illustra
tion 88
PMPE Generator W iring Diagram
(CR1-CR6) Diodes
(CR7) Varistor
(L1) E xciter field (stator)
(L2) Ex citer armature (rotor)
(L3) Main field (rotor)
(L4) M ain armature ( stator)
(L5) P ilot exciter armature
(PM) Permanent magnet
(RFA) Rotating field assembly
(CST) Customer supplied transformer
Ohmmeter
An ohmmeter
canbeusedtocheckavaristor
(CR7). Place an ohmmeter across the varistor. The
resistance should be a minimum of 15000 ohms. If
the resist
ance is less than 15000 ohms, the varistor
is faulty.
Test Light
g00555113
Illustration 89
Tes t Light
Refer to the test light that is shown in Illustration 89.
Follow these steps in order to test the varistor:
1. Disconnect either lead of the varistor (CR7).
2. Place the test light across the varistor.
3. Observe the results. The lamp should not light.
4. Reverse the test light.
5. Observe the results. The lamp should not light.
If the test light illuminates in either direction, there is
a short in the varistor. Replace any faulty varistors
with varistors that have comparable operating
characteristics. Include the following information
when a varistor is being ordered for replacement:
•
Part number of the varistor
•
Serial number of the generator
After the varistor has been replaced, verify that the
strapping of the field winding lead is securely wound
on the shaft. Also, verify that the strapping of the field
winding lead is securely tied.
i0149186
8
Voltage and Frequency - Check
SMCS Code: 4450-535-EL
Check for
the proper voltage setting and check for
the proper frequency setting. Check for stability.
For the co
rrect voltage and frequency, refer to the
generator set’s Serial Plate.