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Operation and Maintenance Manual
G3516B and G3520B Generator Sets
Media Number -SEBU7566-04 Publication Date -01/11/2004 Date Updated -08/11/2004
i01494879
Varistor - Test
SMCS - 4466-081
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Illustration 1 g00677004
PMPE Generator Wiring Diagram
(CR1-CR6) Diodes
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(CR7) Varistor
(L1) Exciter field (stator)
(L2) Exciter armature (rotor)
(L3) Main field (rotor)
(L4) Main armature (stator)
(L5) Pilot exciter armature
(PM) Permanent magnet
(RFA) Rotating field assembly
(CST) Customer supplied transformer
Ohmmeter
An ohmmeter can be used to check a varistor (CR7). Place an ohmmeter across the varistor. The
resistance should be a minimum of 15000 ohms. If the resistance is less than 15000 ohms, the
varistor is faulty.
Test Light
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Illustration 2 g00555113
Test Light
Refer to the test light that is shown in Illustration 2. Follow these steps in order to test the varistor:
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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.
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