TP-6137 5/03 53Section 9 Generator Troubleshooting
9.4 Rotor Test
The two-pole rotor creates the magnetic field needed to
raise the alternating current in the stator windings.
Before testing, inspect the rotor for visible damage to the
pole shoes, insulation, and exposed coil windings.
Check the rotor bearings for noisy operation, excessive
wear, and heat discoloration. Replace or repair these
components if any of the above conditions exist.
Procedure to test the rotor’s insulation.
1. Disconnect the two rotor field diodes (D4 and D5).
See the wiring diagrams in Section 11.
2. Using a Megger set at 500 volts DC, check the
winding insulation resistance value to ground.
Check every part isolated from the others. See
Figure 9-2 Normally, windings with a resistance
value to ground greater than 1 MOhm are
considered good. If resistance is lower than 1
MOhm, replace the rotor.
Figure 9-2 Rotor Insulation Test
Procedure to test the rotor’s continuity.
1. Using an Ohmmeter test, check if the rotor winding
is opened. See Figure 9-3. If an accurate
ohmmeter is not available, check the circuit’s
continuity using a 12 VDC battery and a suitable
lamp. See Figure 9-4. Replace the rotor if it is
grounded, has an opened or short circuit.
Figure 9-3 Rotor Continuity Test with Ohmmeter
Figure 9-4 Rotor Continuity Test with AC Test Lamp
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