No Voltage

1. voltmeter faulty or faulty connection of voltmeter

Check voltage at alternator terminals with multimeter. Replace the voltmeter or correct or repair the connection to voltmeter.

2 Loss of residual voltage

Check residual voltage at alternator it should be more than 5 v .Flash the exc. stator with 12 v / 24v external dc supply (battery) after isolating exc. field connection from the AVR.

3. Excitor stator connection to AVR must be reversed.

Reverse the connection of excitor stator to AVR.

4. Low Insulation resistance to earth on excitor stator or main stator

Check the IR value with megger after disconnection of AVR. If the harness or terminal wire of the excitor stator or main stator faulty replace or repair the same. If not heat the winding with heaters for some period.If not call the machine to works.

5. RRA diodes faulty.

Replace the diodes after checking the diodes with multimeter.

6 Surge suppressor (Variastor assembly) short circuited.

Check the same with multimeter. Replace the same if found faulty.

7. AVR Harness and connection must be faulty or AVR must be faulty.

Check the voltage at AVR input and output. If found faulty check the harness and AVR connection. Correct the same if found faulty. If the above is OK and no output from AVR. Replace the AVR.

8. Winding fault. Open circuit or short circuit on any of the windings.Check the winding resistance of the windings. If found not matching with design value as per manufacturer. Call the machine at works.