We have a 625KVA Cummins generator for using as Emergency Diesel Generator (EDG) as a back up during black out. But its frequency varies from 49.5 HZ to 50.5 Hz during running. Since for the ups & down of frequency the generated voltage also fluctuates. Can anyone please inform me the real cause of this problem.

 

If this is occurring in both unloaded and loaded running, then the governor and/or fuel rack has a problem. Either the governor is not tuned properly, and/or the fuel rack is binding or the mechanism that's operating the fuel rack is sticking or not functioning properly.

If the voltage is also fluctuating, then it sounds like the exciter regulator (or voltage regulator, or "AVR", Automatic Voltage Regulator, as it's commonly called) is also not tuned very well. If the voltage decreases when the frequency decreases, and increases when the frequency increases, then it seems the exciter regulator is holding excitation constant instead of adjusting it to maintain a specific generator terminal voltage setpoint.

 

Thanks for your information.I have to check those things before i get back.