Generator Field Suppresion Contactors 1

[Sandles]

I am retrofitting a new excitation system to a 1MVA generator. The existing one has a field suppression contactor on it. I don't see the need. Does anyone have an opinion in this

 

[jbartos]

Suggestions:
1. Check with the generator manufacturer for its need to keep it
2. It depends what kind of retrofit/upgrade will be installed. It just may cover the function of the field suppression contactor, perhaps electronically
3. It beneficially functions during internal faults of the generator. See Reference:
Say M. G., "Alternating Current Machines," John Wiley & Sons, New York, 1978, page 430 "Field Suppression"

 

[peterb]

Is there a field breaker or contactor provided with the upgrade? If yes, then normal design practice would use a "b" contact of the field switch to switch in a field discharge resistor. Of course, the purpose of this is to de-excite the field in the minimum time to remove the fault current source from the system.

 

[Sandles]

Is there any substantial difference to removing the supply to the AVR which feeds a pilot excitor which feeds the main field to shorting out the main field using a contact of the CB. Note there is no manual excitation only the AVR

 

[jbartos]

Suggestion: The short-circuited main field will have some current circulating in it; therefore, it will behave as a rotating magnet generating some stator voltage and power.