field discharge resistor - small hydro generator
field discharge resistor - small hydro generator
(OP)
I have a hydro generator that is 12.5MVA, 13.8KV. The rated field volts and amps are 250V, 240A; and according to my datasheet the field resistance is 0.904 ohms. The rotating exciter has nameplate info of: 80KW, 250V, 320A, shunt wound. I am removing a field breaker that is in the exciter field and installing a field breaker in the generator field. How do I figure the size of the field discharge resistor? My research so far tells me that it should be 1 to 1.5 times the field resistance, is that right? How do I determine the Watt rating?





RE: field discharge resistor - small hydro generator
It is (or was) quite common to use a contactor that connects the discharge resistor and then open the field winding connection. Then, the energy that the resistor must absorb is equal to the energy in the excitation winding (or half of it, actually). If (assuming a time constant around 5 seconds) the energy that the discharge resistor needs to absorb is something like 144 000 Ws.
That is a lot of energy and you will probably need a discharge resistor able to dissipate at least a few kW continuously. I would go to a reputable power resistor manufacturer and get advice from him.
It is also possible to disable the rotating exciter by opening its excitation winding. That will not need a big discharge resistor. But may be unsuitable for reasons that I don't know anything about.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: field discharge resistor - small hydro generator
RE: field discharge resistor - small hydro generator
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: field discharge resistor - small hydro generator