ROTOR END RINGS
ROTOR END RINGS
(OP)
Anyone recall if the rotor end rings has one that is constantly positive and the other is constantly negative?
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RE: ROTOR END RINGS
RE: ROTOR END RINGS
RE: ROTOR END RINGS
RE: ROTOR END RINGS
RE: ROTOR END RINGS
RE: ROTOR END RINGS
http://en.wikipedia.org/wiki/Verdigris
I guess some forms of galvanic corrosion would be accelerated by a dc potential (which doesn't exist in induction motor as you say).
I don't think dc potential is required for oxidation of copper. But I certainly don't ever remember seeing any green on any of our large fabricated copper bar rotors (has anyone else?). I would guess that keeping the rotor relatively warm / dry prevents copper from oxidizing ?
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RE: ROTOR END RINGS
"Electrolytic action can occur at slip ring surfaces
producing formation of verdigris. Verdigris is a greenish coating that forms on non-ferrous metals.
Electrolytic deterioration can be prevented by reversing the polarity of the slip rings once or twice a year."
I would imagine that you are right about conditions being dry and warm in preventing this. I assume that perhaps this is seen more with motors that are installed inside pump houses for water supplies or large irrigation applications(where it is cooler and damp)?
RE: ROTOR END RINGS
From the "Kilowatt Classroom" website on synchronous motors (taken from an old Electric Machinery book I used to have, but can no longer find):
"Slip ring polarity is not critical and should
be periodically reversed to equalize the
wear on the slip rings. The negative polarity
ring will sustain more wear than the positive
ring due to electrolysis."