generator rotor shaft current
generator rotor shaft current
(OP)
hello,
What is the permissible value of generator shaft current? I read somewhere else that the permissible value of shaft current shall be less than 1 ampere.
I am expecting your valuable comments.
Regards,
appunni
What is the permissible value of generator shaft current? I read somewhere else that the permissible value of shaft current shall be less than 1 ampere.
I am expecting your valuable comments.
Regards,
appunni






RE: generator rotor shaft current
Hydro-electric usually has shaft current monitor that can be set in the 100 - 1000 mA range. So that seems to be acceptable values in such macines. Don't know about the others.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: generator rotor shaft current
Shaft voltages of up to 50 volts are quite common in hydrogenerators. The oil film between shaft and bearing cannot be regarded as a safe barrier between these components. It therefore is imperative to insulate one of the generator bearings. A generator should be taken off line as soon as the shaft current monitor indicates an insulation breakdown. The low resistance of the shaft current circuit can be responsible for currents of 100 amps and more, far beyond the figures a shaft current monitor can be set.
I've never heard of a permissible limit figure for shaft currents.
Wolf
www.hydropower-consult.com
RE: generator rotor shaft current
I hope more explanations will be there about this matter.
regards,
appunni
RE: generator rotor shaft current
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If we learn from our mistakes I'm getting a great education!
RE: generator rotor shaft current
ScottyUK is right with his comment. Even the arcing of a few hundred milliamps does degrade the bearing oil and is affecting the bearing and shaft surfaces, it only takes more time until the bearing in question fails. This can result in an outage of weeks if not months in case the shaft is damaged. The outage of a 100 megawatt generator, for instance, can lead to a daily loss of revenue of up to 100,000 US$ and more. The correction of a faulty bearing insulation can possibly be done in one day.
Wolf
www.hydropower-consult.com
RE: generator rotor shaft current
regards,
appunni