Retaining sleeve for rotor magnets
Retaining sleeve for rotor magnets
(OP)
What could be the effects of adding a thin 303 to 316 stainless steel sleeve to retain the rotor magnets in a BLDC motor? What would be the best material to use for this sleeve to avoid affecting motor Kt?





RE: Retaining sleeve for rotor magnets
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(2B)+(2B)' ?
RE: Retaining sleeve for rotor magnets
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(2B)+(2B)' ?
RE: Retaining sleeve for rotor magnets
RE: Retaining sleeve for rotor magnets
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Retaining sleeve for rotor magnets
If we use a 316 stainless steel that is annealed will the magetic properties of the steel be reduced enough to not impact the motor Kt?
RE: Retaining sleeve for rotor magnets
http://www.azom.com/details.asp?ArticleID=1140
http://en.wikipedia.org/wiki/Stainless_steel
http://www.ssina.com/faq/index.html
One small Caveat the 1st link indicates some austenetic steels may become magnetic thru cold-working, but apparently applies to 304 and not 316
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(2B)+(2B)' ?
RE: Retaining sleeve for rotor magnets
RE: Retaining sleeve for rotor magnets
It is a common problem when you use variable frequency to feed PM motors. You may need to filter the inverter output voltage or use a sine inverter.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Retaining sleeve for rotor magnets
I guess the best compromise is to use stainless steel, as their conductivity is usually rather low, and they are usually non-magnetic.
I have seen also some manufacturers using some kind of hard plastic tube around rotor (with some small servomotors). From magnetic properties point of view, that is a good choice, but if there are some losses in the rotor, it will also insulate the rotor thermally. In worst case, magnets would heat-up and eventually demagnetize. Sleeves that have some conductivity, also act as a "magnetic mirror" for air gap harmonics, prventing them from penetrating the rotor. Non-conducting sleeve lets all the air gap harmonics to pass the rotor and cause extra losses there.