Heat Generation in a High Speed PM Electric Motor
Heat Generation in a High Speed PM Electric Motor
(OP)
Howdy,
I am the lead engineer working on a system that uses a high speed PM motor to drive a vacuum pump and blower. I've been working on the cooling requirements for this unit and have been struggling on how much internal cooling Air to supply for the rotor, magnets, and bearings. Calculating the bearing cooling is relativly easy but I have yet to find information on how much heat is generated by the magnet and rotor. I'm just looking for a design rule of thumb. Example, it's a 5KW motor and the losses are .75KW. The losses are assumed heat generation, xx% from the stator and xx% from the rotor.
Any advice or insite to this would be great!
Thanks,
Tom
I am the lead engineer working on a system that uses a high speed PM motor to drive a vacuum pump and blower. I've been working on the cooling requirements for this unit and have been struggling on how much internal cooling Air to supply for the rotor, magnets, and bearings. Calculating the bearing cooling is relativly easy but I have yet to find information on how much heat is generated by the magnet and rotor. I'm just looking for a design rule of thumb. Example, it's a 5KW motor and the losses are .75KW. The losses are assumed heat generation, xx% from the stator and xx% from the rotor.
Any advice or insite to this would be great!
Thanks,
Tom





RE: Heat Generation in a High Speed PM Electric Motor
I'm not sure you'll find a design "rule of thumb". You could calcuate all of the stator losses (I^2R, eddy current, hysteresis etc.) and subtract from the total loss of your machine. Rotor only losses in a PM motor can vary. Do you have magnets that are susceptable to eddy current loss? Any way, most of the loss should be in the stator (I think). You can obtain software to help simulate this (FEA) or Motor-Cad (http://www.magsoft-flux.com/).
RE: Heat Generation in a High Speed PM Electric Motor
"how much internal cooling Air to supply for the rotor, magnets, and bearings."
Can you elaborate?
RE: Heat Generation in a High Speed PM Electric Motor
Tom
RE: Heat Generation in a High Speed PM Electric Motor
It is rather important what you mean by high speed, some say that 10 kRPM is high, others say 100 kRPM. I have run designs at around 80 kRPM and used water cooling for the stator. The intense air circulation in the motor makes for the rotor cooling, so you do not need to supply any air. Only increase water flow to remove the rotor heat.
BTW, we used ceramic ball bearings. The centrifugal forces were too much for the steel balls.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Heat Generation in a High Speed PM Electric Motor
RE: Heat Generation in a High Speed PM Electric Motor
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Heat Generation in a High Speed PM Electric Motor
Bearings are no problem as that is one of our signature specialties. Bearing DNs in the 3 million are not out of our experence.
Tom