PM motor demagnetization
PM motor demagnetization
(OP)
We plan to use a PWM inverter driven PM motor for high transient torque application (a dynamometer for internal combustion engine torque pulse simulation). One of concerns is a theoretically possible loss/reduction of magnetizing capability of rotor mounted magnets due to high transient overheating caused by transient torque. The PM motor supplier can only evaluate thermal processes based on steady state torque application. Is anybody familiar with this kind of problem or might be able to refer to the source of information?





RE: PM motor demagnetization
The ability of rare earth magnets to resist demagnetization decreases with temperature. Samarium Cobalt magnets are much better in this reguard than the Neodyminum magnets. They are also much more expensive. It also depends on the grade of the material. The MCE website shows curves for all their materials. What one is looking for is a straight line demag curve at temperature.
http://www.mceproducts.com/
The thicker the magnets are relative to the air gap length, the better the magnets resist demagnetization.
I'm told at the limit, the magnets start losing strength at their edges.
Having said that, thick Samarium Cobalt magnets are quite difficult to demagnetize.
I believe, for a price, MCE will do magnetic FEA if motor manufactures can provide detailed design information. A static analysis works if the magnet temperature is set and demag is checked at all rotor-stator angles.
Another possibility is to have a custom motor designed and built to your specifications. I can recommend Carlsbad Magnetics.
http://www.carlsbadmagnetics.com/
You might also get additional information by calling both MCE and Carlsbad.
RE: PM motor demagnetization
RE: PM motor demagnetization