Simulations and experiments on eddy current in Nd-Fe-B magnet

Eddy current loss in Nd-Fe-B sintered magnets was investigated from experimental and simulated aspects. Eddy current loss was estimated from the temperature rise rate of a thermally insulated magnet when an ac field is applied to the solenoid coil. Eddy current simulation is done by the integral element method (IEM) and finite element method (FEM). Both simulation results are compared and the accuracy of simulation is verified. IEM is mainly used for loss analysis. Both simulation results also agree well with the experimental ones. In order to reduce the eddy current loss, the effect of dividing a magnet into several segments was revealed. In an actual motor, the ac magnetic field contains higher harmonic elements. So, in order to consider higher harmonics effect on eddy current loss in Nd-Fe-B magnet in an eddy current problem, a simple addition of individual harmonic and mixing wave is investigated and compared.