Investigation of AC loss of permanent magnet of SPM motor considering hysteresis and eddy-current losses

NdFeB sintered magnets are widely used in rotating electrical machines. In order to develop an efficient rotating machine, it is important to estimate ac loss of the permanent magnet of rotor precisely. In this paper, the ac losses of the permanent magnet of IEEJ model (surface permanent-magnet motor model) are examined by using the three-dimensional finite-element method taking into account the newly measured hysteresis losses of permanent magnet. The result shows that we should consider not only the eddy-current loss but also the hysteresis loss, when the frequency of ac field due to a slot ripple is of the order of several hundred hertz. Index Terms--Eddy-current loss, hysteresis loss, NdFeB magnet, SPM motor.