Core losses in permanent magnet motors

It is pointed out that the conventional approach to core loss prediction using the Fourier series of the space wave of air gap flux density is not applicable to surface mounted permanent magnet (PM) motors. An alternative approach based on the concept that eddy current losses are proportional to the square of the time rate of change of the flux density is presented. Expressions are derived for predicting hysteresis and eddy current losses in the stator teeth and yoke. Prediction of core losses is compared with measurement of losses on a four-pole PM motor, confirming the applicability of the proposed approach