Eddy current losses of permanent magnet motors

A simple and effective method for calculating the core eddy current losses in permanent magnet motors is presented. It uses the back EMF per tooth induced in the stator windings by the rotation of the permanent magnets. The eddy current losses of the stator yoke can also be evaluated as a function of the back EMF per tooth waveform. Simple expressions are obtained for motors with an even number of slots per pole pair. The experimental results refer to a permanent magnet motor with four poles and 36 slots. The proposed method is a general one, which does not depend on the number of motor slots or poles. It gives the possibility of using back EMF waveforms which are acquired experimentally or by numerical methods.