Iron Loss Reduction Method for Permanent Magnet Machine with Beveling Magnet

Permanent magnet (PM) machines can save energy compared with induction motors, because of the elimination of rotor copper loss and the reduction of stator iron losses. In PM machines, iron losses form a most portion of the total losses. In order to further reduce the iron losses, the method of beveling magnet edges is proposed. The expressions of the peak and the time rate change of flux density in the teeth and the yoke are deduced respectively, considering a random angle of beveling magnet edges. According to the basic concept of the eddy current loss, the analytic calculations of the average eddy current loss density in the teeth and the yoke are presented respectively. Using the hysteresis loss density, which depends only on the peak value of the flux density, the analytic calculation model of iron losses is presented. The model is derived from machine dimensions & material properties and can be directly used in machine design. The predictions of overall iron losses are then compared with test on the PM machine.