Permanent-Magnet Flux-Switching Synchronous Motor Employing a Segmental Rotor

Abstract

This paper introduces a three-phase segmental-rotor flux-switching synchronous motor employing permanent-magnet (PM) excitation in the stator. Flux-switching machines operate with bipolar flux and flux linkages and are therefore associated with high torque densities. Employing a segmental rotor significantly alters the scheme for flux switching from that with toothed rotors but provides a means to deploy radially acting magnets in the stator teeth. The whole arrangement presents advantages of fault tolerance capability, brushless operation, easy cooling, and simplicity of construction. A three-phase motor is developed on a 12-tooth stator with six radial magnets and a rotor with eight segments. Design considerations are applied to the location and shape of the magnets. The developed design has attraction for low-cost applications as the torque capability per unit mass of magnets deployed is found to be about 1.4 times as much as that for conventional PM synchronous motors of the same general size. Measurement results on experimental machines show that the segmented-rotor motor with PM excitation can achieve nearly twice the torque density of the similar-sized segmented-rotor motor with a dc field winding.