Influence of adjacent teeth magnet polarities on performance of flux reversal permanent magnet machine

This paper provides a comprehensive analysis of performance difference among various kinds of flux reversal permanent magnet (FRPM) machines having different PM arrangements. Four PM arrangement types are firstly identified by the number and relative polarities of PMs on the stator teeth, and their influence on equivalent pole-pair number of armature winding and working harmonics of air-gap field is revealed. Then, the torque variation against rotor pole number of each PM arrangement is analyzed. Detailed electromagnetic performance of four PM arrangements with 14-pole rotor is compared. It shows that the FRPM machine, in which four PM pieces are mounted on each stator tooth and two adjacent magnets on different stator teeth are of opposite polarities, offers the highest torque density and the highest efficiency, which makes it promising in low-speed high-torque applications. In addition, four prototype machines are manufactured and tested to validate the findings.