Design and Analysis of a Flux Reversal Machine With Evenly Distributed Permanent Magnets

In this paper, a flux reversal machine (FRM), which has a larger torque density and a smoother torque waveform than the conventional FRM, is introduced. The FRM has the same combinations of stator and rotor slots, winding pole pair, and permanent magnet (PM) usage as the conventional FRM, but has different PM arrangements, i.e., in the conventional FRM, a pair of PMs is mounted on the surface of each stator teeth while the PMs of the FRM introduced in this paper are evenly distributed along the inner surface of the stator. First, the origination from the conventional FRM to the proposed FRM is introduced. Then, the effects of the rotor slot number, split ratio, stator/rotor slot opening ratio, PM thickness, and pole arc on the average torque and cogging torque are investigated and analyzed, which give a reasonable prediction for maximum achievable power density and minimum possible cogging torque of the proposed FRM. Moreover, the proposed FRM is compared with a conventional FRM in terms of back electromotive force, rated torque, pulsating torque, power factor, and overload capabilities. Finally, a 12-stator-slot/17-rotor-slot FRM prototype is built to verify the theoretical analyses.