Influence of Rotor Pole Number on Electromagnetic Performance of Double-Stator Switched Flux PM Machines

This paper investigates the influence of rotor pole number on the electromagnetic performance of double-stator switched flux permanent magnet (DS-SFPM) machines. Both stators of the developed machines consist of doubly-salient 6-stator poles, whilst the machines with 10-, 11-, 13- and 14-rotor poles are selected for optimization and comparison. Moreover, the influence of leading design parameters such as the split ratio, PM thickness, rotor-iron arc/pitch ratio and back-iron thickness on the average torque is also investigated. The analyses include the open-circuit coil and phase flux linkages, and the back-EMF waveforms and spectra, the load characteristics, the flux weakening capability and inductance characteristics. The predicted results show that the developed machine with 13-rotor pole number exhibits the largest fundamental back-EMF and thus the largest torque density amongst its counterparts. A prototype is tested for validation.