Influence of Rotor-Pole Number on Electromagnetic Performance in 12-Phase Redundant Switched Flux Permanent Magnet Machines for Wind Power Generation

In this paper, electromagnetic performances of 12-phase 24-stator-pole redundant switched flux permanent magnet (SFPM) machines with 20-, 22-, 26-, and 28-rotor-pole rotors designed for wind power generation are comparatively analyzed. The influence of key design parameters on the open-circuit phase electromotive force and cogging torque is comparatively evaluated by a 2-D finite-element analysis (FEA). FEA results show that the 24-/26-pole SFPM machine exhibits the highest electromagnetic torque and efficiency than the other three, while the 24-/22-pole one has the smallest cogging torque and torque ripple as well as relatively good voltage regulation and efficiency, which are essential for a wind generator. Furthermore, the investigation on redundancy performance shows that cross coupling among the four sets of three-phase balanced windings and the saturation effect can be neglected when the generator operates with relative light loads. Finally, the 12-phase 24-/22-pole SFPM machine is built and tested to validate the simulations.