Influence of rotor-pole number on electromagnetic performance in twelve-phase redundant SFPM machines for wind power generation

In this paper, electromagnetic performances of twelve-phase 24-stator-slot redundant switched flux permanent magnet (SFPM) machines with 20-, 22-, 26- and 28-rotor-pole rotors are analyzed. The influences of key design parameters on the open-circuit electro-motive-force (EMF) and cogging torque are comparatively evaluated by 2D finite-element analysis (FEA). FEA results show that the 24/26 SFPM machine exhibits the highest electromagnetic torque and efficiency than the other three, whilst the 24/22 one has the smallest cogging torque and torque ripple as well as relatively good power factor, voltage regulation and efficiency which are essential for a wind generator. Furthermore, the investigation on redundancy 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 light loads. Lastly, the prototyped twelve-phase 24/22 SFPM machine is measured to validate the simulations.