Multi-Phase Flux-Switching Permanent Magnet Brushless Machine for Aerospace Application

Flux-switching permanent-magnet (FSPM) brushless machines have attracted considerable interest as a candidate machine technology for applications requiring high torque density and robust rotors. To date, published findings have focused exclusively on single and three phase FSPM machines. This paper investigates FSPM brushless machines of higher phase numbers, by means a detailed comparison of the electromagnetic performance of 3-, 4-, 5-, 6-phase variants within the specific context of aerospace generators. Machines having both all poles and alternate poles wound are investigated, the latter offering scope to reduce mutual coupling between phases so as to achieve improved fault-tolerance. The finite element predicted back-EMF waveforms are experimentally validated on small 5-phase FSPM machines having all poles wound and alternate poles wound. The nature of the generator specification requires that consideration must be given to mechanical stress in the rotor and the trade-off with electromagnetic design considerations, notably the degree of rotor saliency which can be incorporated. Therefore, a mechanical finite element study of the rotor mechanical stresses of multi-phase FSPM machines is also comparatively assessed.