Comparative Study of Flux-Switching and Doubly-Salient PM Machines Particularly on Torque Capability

Flux-switching and doubly-salient brushless motors are both novel PM machines having magnets in the stator instead of rotor with outstandingly different static characteristics, especially on the PM flux-linkage waveform, namely, the unipolar and quasi-trapezoidal one for the doubly-salient PM motor, whereas bipolar and sinusoidal one for the flux-switching PM motor, which inevitably results in the distinction in the toque capabilities of both motors. In this paper, based on the theoretical analysis and finite element calculation, a comprehensive comparison on the torque performance of the two motors are investigated under five classical working conditions, in which the flux-switching PM motor is operated in brushless AC mode, while the doubly-salient PM motor is run in brushless DC mode. It is found that the flux-switching PM motor has superior torque capability to that of the doubly-salient PM counterpart, which is verified by both the finite element analysis and experimental results.