Comparative study of novel biased flux permanent magnet machine with doubly salient permanent magnet machine

A comparative study between the novel biased flux permanent magnet machine (BFPMM) and the doubly salient permanent magnet machine (DSPMM) with the same machine size is presented in this paper. The choice of rotor pole number in BFPMM can be any integers except the phase number and its multiples, which is more flexible than that in DSPMM. Different from 6/4 stator/rotor pole DSPMM which has the unipolar phase flux-linkage and trapezoidal phase back-EMF, they become bipolar and essentially sinusoidal in 6/7 stator/rotor pole BFPMM. Hence, compared with DSPMM under the optimal current angle and rated copper loss, the torque ripple in BFPMM can be reduced significantly by ~70%-80% in both the original design (ORI) and the design with flux focusing technique (FC). Moreover, BFPMM exhibits larger average torque than that of DSPMM in both ORI- and FC-designs under the same copper loss and optimal current angle.