The asymmetrical-pole ratio installed in the partitioned stator doubly salient permanent magnet machine (PS-DSPM) is proposed. Its particular outer stator teeth number is varied to improve the electromagnetic performances. The electromagnetic indicators including the magnetic flux distribution, magnetic flux linkage, back-electromotive force (back-EMF), cogging torque, electromagnetic torque, and ripple torque are investigated and then, compared with the conventional PS-DSPM by finite element analysis simulation. The results illustrate that the symmetrical distribution of the magnetic flux firstly is achieved by all proposed machines. The flux linkage magnitude is increased due mainly to the increase of the magnetic flux paths and winding slots when the increased outer stator teeth number. Especially, we found that the asymmetrical-pole PS-DSPM with 30 outer stator teeth has the suitable outer stator teeth number since it can produce the higher back-EMF waveform with a robust outer stator structure than the other proposed machines as well as a conventional machine. Moreover, the average electromagnetic torque with small ripple torque is reached by this proposed machine, which is 39.29% enhanced from the conventional one under the same copper loss. Hence, the asymmetrical-pole PS-DSPM having 30 outer stator teeth is the novel alternative machine for PS-DSPM improvement.

A hybrid-excited doubly salient dual-PM machine (HE-DSDPM) was presented by using the structural multi-tooth modification for an improvement of torque production. The multi-tooth structure modification of HE-DSDPM was clearly described. The PM and stator arcs were further examined for structural optimization. The electromagnetic performance including magnetic flux distribution, flux linkage, back-electromotive force (back-EMF), total harmonic distortion (THD), cogging torque and electromagnetic torque, was investigated with various field current under the same structural constraint. The simulation based on 2-D finite element analysis was used to validate all electromagnetic performance. The results showed that the proposed multi-tooth HE-DSDPM provides the best stator/rotor combination, the appropriate PM characteristics and the enlarged winding slot area. This proposed structure produces better overall electromagnetic performance because of its improved symmetrical magnetic flux path and greater flux regulation quality. In particular, it can generate a larger average torque of 26.18% with the lower ripple torque of about 4% compared to the conventional structure at no field current since the good back-EMF profile and low cogging torque. The largest variance of the torque percentage is occurred when excited by different field currents for the proposed multi-tooth HE-DSDPM. Hence, modification of multi-tooth structure could be beneficial in the electrical machine design of other types of doubly salient structures.