Comprehensive comparison of novel stator surface-mounted permanent magnet machines

A novel stator surface-mounted permanent magnet (SSPM) brushless machine with doubly-salient structure having magnets in the stator instead of rotor is proposed, which can be regarded as an improved flux-reversal machine. By comparing the electromagnetic performance of alternative topologies with different combinations of stator slots and rotor poles, it turns out that three combinations, namely, 6-stator-slot/4-rotor-pole, 12-stator-slot/8-rotor-pole and 12-stator-slot/10-rotor-pole, have attractive features, e.g., quasi-rectangular or sinusoidal back-electromagnetic-motive-force (back-EMF), relatively low cogging torque, large electromagnetic torque and higher power capability. Further, based on 2-D finite element analysis, a comprehensive comparison between the three topologies is investigated and the significant similarities and differences in topologies, operation principles and electromagnetic performances are highlighted. The results show that the 6/4 or 12/8 SSPM machines are suitable for typical brushless DC (BLDC) operation, whereas the 12/10 one is favorable for brushless AC (BLAC) operation.