Cogging torque reduction for radially laminated flux-switching permanent magnet machine with 12/14 poles

Flux-switching permanent-magnet machine (FSPMM) offers high torque density, impressive flux weakening capability and mechanical ruggedness because of its distinctive configuration, and is potentially suitable for the application in the plug-in hybrid electric vehicle (PHEV). However, the FSPMM compared with other traditional machines commonly used in the PHEV generally exhibits higher cogging torque for its double salient structures of both stator and rotor poles. Furthermore, the back EMF wave including odd harmonics especially 3rd and 5th ones are not ideally sinusoidal that could bring some extra copper loss and decrease its efficiency. Hence, how to minimize the cogging torque so to reduce the torque ripple, and how to reduce the total harmonic distortion (THD) of the back EMF wave are important issues in the field of FSPMM. Four rotor topologies in this paper are proposed to suppress the cogging torque and make the back EMF more sinusoidal for an FSPMM with 12/14 (stator/rotor) poles so as to make it more suitable to the brushless AC (BLAC) operation. Plenty of theory analysis and quantitative comparisons are made between different schemes. The validity of the proposed techniques has been confirmed by 2-D models of the finite element algorithm (FEA) executed in commercial software, Ansoft Maxwell 12.