A Novel Spoke-Type Asymmetric Rotor Interior Permanent Magnet Machine

This article proposes a novel spoke-type asymmetric interior permanent magnet (AIPM) rotor topology that employs an additional asymmetric flux barrier in each pole of interior permanent magnet (IPM) synchronous machines for torque density enhancement and torque pulsating suppression without introducing any extra cost. The proposed AIPM-I machine, an existing spoke-type AIPM-II machine with asymmetric rotor profile, and a conventional spoke-type IPM machine are designed and optimized with the same 12-slot/8-pole stator with nonoverlapping windings as well as the same rotor diameter and PM dimensions. The effect of asymmetric flux barrier dimensions on the proposed AIPM-I machine is investigated with particular emphasis on torque characteristics. The electromagnetic performance and rotor mechanical strength of final optimal designs of three machines are compared. It confirms that the proposed AIPM-I machine can achieve significant torque enhancement and torque ripple reduction across the wide current range while also showing significantly smaller cogging torque at open-circuit condition, compared with both existing AIPM-II and conventional IPM machines. Finally, a prototype of the proposed AIPM-I machine has been manufactured and measured for validation.