A Novel Spoke-type Asymmetric Rotor Interior PM Machine

This paper proposes a novel spoke-type asymmetric interior permanent magnet (Spoke-AIPM) machine featured by spoke-type symmetrical permanent magnets (PM) and asymmetric flux barrier structure. Without introducing any extra cost comparing with symmetrical designs using the same PMs, this asymmetric rotor topology shows torque enhancement due to magnetic-field-shifting (MFS) effect in the asymmetric rotor structure, which reduces the difference between the current angles for maximum PM and reluctance torque components. Three machines, i.e. the proposed Spoke-AIPM, a spoke-type IPM (Spoke-IPM) with symmetrical flux barrier, and a conventional Spoke-IPM, are designed with the same stator, rotor diameters and PMs. Effects of rotor flux barrier dimensions on maximum torque, constant power speed range (CPSR) performance, and open-circuit flux density for topologies are investigated and the optimal designs are obtained. The electromagnetic performances of three machines are compared, which confirms the torque enhancement of the proposed Spoke-AIPM topology and reveals the enhancement is achieved by MFS effect.