A Novel Spoke-Type PM Machine Employing Asymmetric Modular Consequent-Pole Rotor

Abstract

This paper proposes a novel spoke-type permanent magnet (PM) machine, which adopts asymmetric modular consequent-pole (AMCP) rotor to enhance the effective PM flux due to the increased flux-focusing effect and reduced leakage flux and to improve the flux-weakening capability due to the increased d -axis inductance. Moreover, the pole-shaping method based on three sectional arcs is proposed to suppress the harmonics of airgap flux density. Since the rotor structure is relatively complex, the finite-element analysis together with multiobjective genetic algorithm is adopted to optimize this design. Furthermore, the electromagnetic performance of the spoke-type PM machine with the proposed AMCP rotor (Spoke-AMCP), including the open-circuit airgap flux density, phase back electromotive force, torque, PM utilization ratio, efficiency, and flux-weakening capability, are compared with two conventional spoke-type PM machines with evenly distributed and alternate flux barriers (Spoke1 and Spoke2) and consequent-pole spoke-type PM machine (Spoke-CP). It is demonstrated that the Spoke-AMCP machine obtains the largest output torque and PM utilization ratio, lowest torque ripple and similar efficiency compared to Spoke1, Spoke2 and Spoke-CP machines. Moreover, although the Spoke-AMCP machine has the largest PM flux linkage, it has slightly better flux-weakening capability than the Spoke1 and Spoke2 machines. Finally, a 12-slot/10-pole Spoke-AMCP machine is built and tested to verify the analyses.