Design and Performance Analysis of a Novel Axial-Flux IPM Machine for Electric Vehicles

To solve the problems of poor flux-weakening ability and insufficient utilization of reluctance torque for the axial-flux surface-mounted permanent magnet (AFSPM) motor, a new type of axial-flux interior permanent magnet (AFIPM) rotor topology is proposed in this article. First, the electromagnetic topology of the proposed axial-flux motor with an IPM rotor is introduced. The working principle of the proposed IPM rotor is analyzed by the magnetic circuit and preliminarily designed for the electric vehicle traction application. Then, considering the calculation time consumption of multiobjective optimization with 3-D finite element analysis (FEA), a 2-D equivalent model is developed to optimize the geometric parameters of the AFIPM rotor. Furthermore, electromagnetic performances are compared with the state-of-the-art AFSPM and single U-shaped designs to highlight the advantages of the presented novel AFIPM machine in power/torque density and flux-weakening capability. The torque capacity of the new AFIPM motor is improved by utilizing reluctance torque, while the high saliency ratio enhances the constant power speed range. Finally, the proposed AFIPM motor is manufactured and experimented. The experimental results further confirm the correctness of 3-D FEA calculation and equivalent optimization results with a 2-D model. Meanwhile, the advantages of the new AFIPM rotor for high utilization of reluctance torque and high torque/power density are also demonstrated.