Optimal Study of a High Specific Torque Vernier-type Axial-flux PM Machine with Two Different Stators and a Single Winding

This paper presents the optimal study of a verniertype axial-flux permanent-magnet (AFPM) machine, which has a high-polarity spoke-type PM rotor, a wound stator with a low number of coils, and a profiled stator. Both stators have profiled teeth to enhance the magnetic interaction between the rotor PM array and stator windings for torque production. Compared to the topology with two wound stators, the studied one has a smaller total axial length and is expected more suitable for applications where the space is limited in axial direction. Both topologies are optimized through 3-dimensional (3D) finite element analysis (FEA) by the combined design of experiments (DOE) based sensitivity analysis and surrogate-assisted multiobjective differential evolution (DE) algorithm. Key factors affecting the two objectives, i.e., total active material cost and total electromagnetic loss, are identified. The optimization results are presented and compared, providing practical guidelines for the optimal design and operation of such machines. The manufacturing aspects and their impacts on the electromagnetic performance are also discussed.