Analysis of a Triple-Stator Axial-Flux Spoke-Type Permanent Magnet Vernier Machine

In this article, an axial-flux permanent-magnet (PM) Vernier machine with the triple-stator, spoke-type PM rotor, and toroidal winding wound on the innerstator is proposed. Benefited from the flux focusing spoke-type PM rotor and short end length toroidal winding, the proposed machine has a high torque density and the improved power factor. Based on the air-gap permeance function, the analytical expression of the proposed machine is derived to qualitatively analyze the machine's performance. The quasi-three-dimensional (3-D) finite element analysis (FEA) is adopted to optimize the design parameters, such as innerstator diameter, PM thickness, and slot opening width. The quasi-3-D FEA results match well with the 3-D FEA. The 3-D FEA results show the torque densities of the proposed machine reach 49.4 Nm/L and 11.4 Nm/kg, respectively, under the 232 A/cm average electrical loading. The performances, such as overload capacity, PM demagnetization, and PM and core losses, are also analyzed by 3-D FEA. The comparison with the other axial-flux PM Vernier machine is conducted, and the results reveal that the proposed machine has the great advantages of the torque density and power factor. Since the prototype is not built, in this article, the assembly scheme and thermal behavior of the proposed machine are discussed.