VP12-13: A Pole-changing Double-side Flux Modulation Permanent Magnet Motor

Permanent magnet (PM) flux modulation motors are well-known for high torque density compared with conventional PM motors. In this paper, a novel pole-changing double-side flux modulation permanent magnet motor (PC-DSFMM) is proposed based on a PC-PMVM adopting unevenly split modulation tooth structure [1]. The proposed PC-DSFMM is proven to own a considerably higher torque density than the PC-PMVM before and after PC operation due to the double-side flux modulation effect. The motor configuration of the PC-DSFMM is shown in Fig. 1. A PC-winding is installed in 12 stator slots, on which 18 modulation teeth are equipped, and the numbers of modulation teeth on adjacent stator teeth are 1 and 2, forming an unevenly split modulation tooth structure. 6 pieces of PMs are installed on the stator with the same magnetizing direction. Meanwhile, 17 PMs with the same direction of magnetization as rotor PM are half-embedded in the rotor. The original PC-PMVM and its prototype are also shown in Fig. 1 with surface-mounted PM of 17 pole-pairs equipped on the rotor. The two motors are both optimized and have the same assumption of PM. According to the air-gap field modulation theory [2], a fundamental air-gap PM harmonic component with 17 pole-pairs is generated by the PMs on the rotor in the PC-PMVM, which is modulated by the 18 modulation teeth to generate an air-gap PM harmonic of one pole-pair, working as the main source of torque. In the PC-DSFMM, a static air-gap PM harmonic with 18 pole-pairs can be generated by the 6 stator PMs, which interacts with the 17 rotor teeth to increase the amplitudes of the one pole-pair of flux density harmonic. Hence, the torque before and after the PC operation can be increased. The motor performances of the two motors are shown in Table I, where the Mode I and II refer to the motor operation modes before and after PC, respectively. The average torques of PC-DSFMM in Mode I and II are 16.8 and 7.0 Nm, respectively, which are 15.9% and 24.9% higher than those of the PC-PMVM benefitting from the double-side flux modulation effect. Meanwhile, the maximum efficiency, proportion and maximum speed of the high efficiency region (>80%) of PC-DSFMM are slightly smaller than the PC-PMVM.References: [1] Y. Du, Z. He, X. Zhu, etc., A novel pole-changing permanent magnet vernier motor, IEEE Trans. Ind. Electron., vol. 70, no. 6, pp. 6110-6120, (2023). [2] M. Cheng, P. Han, and W. Hua, General airgap field modulation theory for electrical machines, IEEE Trans. Ind. Electron., vol. 64, no. 8, pp. 6063-6073, (2017).