VP22-03 Modeling and Suppression of Torque Ripple of Direct-Drive V-Shape Permanent Magnet Motor Considering Effects of Stator Teeth and PM Shape
Creators: Deyang Fan
Xinyang Chen
and Xiaoyong Zhu
Publisher: name: IEEE
Year: 2025

Recently, vernier permanent magnet motors have become competitive candidates for low-speed, high-torque direct-drive applications. In this kind of motor, by the design of three elements (PMs, flux modulators, and windings), not only fundamental airgap magnetic field harmonics would contribute to the production of motor output torque, so motor torque density can be effectively increased. However, such airgap flux harmonics would also inevitably produce additional torque pulsations, which limits the further applications of permanent magnet vernier motors. Recently, many torque ripple reduction methods have been proposed, including segmented rotor, rotor notching, and slot skewing [1], [2]. However, current publications often try to suppress torque ripple only from the perspective of flux modulators, while the influence of other elements of magnetic field modulation theory is often ignored. In this paper, torque ripple generation mechanism is analyzed analytically and a novel motor torque ripple reduction approach is proposed, in which both shapes of PMs and rotor are considered comprehensively. Fig. 1 (a) and (b) show the motor structure of the original and proposed direct-drive delta-shaped PM (DS-PM) motor respectively, and the corresponding detailed rotor topologies are presented in Fig. 1(c) and (d). As can be seen, additional harmonics are injected in the rotor and PM shape simultaneously. Fig. 2 shows the comparison of the magnetic field modulation process of two DS-PM motors. Furthermore, Fig. 3 illustrates the configuration of the shaped rotor and PM. Fig. 4 and Table I show the electromagnetic performance comparison between the original and proposed DS-PM motor. As can be seen, with the assistance of the shaped rotor and PM, while the motor average torque is almost the same, motor cogging torque and torque ripple have reduced by 81.4% and 73.7% respectively. It is indicated that, by the artful introduction of shaped rotor and PM, reduced torque ripple can be realized effectively, which provides a new research path for the design of low-torque ripple PM motors. More simulation, optimization, and experimental results will be presented in the full paper.References: [1] M. Jiang, X. Zhu, Z. Xiang, S. Zheng, D. Fan, and W. Chen, "Dual-Sub-Region Rotor Design of a Permanent Magnet Hub Motor with Enhanced Speed Regulation and Output Torque for Electric Vehicles," IEEE Transactions on Industrial Electronics, doi: 10.1109/TIE.2024.3370946. [2] L. Fang, D. Li, X. Ren, and R. Qu, "A Novel Permanent Magnet Vernier Machine with Coding-Shaped Tooth," IEEE Transactions on Industrial Electronics, vol. 69, no. 6, pp. 6058-6068, June 2022, doi: 10.1109/TIE.2021.3088331.
Recently, vernier permanent magnet motors have become competitive candidates for low-speed, high-torque direct-drive applications. In this kind of motor, by the design of three elements (PMs, flux modulators, and windings), not only fundamental airgap magnetic field harmonics would contribute to the production of motor output torque, so motor torque density can be effectively increased. However, such airgap flux harmonics would also inevitably produce additional torque pulsations, which limits the further applications of permanent magnet vernier motors. Recently, many torque ripple reduction methods have been proposed, including segmented rotor, rotor notching, and slot skewing [1], [2]. However, current publications often try to suppress torque ripple only from the perspective of flux modulators, while the influence of other elements of magnetic field modulation theory is often ignored. In this paper, torque ripple generation mechanism is analyzed analytically and a novel motor torque ripple reduction approach is proposed, in which both shapes of PMs and rotor are considered comprehensively. Fig. 1 (a) and (b) show the motor structure of the original and proposed direct-drive delta-shaped PM (DS-PM) motor respectively, and the corresponding detailed rotor topologies are presented in Fig. 1(c) and (d). As can be seen, additional harmonics are injected in the rotor and PM shape simultaneously. Fig. 2 shows the comparison of the magnetic field modulation process of two DS-PM motors. Furthermore, Fig. 3 illustrates the configuration of the shaped rotor and PM. Fig. 4 and Table I show the electromagnetic performance comparison between the original and proposed DS-PM motor. As can be seen, with the assistance of the shaped rotor and PM, while the motor average torque is almost the same, motor cogging torque and torque ripple have reduced by 81.4% and 73.7% respectively. It is indicated that, by the artful introduction of shaped rotor and PM, reduced torque ripple can be realized effectively, which provides a new research path for the design of low-torque ripple PM motors. More simulation, optimization, and experimental results will be presented in the full paper.References: [1] M. Jiang, X. Zhu, Z. Xiang, S. Zheng, D. Fan, and W. Chen, "Dual-Sub-Region Rotor Design of a Permanent Magnet Hub Motor with Enhanced Speed Regulation and Output Torque for Electric Vehicles," IEEE Transactions on Industrial Electronics, doi: 10.1109/TIE.2024.3370946. [2] L. Fang, D. Li, X. Ren, and R. Qu, "A Novel Permanent Magnet Vernier Machine with Coding-Shaped Tooth," IEEE Transactions on Industrial Electronics, vol. 69, no. 6, pp. 6058-6068, June 2022, doi: 10.1109/TIE.2021.3088331.