VP22-05 Low-Torque-Ripple Bi-Directional Magnetic Field Modulation PM Motor considering Magnetic Motive Force Distribution Perspective
Creators: Deyang Fan
Hongzuo Tian
Xiaoyong Zhu
Wu Shan
and Zixuan Xiang
Publisher: name: IEEE
Year: 2025

In recent years, bi-directional magnetic field modulation (BD-MFM) motors have attracted considerable attention, due to their inherent advantage of high torque density. However, the bi-directional magnetic field modulation structure often leads to unavoidable high torque ripple and flux leakage[1]-[2]. Therefore, it has been a challenge issue on how to further reduce the torque ripple of BD-MFM motors while maintaining the high torque. In this paper, a novel trapezoidal-shaped PM BD-MFM motor is proposed, the contribution of the proposed motor is presented as follows. Firstly, the relationship among the cogging torque harmonics, airgap flux harmonics, and torque harmonics is investigated. Then, the magneto-motive force of the stator permanent magnets is investigated in detail considering stator PM topology. Finally, to minimize magnetic leakage and cogging torque, the trapezoidal PM structure and rotor magnetic barrier are designed. It provides an effective research path to realize the low-torque-ripple design of BD-MFM motors. Fig. 1(a) illustrates the structures of the proposed trapezoidal PM BD-MFM motor, the reference BD-MFM motor I, and the reference BD-MFM motor II. The reference motor and the proposed motor have the same structure size and permanent magnet dosage. Fig. 1(b) shows the modulation process of the stator-PM MMF and rotor-PM MMF respectively. Fig. 2(a) shows the comparison of the magnetic field distribution and leakage analysis between the proposed trapezoidal PM BD-MFM motor and the reference BD-MFM motor II, and it can be found that the magnetic flux leakage at the airgap is significantly reduced. Fig. 2(b)-(d) shows the comparison results of electromagnetic performances of three motors, including cogging torque, airgap flux density, and output torque. It is noted that the proposed trapezoidal PM BD-MFM motor torque is increased by 4.9 Nm and the torque ripple is reduced by more than 70% which verifies the reasonability and effectiveness of the proposed trapezoidal PM BD-MFM motor. More detailed analysis and experimental verification will be presented in the full paper.References: [1] W. Zhao, Q. Hu, J. Ji, Z. Ling, and Z. Li, "Torque Generation Mechanism of Dual-Permanent-Magnet-Excited Vernier Machine by Air-Gap Field Modulation Theory," IEEE Transactions on Industrial Electronics, vol. 70, no. 10, pp. 9799-9810, Oct. 2023. [2] H. Huang, D. Li, X. Ren, and R. Qu, "Analysis and Reduction Methods of Cogging Torque in Dual PM Vernier Machines with Unevenly Distributed Split Teeth," IEEE Transactions on Industry Applications, vol. 58, no. 4, pp. 4637-4647, July-Aug. 2022.
In recent years, bi-directional magnetic field modulation (BD-MFM) motors have attracted considerable attention, due to their inherent advantage of high torque density. However, the bi-directional magnetic field modulation structure often leads to unavoidable high torque ripple and flux leakage[1]-[2]. Therefore, it has been a challenge issue on how to further reduce the torque ripple of BD-MFM motors while maintaining the high torque. In this paper, a novel trapezoidal-shaped PM BD-MFM motor is proposed, the contribution of the proposed motor is presented as follows. Firstly, the relationship among the cogging torque harmonics, airgap flux harmonics, and torque harmonics is investigated. Then, the magneto-motive force of the stator permanent magnets is investigated in detail considering stator PM topology. Finally, to minimize magnetic leakage and cogging torque, the trapezoidal PM structure and rotor magnetic barrier are designed. It provides an effective research path to realize the low-torque-ripple design of BD-MFM motors. Fig. 1(a) illustrates the structures of the proposed trapezoidal PM BD-MFM motor, the reference BD-MFM motor I, and the reference BD-MFM motor II. The reference motor and the proposed motor have the same structure size and permanent magnet dosage. Fig. 1(b) shows the modulation process of the stator-PM MMF and rotor-PM MMF respectively. Fig. 2(a) shows the comparison of the magnetic field distribution and leakage analysis between the proposed trapezoidal PM BD-MFM motor and the reference BD-MFM motor II, and it can be found that the magnetic flux leakage at the airgap is significantly reduced. Fig. 2(b)-(d) shows the comparison results of electromagnetic performances of three motors, including cogging torque, airgap flux density, and output torque. It is noted that the proposed trapezoidal PM BD-MFM motor torque is increased by 4.9 Nm and the torque ripple is reduced by more than 70% which verifies the reasonability and effectiveness of the proposed trapezoidal PM BD-MFM motor. More detailed analysis and experimental verification will be presented in the full paper.References: [1] W. Zhao, Q. Hu, J. Ji, Z. Ling, and Z. Li, "Torque Generation Mechanism of Dual-Permanent-Magnet-Excited Vernier Machine by Air-Gap Field Modulation Theory," IEEE Transactions on Industrial Electronics, vol. 70, no. 10, pp. 9799-9810, Oct. 2023. [2] H. Huang, D. Li, X. Ren, and R. Qu, "Analysis and Reduction Methods of Cogging Torque in Dual PM Vernier Machines with Unevenly Distributed Split Teeth," IEEE Transactions on Industry Applications, vol. 58, no. 4, pp. 4637-4647, July-Aug. 2022.