VP3-06 Optimization of the Magnetic Field of the Main and Auxiliary Poles of a Disc Motor by Analytical Method
Creators: Junhong Wang
Zengjin Xu*
Yang Liu
Zuoxia Xing and Wei Ji
Publisher: name: IEEE
Year: 2025

The amplitude of the air gap flux density will directly affect the back electromotive force waveform of the motor winding, and indirectly affect the output torque and efficiency. In order to increase the amplitude of the air gap flux density and reduce the harmonic distortion rate at the same time, this paper takes the main and auxiliary permanent magnet pole arc ratio as a variable and uses the vector magnetic potential for analytical optimization. The magnetic field formed by the fan-shaped main and auxiliary poles can be equivalent to the magnetic field generated by N linear motors along the radial direction. Assume that the permanent magnet is uniformly magnetized. The relationship between the magnetic induction intensity and the magnetic field intensity in area I as shown in Figure 1 can be obtained. Considering the relative magnetic permeability of the permanent magnet and the additional magnetization vector . The relationship between the magnetic induction intensity and the magnetic field intensity in area II can also be obtained. The magnetization direction of the permanent magnet of the disc motor is different from that of the radial motor. When the external magnetic field is removed, the residual magnetization intensity is still in the axial direction. At this time, the axial residual magnetization intensity can be calculated. Combined with the arc occupied by the main pole permanent magnet and the arc occupied by the auxiliary pole permanent magnet at this time. The vector magnetic potential equation group of areas I and II can be obtained from the Poisson equation. The boundary conditions of regions I and II are introduced to obtain the general solution, and then the axial air gap flux density of region 1 is obtained. The same method can be used to obtain the expression of the air gap flux density on the other side. Finally, finite element verification is performed using Ansys software. The results show that the analytical method is consistent with the finite element method. As shown in Figure 2, the optimal main and auxiliary pole arc ratio increases the air gap flux density of the motor by 9.63% compared with the traditional motor, and the waveform harmonic distortion rate is improved by 13.39%.References: [1] Z. Yue, Z. Sun and Z. Liu, "Design and Magnetic Field Simulation of 3.0T MRI Superconducting Magnet," IEEE Trans. Appl. Supercon., vol. 29, no. 2, pp. 1-6, March 2019. [2] Y. Lu, Y. Yang, M. Zhang, R. Wang, L. Jiang and B. Qin, "Improved Square-Coil Configurations for Homogeneous Magnetic Field Generation," IEEE Trans. Ind. Electron., vol. 69, no. 6, pp. 6350-6360, June 2022.
The amplitude of the air gap flux density will directly affect the back electromotive force waveform of the motor winding, and indirectly affect the output torque and efficiency. In order to increase the amplitude of the air gap flux density and reduce the harmonic distortion rate at the same time, this paper takes the main and auxiliary permanent magnet pole arc ratio as a variable and uses the vector magnetic potential for analytical optimization. The magnetic field formed by the fan-shaped main and auxiliary poles can be equivalent to the magnetic field generated by N linear motors along the radial direction. Assume that the permanent magnet is uniformly magnetized. The relationship between the magnetic induction intensity and the magnetic field intensity in area I as shown in Figure 1 can be obtained. Considering the relative magnetic permeability of the permanent magnet and the additional magnetization vector . The relationship between the magnetic induction intensity and the magnetic field intensity in area II can also be obtained. The magnetization direction of the permanent magnet of the disc motor is different from that of the radial motor. When the external magnetic field is removed, the residual magnetization intensity is still in the axial direction. At this time, the axial residual magnetization intensity can be calculated. Combined with the arc occupied by the main pole permanent magnet and the arc occupied by the auxiliary pole permanent magnet at this time. The vector magnetic potential equation group of areas I and II can be obtained from the Poisson equation. The boundary conditions of regions I and II are introduced to obtain the general solution, and then the axial air gap flux density of region 1 is obtained. The same method can be used to obtain the expression of the air gap flux density on the other side. Finally, finite element verification is performed using Ansys software. The results show that the analytical method is consistent with the finite element method. As shown in Figure 2, the optimal main and auxiliary pole arc ratio increases the air gap flux density of the motor by 9.63% compared with the traditional motor, and the waveform harmonic distortion rate is improved by 13.39%.References: [1] Z. Yue, Z. Sun and Z. Liu, "Design and Magnetic Field Simulation of 3.0T MRI Superconducting Magnet," IEEE Trans. Appl. Supercon., vol. 29, no. 2, pp. 1-6, March 2019. [2] Y. Lu, Y. Yang, M. Zhang, R. Wang, L. Jiang and B. Qin, "Improved Square-Coil Configurations for Homogeneous Magnetic Field Generation," IEEE Trans. Ind. Electron., vol. 69, no. 6, pp. 6350-6360, June 2022.