VP3-04 The Structure Improvement Method and Analysis Based on the Characteristics of Motor Magnetic Field
Creators: Xiaoyu Liang
Mingqiao Wang*
Yong Liu*
Ping Zheng and Jialin Gao
Publisher: name: IEEE
Year: 2025

With high-power, high-torque density, permanent magnet (PM) synchronous motor (PMSM) is widely used as torque motor and drive motor. The higher energy-density motor can save more space for other structures in these fields. Many scholars have proposed different structural improvement schemes from the aspects of Pole-Slot combination and PM form for this [1, 2]. In the closed magnetic field inside the motor, it can be divided into the airgap magnetic field for direct electromechanical energy conversion, which is intersected by the windings; the "connecting" magnetic field, which ensures magnetic field closure, is mainly located in the yoke. If a stronger airgap magnetic field can be achieved with less flux connection structure, the energy density will be improved. Different types of motors have different magnetic field characteristics, which determine how to improve the original structure. The magnetic field distribution of the integer slot distributed winding (ISDW, such as 24S4P) and fractional slot concentrated winding (FSCW, such as 24S20P) motor under no load are shown in Fig. 1 as example. The number of parallel magnetic circuits of 24S20P motor is larger, and the required yoke is narrower, however there are more fractional harmonics and zigzag magnetic leakage of tooth. The 24S4P motor requires a wider structure of ‘flux connection’ with lower harmonic content. The above problems limit the further improvement of their performance. The magnetic field distribution of them under load are shown in Fig. 2. The synthetic magnetic field of 24S4P motor is stronger than that of 24S20P motor, and the magnetic field especially at rotor is shift due to the larger armature inductance and other factors. Based on the analysis, the flux connection structure of the FSCW motor can be harmonic-oriented designed to suppress invalid harmonics and ensure fundamental harmonic. The ISDW motor can shift PM and armature magnetic field, and change their superposition relationship to reduce saturation.References: [1] H. Chen, N. A. O. Demerdash, and A. M. EL-Refaie, "Investigation of a 3D-Magnetic Flux PMSM With High Torque Density for Electric Vehicles," IEEE Transactions on Energy Conversion, vol. 37, no. 2, pp. 1442-1454 (2022) [2] Y. Du, Chen Xu, and Feng Xiao, "Low Harmonics Design for Modular Permanent Magnet Synchronous Machine Using Partitioned Winding," IEEE Transactions on Industrial Electronics, vol. 69, no. 9, pp. 9268-9278 (2022)
With high-power, high-torque density, permanent magnet (PM) synchronous motor (PMSM) is widely used as torque motor and drive motor. The higher energy-density motor can save more space for other structures in these fields. Many scholars have proposed different structural improvement schemes from the aspects of Pole-Slot combination and PM form for this [1, 2]. In the closed magnetic field inside the motor, it can be divided into the airgap magnetic field for direct electromechanical energy conversion, which is intersected by the windings; the "connecting" magnetic field, which ensures magnetic field closure, is mainly located in the yoke. If a stronger airgap magnetic field can be achieved with less flux connection structure, the energy density will be improved. Different types of motors have different magnetic field characteristics, which determine how to improve the original structure. The magnetic field distribution of the integer slot distributed winding (ISDW, such as 24S4P) and fractional slot concentrated winding (FSCW, such as 24S20P) motor under no load are shown in Fig. 1 as example. The number of parallel magnetic circuits of 24S20P motor is larger, and the required yoke is narrower, however there are more fractional harmonics and zigzag magnetic leakage of tooth. The 24S4P motor requires a wider structure of ‘flux connection’ with lower harmonic content. The above problems limit the further improvement of their performance. The magnetic field distribution of them under load are shown in Fig. 2. The synthetic magnetic field of 24S4P motor is stronger than that of 24S20P motor, and the magnetic field especially at rotor is shift due to the larger armature inductance and other factors. Based on the analysis, the flux connection structure of the FSCW motor can be harmonic-oriented designed to suppress invalid harmonics and ensure fundamental harmonic. The ISDW motor can shift PM and armature magnetic field, and change their superposition relationship to reduce saturation.References: [1] H. Chen, N. A. O. Demerdash, and A. M. EL-Refaie, "Investigation of a 3D-Magnetic Flux PMSM With High Torque Density for Electric Vehicles," IEEE Transactions on Energy Conversion, vol. 37, no. 2, pp. 1442-1454 (2022) [2] Y. Du, Chen Xu, and Feng Xiao, "Low Harmonics Design for Modular Permanent Magnet Synchronous Machine Using Partitioned Winding," IEEE Transactions on Industrial Electronics, vol. 69, no. 9, pp. 9268-9278 (2022)