VP6-02 Flux Regulation Capability and Torque Performance Enhancement Design of a New Hybrid-Rotor-Pole Controllable Flux PM Motor
Creators: Wenjie Fan
Xiaoyong Zhu
Lei Xu
Li Quan
Publisher: name: IEEE
Year: 2025

Recently, due to the constant PM magnetic field, the conflict between the wide speed range and high torque density has been a hot issue for PM motors used in electric vehicles (EVs) [1]-[2]. How to broaden the speed range without deteriorating output torque capability has been a research difficulty [3]. To solve the problems, a type of variable flux (VF) PM motors has attracted the attention of scholars, where the PM effective flux can be varied by controlling the PM leakage flux according to the magnitude of the armature reaction [4]. However, due to the increased saturation of the magnetic bridge, the output torque capability of such motors is aggravated and the cogging torque under load is accordingly increased, resulting in a significant increase in the torque ripple compared to traditional PM motors. In this paper, a new hybrid-rotor-pole controllable flux (HRPCF) PM motor is proposed, where the rotor is constituted by two pole units for the objective of realizing the synchronous improvement of the flux-weakening capability and output torque. Meanwhile, through the special notch design of the rotor surface, the torque ripple of such motors can be also effectively reduced. Fig. 1(a) shows the topology of the motor, which is separated into the variable flux pole (VFP) unit and non-variable flux pole (NVFP) unit in Fig. 1(b), the VFP unit realizes the flux regulation while NVFP unit ensures the output torque. Fig. 1(c) shows the ideal air gap flux density, due to the notch design, the resulting position and angle of the saturation region are both varied. In Fig. 2(a), the variation of the d-axis flux linkage is compared with a traditional VF-PM motor with the same PM consumption. It shows the proposed motor not only exhibits a higher value of flux linkage at a rated current but also a wider flux variation range. The torque performance in Fig. 2(b) verifies that the notch design can significantly suppress the torque ripple. Finally, the prototyped motor is manufactured, the no-load back-EMF is tested and agreed with the simulated results in Fig. 2(d). In addition, the transient response indicates that the motor possesses a quick response and can satisfy the multiple operating conditions for EV applications.References: [1] Y. Tang, F. Chai and et. al., IEEE Transactions on Industrial Electronics, Vol. 70, no. 7, pp. 6574-6584 (2023) [2] X. Zhao, S. Niu and et. al., IEEE Transactions on Industrial Electronics, Vol. 68, no. 7, pp. 6075-6086 (2021) [3] Y. Du, Y. Mao and et. al., IEEE Transactions on Transportation Electrification, Vol. 8, no. 2, pp. 2479-2489 (2022) [4] L. Xu, X. Zhu and et. al., IEEE Transactions on Industrial Electronics, Vol. 69, no. 9, pp. 8862-8874 (2022)
Recently, due to the constant PM magnetic field, the conflict between the wide speed range and high torque density has been a hot issue for PM motors used in electric vehicles (EVs) [1]-[2]. How to broaden the speed range without deteriorating output torque capability has been a research difficulty [3]. To solve the problems, a type of variable flux (VF) PM motors has attracted the attention of scholars, where the PM effective flux can be varied by controlling the PM leakage flux according to the magnitude of the armature reaction [4]. However, due to the increased saturation of the magnetic bridge, the output torque capability of such motors is aggravated and the cogging torque under load is accordingly increased, resulting in a significant increase in the torque ripple compared to traditional PM motors. In this paper, a new hybrid-rotor-pole controllable flux (HRPCF) PM motor is proposed, where the rotor is constituted by two pole units for the objective of realizing the synchronous improvement of the flux-weakening capability and output torque. Meanwhile, through the special notch design of the rotor surface, the torque ripple of such motors can be also effectively reduced. Fig. 1(a) shows the topology of the motor, which is separated into the variable flux pole (VFP) unit and non-variable flux pole (NVFP) unit in Fig. 1(b), the VFP unit realizes the flux regulation while NVFP unit ensures the output torque. Fig. 1(c) shows the ideal air gap flux density, due to the notch design, the resulting position and angle of the saturation region are both varied. In Fig. 2(a), the variation of the d-axis flux linkage is compared with a traditional VF-PM motor with the same PM consumption. It shows the proposed motor not only exhibits a higher value of flux linkage at a rated current but also a wider flux variation range. The torque performance in Fig. 2(b) verifies that the notch design can significantly suppress the torque ripple. Finally, the prototyped motor is manufactured, the no-load back-EMF is tested and agreed with the simulated results in Fig. 2(d). In addition, the transient response indicates that the motor possesses a quick response and can satisfy the multiple operating conditions for EV applications.References: [1] Y. Tang, F. Chai and et. al., IEEE Transactions on Industrial Electronics, Vol. 70, no. 7, pp. 6574-6584 (2023) [2] X. Zhao, S. Niu and et. al., IEEE Transactions on Industrial Electronics, Vol. 68, no. 7, pp. 6075-6086 (2021) [3] Y. Du, Y. Mao and et. al., IEEE Transactions on Transportation Electrification, Vol. 8, no. 2, pp. 2479-2489 (2022) [4] L. Xu, X. Zhu and et. al., IEEE Transactions on Industrial Electronics, Vol. 69, no. 9, pp. 8862-8874 (2022)