VP22-09 Power Factor Enhancement Design and Optimization of Variable Leakage Flux Permanent Magnet Motor Considering Driving Cycles
Creators: Xue Zhou
Zixuan Xiang
Publisher: name: IEEE
Year: 2025

I. Introduction Recently, variable leakage flux permanent magnet (VLF-PM) motors have attracted more and more attention in electrical vehicles field due to their merits of high efficiency and high reliability [1]. And yet, due to the uncontrollable leakage flux, the VLF-PM motors suffer from the relatively low power factor at diverse operation conditions, especially at heavy load condition. Hence, how to improve power factor of VLF-PM motors under the complicated operation conditions has become a hot issue. Recently, the spoke-type PM and consequent-pole PM structure are employed to improve air-gap flux density, so as to improve power factor [2]. Yet, the high torque ripple is inevitable. Besides, the current angle of the motor can be increased by designing magnetic reluctance, so as to improve power factor. Yet, the torque reduction is inevitable. In this paper, the design concept of variable-saliency-ratio enhancement is proposed in VLF-PM motor to improve power factor. Moreover, to further improve power factor, the multi-conditions optimization method is employed. II. Power factor enhancement at multiple operation conditions Fig. 1 shows the principle of power factor enhancement of VLF-PM motor considering driving cycles. Obviously, Fig. 1(c) exhibits the relationship between power factor and saliency ratio of VLF-PM motor at various driving conditions. It can be noted that, at low-speed condition, if the positive-saliency-ratio inverse degree KDL+ is lager, the PM flux, the power factor, and output torque can be increased. At high-speed condition, if the negative-saliency-ratio inverse degree KDL- is slightly larger, the current angle and power factor can be increased. III. Motor design and results Fig.2 shows the VLF-PM motor design, optimization and performances validation. Obviously, Fig. 2(a) shows the flux path oriented design of VLF-PM motor for power factor enhancement. It can be seen that, by adding multilayer flux barriers along q-axis, the larger KDL+ and larger KDL- can be realized to improve power factor. Besides, the measured power factor map is shown in Fig. 2(d), and the distribution meets the design demands. More theoretical analysis and experimental results will be presented in the full paper.References: [1] L. Xu et al., “Flux-leakage design principle and multiple-operating conditions modeling of flux leakage controllable PM machine considering driving cycles,” IEEE Trans. Ind. Electron., vol. 69, no. 9, pp. 8862-8874, Sept. 2022. [2] S. Stipetic, D. Zarko and N. Cavar, “Adjustment of rated current and power factor in a synchronous reluctance motor optimally designed for maximum saliency ratio,” IEEE Trans. Ind. Appl., vol. 56, no. 3, pp. 2481-2490, May-Jun. 2020.
I. Introduction Recently, variable leakage flux permanent magnet (VLF-PM) motors have attracted more and more attention in electrical vehicles field due to their merits of high efficiency and high reliability [1]. And yet, due to the uncontrollable leakage flux, the VLF-PM motors suffer from the relatively low power factor at diverse operation conditions, especially at heavy load condition. Hence, how to improve power factor of VLF-PM motors under the complicated operation conditions has become a hot issue. Recently, the spoke-type PM and consequent-pole PM structure are employed to improve air-gap flux density, so as to improve power factor [2]. Yet, the high torque ripple is inevitable. Besides, the current angle of the motor can be increased by designing magnetic reluctance, so as to improve power factor. Yet, the torque reduction is inevitable. In this paper, the design concept of variable-saliency-ratio enhancement is proposed in VLF-PM motor to improve power factor. Moreover, to further improve power factor, the multi-conditions optimization method is employed. II. Power factor enhancement at multiple operation conditions Fig. 1 shows the principle of power factor enhancement of VLF-PM motor considering driving cycles. Obviously, Fig. 1(c) exhibits the relationship between power factor and saliency ratio of VLF-PM motor at various driving conditions. It can be noted that, at low-speed condition, if the positive-saliency-ratio inverse degree KDL+ is lager, the PM flux, the power factor, and output torque can be increased. At high-speed condition, if the negative-saliency-ratio inverse degree KDL- is slightly larger, the current angle and power factor can be increased. III. Motor design and results Fig.2 shows the VLF-PM motor design, optimization and performances validation. Obviously, Fig. 2(a) shows the flux path oriented design of VLF-PM motor for power factor enhancement. It can be seen that, by adding multilayer flux barriers along q-axis, the larger KDL+ and larger KDL- can be realized to improve power factor. Besides, the measured power factor map is shown in Fig. 2(d), and the distribution meets the design demands. More theoretical analysis and experimental results will be presented in the full paper.References: [1] L. Xu et al., “Flux-leakage design principle and multiple-operating conditions modeling of flux leakage controllable PM machine considering driving cycles,” IEEE Trans. Ind. Electron., vol. 69, no. 9, pp. 8862-8874, Sept. 2022. [2] S. Stipetic, D. Zarko and N. Cavar, “Adjustment of rated current and power factor in a synchronous reluctance motor optimally designed for maximum saliency ratio,” IEEE Trans. Ind. Appl., vol. 56, no. 3, pp. 2481-2490, May-Jun. 2020.