VP20-05 Topology Design and Performance Analysis of a New Arch-shaped Magnet Variable Flux Memory Machine
Creators: Wei Liu
Chi Zhang
Jinhua Chen and Yiyi Fu
Publisher: name: IEEE
Year: 2025

I. Introduction Variable flux memory machines (VFMMs) [1]-[2] equipped with low-coercive-force (LCF) PMs are competent for automotive applications. The magnetization states (MSs) of the LCF PMs can be flexibly varied by a current pulse, which can achieve excellent flux adjustability with negligible additional copper loss [3]-[4]. However, existing VFMMs face the challenges of a narrow flux regulation range and significant difficulties in magnetization operation. Thus, this paper proposes a novel arch-shaped magnet VFMM (ASM-VFMM), which can significantly enhance the flux short-circuit effect in the low magnetization state (MS), thereby remarkably improving its flux regulation capability and efficiency in the high-speed region. II. Machine Topology The proposed ASM-VFMM configuration is illustrated in Fig. 1, which features a dual-layer PM arrangement forming an arched structure. An inverted V-shaped PM design is adopted for the first layer, which is closer to the air gap to reduce the difficulty of magnetization operation. The second layer employs a spoke-type PM structure, with an asymmetric PM design increasing the usage of LCF PMs, thus contributing to the enhancement of the flux regulation capability. Furthermore, the high-coercive-force (HCF) PMs in the second layer can form a series magnetic circuit with adjacent or slightly distant LCF PMs, ensuring the on-load MS stability of the VFMM. III. Electromagnetic Performance The electromagnetic characteristics of the ASM-VFMM are shown in Fig. 2. The proposed machine exhibits a substantial decrease in the magnetic field at the low MS compared with that at the high MS. Besides, this machine can achieve over three times the flux regulation range and wide torque variation range through the magnetization operation. Most notably, when shifting from the high MS to the low MS, the high-efficiency region can be shifted from the low-speed region to the high-speed region, indicating that the proposed ASM-VFMM features overall high-efficiency characteristics.References: [1] V. Ostovic, “Memory motors,” IEEE Ind. Appl. Mag., vol. 9, no. 1, pp. 52–61, Jan. 2003. [2] M. A. Darmani et al., “AFPM machines equipped with multilayer magnets,” IEEE Trans. Energy Convers., early access, 2024. [3] R. Tsunata, M et al., “Variable flux memory motor employing double-layer delta-type PM arrangement and large flux barrier for traction applications,” IEEE Trans. on Ind. Appl., vol. 57, no. 4, pp. 3545–3561, Jul. 2021. [4] A. Athavale et al., “Enabling driving cycle loss reduction in variable flux PMSMs via closed-loop magnetization state control,” IEEE Trans. on Ind. Appl., vol. 54, no. 4, pp. 3350–3359, Jul. 2018.
I. Introduction Variable flux memory machines (VFMMs) [1]-[2] equipped with low-coercive-force (LCF) PMs are competent for automotive applications. The magnetization states (MSs) of the LCF PMs can be flexibly varied by a current pulse, which can achieve excellent flux adjustability with negligible additional copper loss [3]-[4]. However, existing VFMMs face the challenges of a narrow flux regulation range and significant difficulties in magnetization operation. Thus, this paper proposes a novel arch-shaped magnet VFMM (ASM-VFMM), which can significantly enhance the flux short-circuit effect in the low magnetization state (MS), thereby remarkably improving its flux regulation capability and efficiency in the high-speed region. II. Machine Topology The proposed ASM-VFMM configuration is illustrated in Fig. 1, which features a dual-layer PM arrangement forming an arched structure. An inverted V-shaped PM design is adopted for the first layer, which is closer to the air gap to reduce the difficulty of magnetization operation. The second layer employs a spoke-type PM structure, with an asymmetric PM design increasing the usage of LCF PMs, thus contributing to the enhancement of the flux regulation capability. Furthermore, the high-coercive-force (HCF) PMs in the second layer can form a series magnetic circuit with adjacent or slightly distant LCF PMs, ensuring the on-load MS stability of the VFMM. III. Electromagnetic Performance The electromagnetic characteristics of the ASM-VFMM are shown in Fig. 2. The proposed machine exhibits a substantial decrease in the magnetic field at the low MS compared with that at the high MS. Besides, this machine can achieve over three times the flux regulation range and wide torque variation range through the magnetization operation. Most notably, when shifting from the high MS to the low MS, the high-efficiency region can be shifted from the low-speed region to the high-speed region, indicating that the proposed ASM-VFMM features overall high-efficiency characteristics.References: [1] V. Ostovic, “Memory motors,” IEEE Ind. Appl. Mag., vol. 9, no. 1, pp. 52–61, Jan. 2003. [2] M. A. Darmani et al., “AFPM machines equipped with multilayer magnets,” IEEE Trans. Energy Convers., early access, 2024. [3] R. Tsunata, M et al., “Variable flux memory motor employing double-layer delta-type PM arrangement and large flux barrier for traction applications,” IEEE Trans. on Ind. Appl., vol. 57, no. 4, pp. 3545–3561, Jul. 2021. [4] A. Athavale et al., “Enabling driving cycle loss reduction in variable flux PMSMs via closed-loop magnetization state control,” IEEE Trans. on Ind. Appl., vol. 54, no. 4, pp. 3350–3359, Jul. 2018.