VP20-08 A High Torque Density Axial-Flux Permanent Magnet Machine with Yokeless and Segmented Armature
Creators: Litao Dai
Shuangxia Niu
Mingyuan Jiang and Wenjie Wu
Publisher: name: IEEE
Year: 2025

I.Introduction High torque density has been a long-standing pursuit in the field of electric machines, particularly in areas such as electric vehicle and aircraft where smaller sizes and weights are crucial [1]. Axial flux permanent magnet synchronous machines (AFPMSMs) offer higher torque capability compared to radial flux PMSMs due to their larger airgap area within the unit volume. Therefore, AFPMSMs are well-suited for high-torque density applications. To further enhance the torque capability of AFPMSMs with yokeless and segmented armature (YASA), this paper presents a novel skew-spoke YASA AFPMSM. The improved torque capability is attributed to the axial-tilt-placed magnets, which generate a larger rotor flux compared to conventional spoke-type AFPMSM [2]. Consequently, this leads to higher airgap flux density and output torque. II. Proposed Motor Structure Fig. 1 provides a clear visual comparison between the conventional spoke YASA AFPMSM and the proposed skew configuration. Furthermore, Fig. 1 presents a 2D view of the two types of rotors. It is evident that the proposed structure exhibits an increased PM flux. III. Verification Fig. 2 illustrates the electromagnetic torques of the two motors, clearly demonstrating a substantial increase in torque output resulting from using the skew-spoke design. Specifically, the average torque is enhanced from 2.36 Nm to 3.64 Nm through the adoption of a 45-degree skew angle for the PMs. Furthermore, the complete paper will extensively investigate the proposed design method across various skew angles and pole-slot combinations.References: [1] M. Polat, A. Yildiz and R. Akinci, "Performance Analysis and Reduction of Torque Ripple of Axial Flux Permanent Magnet Synchronous Motor Manufactured for Electric Vehicles," in IEEE Transactions on Magnetics, vol. 57, no. 7, pp. 1-9, July 2021, Art no. 8106809, doi: 10.1109/TMAG.2021.3078648. [2] Z. Shi et al., "Design Optimization of a Spoke-Type Axial-Flux PM Machine for In-Wheel Drive Operation," in IEEE Transactions on Transportation Electrification, vol. 10, no. 2, pp. 3770-3781, June 2024, doi: 10.1109/TTE.2023.3310738.
I.Introduction High torque density has been a long-standing pursuit in the field of electric machines, particularly in areas such as electric vehicle and aircraft where smaller sizes and weights are crucial [1]. Axial flux permanent magnet synchronous machines (AFPMSMs) offer higher torque capability compared to radial flux PMSMs due to their larger airgap area within the unit volume. Therefore, AFPMSMs are well-suited for high-torque density applications. To further enhance the torque capability of AFPMSMs with yokeless and segmented armature (YASA), this paper presents a novel skew-spoke YASA AFPMSM. The improved torque capability is attributed to the axial-tilt-placed magnets, which generate a larger rotor flux compared to conventional spoke-type AFPMSM [2]. Consequently, this leads to higher airgap flux density and output torque. II. Proposed Motor Structure Fig. 1 provides a clear visual comparison between the conventional spoke YASA AFPMSM and the proposed skew configuration. Furthermore, Fig. 1 presents a 2D view of the two types of rotors. It is evident that the proposed structure exhibits an increased PM flux. III. Verification Fig. 2 illustrates the electromagnetic torques of the two motors, clearly demonstrating a substantial increase in torque output resulting from using the skew-spoke design. Specifically, the average torque is enhanced from 2.36 Nm to 3.64 Nm through the adoption of a 45-degree skew angle for the PMs. Furthermore, the complete paper will extensively investigate the proposed design method across various skew angles and pole-slot combinations.References: [1] M. Polat, A. Yildiz and R. Akinci, "Performance Analysis and Reduction of Torque Ripple of Axial Flux Permanent Magnet Synchronous Motor Manufactured for Electric Vehicles," in IEEE Transactions on Magnetics, vol. 57, no. 7, pp. 1-9, July 2021, Art no. 8106809, doi: 10.1109/TMAG.2021.3078648. [2] Z. Shi et al., "Design Optimization of a Spoke-Type Axial-Flux PM Machine for In-Wheel Drive Operation," in IEEE Transactions on Transportation Electrification, vol. 10, no. 2, pp. 3770-3781, June 2024, doi: 10.1109/TTE.2023.3310738.