Development of Universal 3D Equivalent Magnetic Network Model for Yokeless and Segmented Armature Axial Flux Permanent Magnet Motor Using Edge Step Equivalent Method
Jiang Shangxuan, Peng Bing
School of Electrical Engineering Shenyang University of Technology Shenyang 964700 China
Abstract：Due to the advantages of high power density, short end windings, and compact structure, the yokeless and segmented armature (YASA) axial flux permanent magnet motor has become an essential choice for high-performance drive systems such as electric vehicles and aerospace. The equivalent magnetic network (EMN) method considers core saturation and offers a fast calculation speed for determining the magnetic field of an axial flux motor. However, the traditional EMN method cannot accurately estimate the three-dimensional (3D) flux distribution characteristics or fully consider the actual topology of the motor, resulting in an insufficiently accurate initial design scheme. Therefore, this paper proposes a general 3-D EMN model based on edge step equivalent, which provides a fast and precise calculation tool for the initial design of the YASA motor. Firstly, the topology of the stator and rotor structures of the YASA motor is introduced, and the edge-step equivalent EMN modeling method is proposed. This method transforms the complex topology structure into a regular cube network unit by approximately mapping the motor's curved surface to a plane through an equivalent edge step. Thus, the computational complexity caused by the curved surface network unit can be avoided. The YASA motor is divided into the rotor, sliding (including the air gap and the stator tooth top), and stator areas. The 3-D EMN model is established. The sliding area utilizes a hybrid medium network unit to address the dynamic connection issue between the stator and rotor nodes. Secondly, taking a 20-pole 24-slot YASA motor as an example, the traditional model, the edge step equivalent model, and the finite element method (FEM) are compared in terms of air gap flux density, stator tooth flux density, back electromotive force (EMF), and electromagnetic torque. Finally, a YASA motor is manufactured, and its effectiveness is verified through experiments. Compared to the traditional EMN, the edge step equivalent EMN can accurately calculate the 3D magnetic flux distribution and consider the core saturation effect. The relative error of the no-load and load air gap flux density of the edge step equivalent EMN is 2.9% and 3.4%, respectively, significantly lower than those of the traditional EMN. The effective value of the back EMF, measured by the no-load experiment at the rated speed, is 135.62 V, while that calculated by the edge step equivalent EMN model is 136.89 V. Under the rated load condition, the torque calculated by the model is 502.24 N·m, while the measured torque is 478 N·m, resulting in an error of approximately 5.07%. The following conclusions can be drawn. (1) Edge step equivalent EMN obtains a unified network unit, avoids the integral operation, and improves the calculation efficiency. Compared with the traditional EMN model, the calculation speed is improved by 19.1%. (2) The proposed general edge step equivalent EMN model of the YASA motor not only considers the saturation, but also considers the 3-D distribution characteristics of the magnetic flux. The back EMF and torque calculated based on this model are similar to the experimental results, and the calculation accuracy is better than that of the traditional EMN model. (3) The modeling method is universal and can be further extended to other axial flux motors.
蒋尚轩, 彭兵. 边缘阶梯等效的无轭模块化轴向磁通永磁电机通用三维磁网络模型[J]. 电工技术学报, 2026, 41(2): 416-425.
Jiang Shangxuan, Peng Bing. Development of Universal 3D Equivalent Magnetic Network Model for Yokeless and Segmented Armature Axial Flux Permanent Magnet Motor Using Edge Step Equivalent Method. Transactions of China Electrotechnical Society, 2026, 41(2): 416-425.
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2026, Vol. 41 
