Accurate calculation of magnetic field distribution is a prerequisite for motor design and optimization. This article develops an analytical subdomain model of external rotor in-wheel motor with surface-inset magnets (ERIWMSIMs). Besides, to weaken its torque ripple, an improved topology by integrating magnetic flux modulation slots (MFMSs) into tooth tips is proposed. First, the entire field problem is divided into five subdomains, viz., magnet rotor slots, air gap, stator slots, stator slot openings, and MFMSs. Then, this study solves Laplace’s or Poisson’s equation of magnetic vector potential in each subdomain according to the type of excitation source and use the boundary conditions of adjacent subdomains to determine the magnetic field solution. Consequently, the electromagnetic performances such as air gap flux density, back electromotive (EMF), cogging torque, and on-load output torque are accurately predicted. The analytical results are shown in line with those obtained from finite-element analysis (FEA) and experimental results. Furthermore, the influence of MFMS parameters on the torque is further investigated. When double MFMSs are integrated into each tooth tip, the depth of the MFMS is 0.7 mm, and the width is 1.05 times the slot opening; the results demonstrate that the torque ripple can be essentially weakened compared with other topologies.

中文翻译：

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面嵌式永磁轮毂电机解析计算及转矩脉动减小

精确计算磁场分布是电机设计和优化的前提。本文开发了带有表面嵌入磁铁的外转子轮毂电机 (ERIWMSIM) 的分析子域模型。此外，为了减弱其转矩脉动，提出了一种通过将磁通调制槽（MFMS）集成到齿尖中的改进拓扑。首先，整个场问题分为五个子域，即磁转子槽、气隙、定子槽、定子槽开口和 MFMS。然后，本研究根据激励源的类型求解每个子域中磁矢量势的拉普拉斯或泊松方程，并利用相邻子域的边界条件来确定磁场解。因此，电磁性能，如气隙磁通密度，准确预测反电动势 (EMF)、齿槽转矩和负载输出转矩。分析结果与有限元分析 (FEA) 和实验结果一致。此外，进一步研究了MFMS参数对扭矩的影响。当每个齿尖集成双MFMS时，MFMS的深度为0.7 mm，宽度为槽口的1.05倍；结果表明，与其他拓扑相比，转矩脉动可以从本质上减弱。每个齿尖集成双MFMS时，MFMS的深度为0.7 mm，宽度为槽口的1.05倍；结果表明，与其他拓扑相比，转矩脉动可以从本质上减弱。每个齿尖集成双MFMS时，MFMS的深度为0.7 mm，宽度为槽口的1.05倍；结果表明，与其他拓扑相比，转矩脉动可以从本质上减弱。