This article proposes a novel analytical model which combines subdomain method and magnet equivalent circuit (MEC) method to predict the cogging torque of surface-mounted permanent magnet (SPM) motors with rotor eccentricity and magnet defects in any slot-pole combination cases. Firstly, the general solution of open-circuit magnetic field distribution in a slotless SPM motor with magnet defects is derived. Then, the motor is divided into several subdomains along the air-gap circumferential direction to consider the non-uniform air-gap caused by rotor eccentricity, where the air-gap lengths of each subdomain are considered to be uniform. Finally, the methods of conformal mapping and MEC combined with equivalent current is used to consider the effect of slotting and saturation, which is beneficial to improve the calculation precision. The magnetic field distributions and cogging torque calculated by the proposed model are consistent with the results of finite element analysis (FEA). Compared with the FEA, the proposed model can perform fast calculations of air-gap flux density and cogging torque under rotor eccentricity and magnet defects for SPM motors, which can be utilized for optimizing the motor towards fault tolerance.

中文翻译：

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具有转子偏心和磁铁缺陷的表面贴装永磁电机齿槽转矩计算的解析模型

本文提出了一种结合子域方法和磁等效电路 (MEC) 方法的新型分析模型，以预测在任何槽极组合情况下具有转子偏心和磁体缺陷的表面贴装永磁 (SPM) 电机的齿槽转矩。首先，推导出具有磁体缺陷的无槽SPM电机开路磁场分布的一般解。然后，将电机沿气隙圆周方向划分为若干子域，以考虑转子偏心引起的气隙不均匀，其中每个子域的气隙长度被认为是均匀的。最后，采用保形映射和MEC结合等效电流的方法考虑开槽和饱和的影响，有利于提高计算精度。所提出的模型计算的磁场分布和齿槽转矩与有限元分析（FEA）的结果一致。与有限元分析相比，所提出的模型可以快速计算SPM电机转子偏心和磁体缺陷下的气隙磁通密度和齿槽转矩，可用于优化电机的容错性。