电动车用轮毂电机的负载磁场解析计算

Analytical Calculation of Loaded Magnetic Field in Hub Motor for Electric Vehicle

为克服有限元分析反复建模复杂、计算耗时耗资源等缺点,提出一种兼顾精度和效率的磁场解析建模方法。以一台48槽16对极的表面嵌入式外转子轮毂电机为研究对象,利用子域技术在二维极坐标系下建立了轮毂电机的负载磁场解析模型。将电机整个求解域划分为定子绕组槽、槽开口、气隙和永磁体转子槽4类子域。根据激励源的不同,分别在不同子域求解矢量磁位的拉普拉斯或泊松方程。利用相邻子域间的边界条件求解各子域的矢量磁位通解,进而得到轮毂电机的磁场分布、反电动势、电感和转矩等电磁性能,并对比分析了开口槽结构的计算结果。通过有限元分析与样机试验验证了解析模型的准确性。在此基础上,进一步研究了极弧系数和槽开口宽度对转矩的影响,结果表明:当该电机的极弧系数为0.825、槽开口角宽度为2.169°时,输出转矩平均值从原样机的160.75 N·m提高至165.08 N·m,转矩脉动率从8.8%降低至3.025%。

To overcome the shortcomings of finite element analysis(FEA),i.e.,tedious iterative modeling and time-and resource-consuming etc.,a magnetic field analytical modeling method is proposed,concurrently considering both accuracy and efficiency.Taking a 48-slot/16-pole pair hub motor with surface-inset external rotor as study object,the loaded magnetic field analytical model of hub motor is established under a 2D polar coordinate system by using subdomain technique.The entire solution domain of the motor is divided into four types of subdomains,i.e.,stator winding slots,slot openings,air gap and permanent magnet rotor slots,and the Laplace’s or Poisson’s equation of magnetic vector potential is solved in different subdomain according to different excitation source.Then,the boundary conditions between adjacent subdomains are used to solve the general solution of the magnetic vector potential in subdomain,and the electromagnetic performance such as magnetic field distribution,back electromotive force,inductance and torque are further calculated,and which with different slot opening structures are compared.FEA and prototype tests are conducted to validate the correctness of analytical models,and on this basis,the effects of polar arc coefficient and slot opening width on torque are further studied.The results show that with a polar arc coefficient of 0.825 and a slot opening angular width of 2.169°,the average output torque increases from original 160.75 N·m to 165.08 N·m,and the torque pulsation rate reduces from original 8.8%to 3.025%.