摘 要

汽车数目的飞快增长致使石油等化石能源加速消耗，汽车尾气排放引发的环境污染问题也日益突出，因此，新能源汽车早已成为研发重点。永磁同步电机以其高效率、高功率密度、宽运行范围等优点成为车用电机应用的热门，同时这一类电机的大范围应用可以很好地解决资源短缺和环境污染问题。在此背景下，电动汽车用永磁同步电机优化设计方法非常值得研究。

本文旨在探索内置式永磁同步电动机结构参数与性能的关系，结构参数主要包括定转子铁心和永磁体的尺寸，电机性能主要包括电磁性能、温度性能和机械性能；本着不对电机原有结构作过多改变的原则进行优化，因此电机定转子内外径、铁心长度、永磁体尺寸、充磁方向、绕组情况等都不改变。

文中首先概述了近年来电动汽车及电控匹配电机的发展概况，其中丰田Prius电机优化方法体现在文中；继而从永磁电机特性分析和多物理场分析两个角度展开文献综述。

其次，本文简介永磁同步电机的特点，分析并推导了内置式永磁同步电机的齿槽转矩和电磁转矩表达式，对铁耗、空载气隙磁密和空载反电势及其表达式进行了分析。

再次，本文分析永磁电机的边界条件，在平面场用磁矢位建立电机电磁场满足的偏微分方程，并以该方程表示电机的边值问题，继而将该问题等价为能量泛函求极值的问题，推导其数学表达式的离散化方程用以求解电机电磁场参数。

更进一步，本文利用有限元软件Ansys EM对实际电机进行建模、分析，并采用该软件中的Optimization模块分析电机结构参数与电磁性能的关系，结构参数包括定子槽的开口与闭口、定子斜槽及斜槽角度、永磁体内侧转子铁心表面开槽、转子铁心外表面开槽及槽数、槽型、槽的尺寸和位置，电磁性能包括齿槽转矩、电磁转矩、转矩脉动、气隙磁密、反电动势、铁心损耗；选取了定子斜槽7.5机械角度、转子外表面开两个辅助槽、永磁体内侧转子铁心表面开四个辅助槽的优化方案，减少了电机98.9%的齿槽转矩、36%的电磁转矩脉动和6%的铁耗，大幅降低反电动势谐波且不影响电机的机械强度和其他电磁性能。

最后，本文利用温度场分析软件Motor-CAD对实际电机进行建模并分析其稳、瞬态热场，对比了不同条件下电机的温度特性，包括转子铁心开孔与不开孔、采用直槽水道与螺旋槽水道两种情形；在转子铁心开孔、采用螺旋槽水道的基础上根据控制变量法分析电机的冷却性能，变量包括水道圈数、水道横截面尺寸和冷却水流速，在兼顾电机水道机械强度和水道外壳密封性的条件下得到了优化参数，优化后电机各部分的温度下降了20%以上，定子铜耗减少近5%。

关键词：永磁同步电动机；电磁性能；温度性能；齿槽转矩；辅助槽

Abstract

The rapid growth of the number of cars has led to accelerated consumption of fossil energy, such as oil, and the environmental pollution caused by automobile exhaust emissions has become increasingly prominent, therefore, new energy vehicles have long been the focus of research and development. Permanent Magnet Synchronous Motor (PMSM) has become a hot application of automobile motor because of its high efficiency, high power density as well as wide operating range, and the wide application of this kind of motor can solve the problem of shortage of resources and environmental pollution well. Under this background, the optimal design method of permanent magnet synchronous motor for electric vehicle is worthy of study.

The purpose of this paper is to explore the relationship between the structural parameters and properties of the interior permanent magnet synchronous motor. The structural parameters mainly include the size of the stator rotor core and permanent magnet, the motor performance including electromagnetic performance, temperature performance and mechanical properties, in line with the principle that few changes are applied to the original structure, so the permanent magnet size, the magnetic filling direction, the winding condition and so on are unchanged.

In this paper, the development of electric vehicle and electrically controlled matching motor in recent years is summarized, among which the optimization method of Toyota Prius motor is embodied, then the literature review is carried out from two angles of permanent magnet motor characteristic analysis and multi-physical field analysis.

Moreover, this paper introduces the characteristics of PMSM, analyzes and deduces the cogging torque as well as electromagnetic torque expression, and also analyzes the core loss, the empty air gap magnetic density and the no-load anti-EMF with its expression.

Also, this paper analyzes the boundary conditions of the PMSM, establishes the partial differential equation that satisfies the electromagnetic field of the motor by using the magnetic vector potential in the plane field, and uses the equation to represent the boundary value problem of the motor, then makes the problem equivalent to the energy functional extremum, and deduces the discrete equation of its mathematical expression to solve the electromagnetic field parameters.

Furthermore, this paper uses the finite element software Ansys EM to model and analyze the actual motor, and uses the Optimization module in the software to analyze the relationship between the structural parameters of the motor and the electromagnetic performance. The structural parameters are the opening and closing of the stator groove, the stator groove and the oblique groove angle, the surface slotted of the inner rotor core of the permanent magnet, the groove of the outer surface of the rotor core and the number of grooves, the size and position of the groove. Electromagnetic properties include cogging torque, electromagnetic torque, torque pulsation, air gap magnetic density, anti-EMF, core loss. Selecting the optimized design holding the skew stator slot of 7.5 mechanical angle, the rotor outer surface opening two auxiliary groove, permanent magnet inner rotor core surface opening four auxiliary groove optimization scheme, which reduce the motor 98.9% cogging torque, 36% electromagnetic torque pulsation and 6% of the core loss, greatly dismiss the anti-EMF harmonics without affecting the mechanical strength of the motor and other electromagnetic properties.

Finally, this paper uses the temperature field analysis software Motor-CAD to model the actual motor by analyzing its stable and transient thermal field, and compares the temperature characteristics of the motor under different conditions, including the rotor core opening and not opening hole, using the straight groove waterway and the spiral Groove waterway. In the rotor core opening, based on the spiral groove waterway, the cooling performance of the motor is optimized according to the control variable method, variables covering the number of waterway circles, the cross-section size of the waterway and the flow rate of the cooling water. The optimization parameters are obtained under the condition of taking into account the mechanical strength of the motor waterway and the sealing of the waterway shell, the temperature of each part of the motor reduced by more than 20% and the stator copper loss dismissed nearly 5%.

Key Words： Permanent Magnet Synchronous Motor (PMSM)；electromagnetic performance；

temperature performance；cogging torque；auxiliary slot

目 录