高速表贴式永磁电机转子强度分析

Rotor Strength Analysis of High-speed Surface Mounted Permanent Magnet Rotors

永磁转子高速运行时,永磁体难以承受离心力引起的拉应力,因此通常在高速永磁转子外装配合金护套保护永磁体,避免永磁体的损坏。为了保证永磁转子在高转速工况下安全运行,必须对护套与永磁体进行强度计算与校核。针对高速转子细长型结构的特点,基于厚壁圆筒理论,推导了高速永磁转子的应变场、位移场和应力场的解析计算公式,并采用有限元法验证了解析计算的正确性。基于推导的解析公式,分析了静态过盈量、护套厚度、转轴材料特性对高速永磁转子强度的影响,总结了高速永磁转子的机械设计规律。以一台额定功率为15k W、额定转速为30000r/min的高速永磁电机为例,给出了高速永磁转子的强度设计方法,为高速永磁转子的机械设计提供了依据。

During high speed operation, permanent magnets （PMs） cannot withstand tensile stress due to the large centrifugal force, and an alloy enclosure is commonly employed to protect the permanent magnets. In order to ensure the safe operation of permanent magnet rotors, it is necessary to calculate the stress in the alloy enclosures and PMs. Because of the slim characteristic of high speed permanent magnet rotors, analytical expressions of stress, strain and displacement were deduced based on the theory of the thick-walled cylinder. The validity of the theoretic analysis was verified by the finite element method （FEM）. Based on the derived analytic expressions, the influences of static interference, the thickness of alloy enclosures and shaft material character on strength were analyzed, and the general design guidelines were derived. Using a high speed PM machine of 30000r/min and 15kW as an example, the design method of high speed PM rotor strength and a basis for protective sleeve design are given.