高速永磁电机转子过盈方式对转子应力的影响

nfluence of Shrink Fitting Modes on Rotor Stress of High Speed Permanent Magnet Machine

该文对高速永磁电机(HSPMM)转子过盈方式对转子应力的影响进行研究。首先,在二维极坐标下建立了转子各部位统一几何模型的应力场数学模型,可求解不同边界条件下转轴、永磁体和护套的径向应力和周向应力。然后,基于建立的应力场数学模型得到不同过盈方式下转子应力的解析计算方法,分析了不同过盈方式对转子应力的影响。在此基础上,提出“虚拟过盈”概念及虚拟过盈下的应力计算表达式,分析了其准确度并解释了其物理意义。最后,通过有限元(FEM)分析方法对一台额定功率为50 kW、额定转速为40000 r/min的高速永磁电机进行分析,说明了不同的过盈方式导致转子应力的差异,验证了理论分析的合理性。

In the design of a high-speed permanent magnet machine,the calculation and verification of rotor stress are very important,especially the stress of a permanent magnet.The existing research mainly focuses on the influence of shrink-fitting magnitude on rotor stress,but ignores the influence of shrink-fitting modes.The shrink fitting between the sleeve and the permanent magnet greatly impacts the rotor stress.Limited by the electromagnetic power,the stress margin left to the permanent magnet or sleeve is limited to improve the material utilization.If the difference of rotor stress under various shrink fitting modes is not considered in the design,the safety of rotor strength will be greatly reduced when the operating point of the machine is near the limit value of the material stress,which may even lead to the failure of the design of high-speed permanent magnet machine.Therefore,the influence of shrink-fitting modes on the rotor stress of high-speed permanent magnet machines should be addressed,and more attention must be paid to it when calculating the rotor stress.This paper studies the influence of shrink-fitting modes on the rotor stress of a high-speed permanent magnet machine.Firstly,the stress field mathematical model of the unified geometric model of each rotor part is established in two-dimensional polar coordinates.The radial and circumferential stresses of the shaft,permanent magnet,and sleeve can be solved under different boundary conditions.It can be concluded that the rotor stress is the sum of the rotational component and the surface pressure component.The tensile stress caused by rotation can be offset by the pressure from the sleeve,and the degree of offset is determined by the pressure applied by the sleeve.Therefore,to calculate the rotor stress accurately,it is necessary to accurately calculate the stress caused by rotation and obtain the pressure applied by the sleeve.It is easy to calculate the stress caused by rotation,while the stress offset by the sleeve pressure is more complicated due to the shrink fitting,so it is necessary to study the influence of shrink-fitting modes on rotor stress.Then,based on the stress field mathematical model,the analytical calculation method of rotor stress under different shrink-fitting modes is further obtained,and the influence of different shrink-fitting modes on rotor stress is analyzed.Finally,taking a high-speed permanent magnet machine with rated power of 50 kW and rated speed of 40000 r/min as an example,the rotor stress under different shrink-fitting modes is calculated by the finite element method.When the magnitude of shrink fitting relative to the sleeve thickness cannot be ignored,different shrink-fitting modes will significantly affect the rotor stress,especially the core component permanent magnet.Therefore,it is necessary to select a better mode by comparing shrink-fitting modes to reduce rotor stress and improve the safety and reliability of the machine.This paper provides theoretical guidance for the design of shrink-fitting modes of high-speed permanent magnet machine rotors.