Temperature Field And Strength Analysis Of High-Speed Permanent Magnet Motors With Different Sleeve Materials And Structures

High-speed permanent magnet motor is famous for high efficiency,high speed and high power density,which has a wide range of applications in industrial manufacturing,aerospace and other fields that have special requirements for motor size and volume.This paper takes the high-speed permanent magnet motor as the research object,begins with the rotor sleeve materials and structures,and explores the influence of them on the rotor eddy current loss,rotor strength and temperature field.The main research contents are as follows:Firstly,the characteristics and requirements of rotor design are described from the aspects of electromagnetism,temperature and stress fields.And the rotor sleeve selection and design process considering the electromagnetic field,temperature field,stress field and thermal-stress coupling is proposed comprehensively.A 150 k W,40000r/min high-speed permanent magnet motor is designed,and the sleeve material is titanium alloy.To meet the air-gap flux density of the motor as the limitation of the electromagnetic performance on the rotor structure,another high-speed permanent magnet motor with the same specification of carbon fiber as the sleeve material is designed.It provides reference for the selection and design of sleeve material and structure from the perspective of electromagnetic performance.Secondly,in view of the large centrifugal force brought about by the high rotational speed of the motor rotor and the large thermal stress brought about by the high temperature,the strength check must be carried out.The three-dimensional stress analytical model of the motor rotor is established.Considering the axial stress,the analytical formula of the k-layer rotor structure under the isotropic sleeve material is given,and compared to verify the validity of the analytical method.The anisotropic carbon fiber composites are analyzed by the method of simulating carbon fiber winding.The radial,tangential and axial stress values of the permanent magnets in the axial fiber direction and circumferential fiber direction are compared and analyzed.The conditions of rotor failure are summarized.The influence of factors such as rotational speed,temperature,and inner and outer interference fitting on the stress of the permanent magnet and the sleeve is analyzed,and the corresponding laws are summarized.A design principle of the multi-layer sleeves structure is summarized.It provides reference for the selection and design of sleeve material and structure from the perspective of rotor strength.Then,in view of the problem that large rotor eddy current loss and increased rotor temperature.According to the principle of eddy current loss generation,the eddy current density and eddy current loss values under different sleeve structures are compared and analyzed.The eddy current loss ratio of each part of the rotor under different copper layer thicknesses is analyzed.Other losses such as motor copper loss,iron loss,rotor eddy current loss and wind friction loss are calculated.The influence of the thermal conductivity of air gap on the temperature of the stator and rotor is studied,and the formula of the equivalent thermal conductivity of the variable air gap is deduced.The 3-D temperature field analysis model is established.The temperature distribution of the rotor under different sleeve structures and copper layer thicknesses is analyzed by finite element analysis method.And summarizing the corresponding rules.It provides reference for the selection and design of sleeve material and structure from the perspective of rotor eddy current loss and temperature field.Finally,according to the results of the temperature field analysis,the appropriate sleeve structure is selected respectively.The size of the inner and outer interference fitting is the input variable,the stress of the rotor is the output variable,and the orthogonal test data is established.Taking the failure condition of the rotor as the constraint,taking minimize the amount of interference fitting as the goal,the method of parametic scanning is used to determine the size of the inner and outer interference fitting under the two structures based on the finite lelment analysis,and give the rotor stress distribution.It provides a reference for the selection and design of sleeve material and structure from the perspective of thermal-stress coupling.