Analysis On Thermal Stress And Dynamic Of High-speed Permanent Magnet Motor Rotor Based On Thermo-structure Coupling Model

Due to small size,high speed,and direct connection with working machines or loads,high-speed motors are widely used in high-speed machine tools,energy storage flywheels,high-speed centrifuges and compressors.Due to its extremely complex working conditions,it will be affected by stresses such as electromagnetic force,thermal stress and centrifugal force during normal operation.Especially in the overspeed test,the stresses on the rotor and permanent magnets are more serious,and the thermal expansion rate of the rotor material is different.It will inevitably bring about the thermal stess problem of high-speed permanent magnet motors.This topic is to conduct research on such problems.First of all,the paper takes a high-speed surface mounted permanent magnet motor as an example for three methods of thermal stress calculation,its finite element model is established,basic assumptions and boundary conditions are built,stresses distribution under the three algorithms are obtained and their differences are compared.The superiority of the calculation method based on thermo-structure coupling is proved.Secondly,based on the thermo-structure coupling method,for the rotor structure of the high-speed surface mounted permanent magnet machine,the laws of the mechanical strength of the rotor is analyzed.The mechanical strength of the rotor is analyzed,and the influencing factors such as different sleeve thickness and interference on the mechanical strength of the rotor is obtained,and then the rotor sizes selection of high-speed motor is described.Thirdly,for the high-speed interor motor,considering the thermo-structure coupling thermal stress of the interior permanent magnet high-speed motor is calculated based on the finite element method.The mechanical strength and electromagnetic performance of the rotor are studied when the permanent magnets are not segmented or divided into two segments.And the mechanical strength of the V-shaped interor permanent magnet motor’s rotor is studied under different magnetic isolation bridge widths and different permanent magnet included angle.Finally,for the rotor system composed of bearings and rotor,dynamic analysis is analyzed,the influences of different bearing stiffness and rotor sizes on the critical speed are analyzed,and the fatigue life of the shaft is analyzed.