Calculation Of Thermal Stress And Mechanical Properties Of High Speed Permanent Magnet Motor

Owing to the advantages like small size,high speed and direct connection with working machines or loads,high-speed motors are broadly applied in fields including high-speed grinders,energy storage flywheels and high-speed centrifugal compressors.Since rotors are made of different materials with different thermal expansion ratios,rise of rotor temperature will lead to thermal stress.This becomes a concern in calculation of mechanical strength of rotors.Mechanical strength and electromagnetic property of rotors of surface-mounted and built-in type high-speed permanent magnet motors are respectively researched in this subject in consideration of thermal stress.First,the finite element model of a surface-mounted high-speed permanent magnet motor is established and provided with basic assumptions and boundary conditions;contacts of the rotor part are defined,to obtain non-uniform temperature distribution of the rotor part as temperature load leading to thermal stress.Mechanical strength of the rotor is calculated in consideration of thermal stress,and is compared to analytical solution to verify the finite element.Mechanical strength of the rotor under different temperature loads is comparatively analyzed,and influences from thermal expansion ratios and interferences of different permanent magnet structures and shaft materials to mechanical strength of the rotor are analyzed.Second,a built-in high-speed linear motor is calculated on the basis of the finite element in consideration of two stress conditions: thermal stress arising from temperature load and no thermal stress.Mechanical strength and electromagnetic property of the rotor when the linear permanent magnet has two and three segments are also researched.Mechanical strength of the rotor of a V-shaped built-in permanent magnet motor with different flux barriers is researched.Finally,kinetic analysis is conducted to a rotor system composed of a bearing and a rotor,influences of different bearing stiffness and rotor structures to critical speed are researched,and fatigue life of the shaft is analyzed.