Rotor Strength And Modal Analysis Of High-speed PMSM For Cryopump

High speed permanent magnet motor is widely used in many fields because of its small size,high power density and high efficiency.LNG pump with high speed permanent magnet motor as the core has broad prospects in the natural gas industry.High speed permanent magnet motor has high speed,high linear speed of rotor surface,poor tensile strength of permanent magnet,so the strength problem is particularly important,and slender rotor will reduce the critical speed of rotor,leading to resonance risk in high-speed condition.Especially in the low temperature environment,some rotors have different mechanical characteristics.Therefore,based on a high-speed permanent magnet synchronous motor with rated power of 40 k W and rated speed of35000 r / min for ultra-low temperature pump,this paper carries out the mechanical strength calculation and influence factor analysis of various motor rotor structures,and completes the modal analysis,critical speed calculation and influence factor analysis of high-speed motor rotor Analysis.Taking the electromagnetic and mechanical properties as constraints,the main size parameter range of the rotor is obtained and the parameters are determined.The mathematical calculation model of the rotor strength is deduced and verified by the finite element method,and the stress distribution of the rotor is analyzed.Then,the finite element algorithm is optimized.The influence of interference,rotor speed and temperature on the rotor strength is analyzed and compared.Based on the stress distribution of the shaft section,the weakening end is proposed The stress of the method part.The stress singularity problem often encountered in finite element method is described,and the follow-up results are processed based on this problem.The structural stress of the surface mounted rotor and the built-in rotor with irregular geometry is calculated;the influence of different fillers of three typical materials and the sheath of two typical materials on the strength of the surface mounted rotor is analyzed;and the way to weaken the stress of the built-in rotor is analyzed.According to the main size parameters of the rotor,the shaft is designed,and the free mode and constraint mode of the rotor system are analyzed respectively;the critical speed of the rotor system is calculated by Campbell diagram;the influence of bearing stiffness and damping on the critical speed of the rotor system and the influence of the shaft length are analyzed;the influence of prestress on the critical speed is analyzed based on the above strength calculation.