Design And Analysis Of High-speed Permanent Magnet Motor Based On Multi-physical Domain Coupling

The advantages of high-speed permanent magnet motors such as high efficiency,high power density and small size make them have a broad application prospect in the fields of national defense and aerospace.However,compared with the traditional low and medium speed motors,the coupling between the electromagnetic field,temperature field and stress field inside the high-speed permanent magnet motor is more serious.Meanwhile,the current traditional design method of high-speed permanent magnet motor based on finite element has the problems of long time and difficult coupling,which makes it difficult to quantify the influence relationship between the parameters of the motor.For this reason,this paper proposes an efficient design method for high-speed permanent magnet motors based on magnetic-thermal-strength-dynamics multi-domain coupling,builds a multi-physics domain coupling model for this type of motor,quickly and accurately establishes the influence of each design parameter on the electromagnetic,temperature,rotor strength and dynamics parameters of the motor,and accelerates the design development of high-speed permanent magnet motors.The related research work mainly includes:First,for the problem of time-consuming analysis of electromagnetic and thermal calculations of high-speed permanent magnet motors based on traditional finite elements,a fast analysis model of electromagnetic and temperature rise based on the analytical method is proposed.According to the magnetic field distribution characteristics of high-speed permanent magnet motor,the electromagnetic design model of high-speed permanent magnet motor based on magnetic path method is established.Based on the analysis of the heat transfer path of high-speed permanent magnet motor,a multi-node heat transfer model of high-speed permanent magnet motor based on the total set parameter thermal network method is constructed,and the temperature rise distribution law of high-speed permanent magnet motor is obtained.On this basis,the validity of the established electromagnetic and thermal models is verified by taking a 20 k W,100 krpm high-speed permanent magnet motor as an example.Then,for the problems of long time for the traditional FEM-based rotor strength and dynamics analysis of high-speed permanent magnet motor,and the difficulty of coupling with electromagnetic and temperature fields,a fast analysis model of rotor strength and dynamics based on the thick-walled cylinder principle and transfer matrix method is adopted.According to the fitting relationship of each layer of the high-speed PM motor rotor,an analytical method based on the high-speed PM motor rotor interference fitting model is established to obtain the rotor stress distribution law when the rotor adopts alloy sheath and carbon fiber sheath respectively in different working conditions.Based on the analysis of the state vector transfer law between rotor sections of high-speed permanent magnet motor,a high-speed permanent magnet motor aggregate parameter dynamics model is established,and the influence law of bearing support stiffness on the critical rotor speed of high-speed permanent magnet motor is obtained.On this basis,the validity of the two analytical models is verified by taking a 20 k W,100 krpm high-speed permanent magnet motor as an example.As a result,the solution method for the optimum sheath thickness and interference amount,and the reasonable selection criteria for the rotor bearing stiffness are clarified.Next,based on the characteristics of the aforementioned single physical domain analytical model,the coupling mechanism between electromagnetic,thermal,strength and kinetic parameters of the high-speed permanent magnet motor is analyzed,so that a coupled electromagnetic-thermal-strength-kinetic analytical model of the high-speed permanent magnet motor is established,and the influence laws of the main parameters on the electromagnetic performance,temperature rise distribution,rotor stress and critical speed of the motor are obtained.On this basis,sensitivity analysis and multi-objective optimization strategy under multivariate and multi-constraint are introduced to optimize the design of the20 k W,100 krpm high-speed permanent magnet motor,and its final design scheme is obtained,and the motor performance under the final scheme is validated.Finally,based on the established electromagnetic-thermal-strength-dynamic coupling model of high-speed permanent magnet motor,a software platform is developed for efficient design of high-speed permanent magnet motor using Matlab to facilitate rapid design of high-speed permanent magnet motor of the same type.