Research On Magneto-thermal Coupling Analysis And Structural Multi-objective Optimization Design Of Permanent Magnet Synchronous Motor

As a key component of new energy vehicles,the motor directly affects the power,economy,and life of new energy vehicles.Among them,permanent magnet synchronous motor(PMSM)is widely used in new energy vehicles because of its simple structure,rapid response,reliability,and high efficiency.However,the complex working environment and poor heat dissipation of PMSM lead to serious heat generation in the motors.Excessive temperature may lead to the failure of the insulation layer of the stator winding and the silicon steel sheet,permanent demagnetization of the permanent magnets,and other problems,and affecting the motor performance.Therefore,it is necessary to analyze the temperature field characteristics and structural optimization design of PMSM.The magnetic field characteristics,temperature field characteristics,and structural optimization design of a 6-pole 36-slot PMSM need to be explored in depth.The main content are divided into three parts as follows:(1)The simulation model of magnetic field and the analysis of magnetic field characteristics of PMSM.The 2D simulation model of motor is established by Maxwell software.The transient magnetic field of the motor under no-load and load conditions is simulated and studied,including the analysis of flux density and the magnetic line,the analysis of counter electromotive force under no-load conditions,the analysis of air gap magnetic density and torque characteristics,and so on.The results of the simulation show that the magnetic field distribution of the motor is reasonable,the waveform of counter electromotive force under no-load conditions and air-gap radial magnetic density is good,and the analysis of FFT is also stable.The stator core loss,copper loss,and permanent magnet loss are obtained by simulation,among which the stator core loss and copper loss are relatively large.(2)The magnetic-thermal coupling simulation and the analysis of temperature characteristics under different working conditions of PMSM.A 3D geometric model of the temperature field is established.The material properties and boundary conditions under different operating conditions are set.The loss calculated in the magnetic field is introduced into the simulation model of the temperature field,and the temperature distribution characteristics under different operating conditions are analyzed.The simulation results show that the highest temperature of the motor at peak speed is higher than at rated speed,except for the stator winding and stator core.At different conditions,the stator winding temperature is the highest,the stator core temperature is the second,and the rotor core and permanent magnet temperature are the lowest.(3)Multi-objective optimization design of PMSM structure.With the objective of maximizing the mean torque and minimizing the torque fluctuations and losses,the prediction accuracy of the polynomial response surface(PRS)model,Kriging(Kriging)model,and radial basis neural network(RBF)model is compared.Finally,the PRS model and RBF model are selected.The weight coefficients of each model is calculated by EG method to construct the combined approximate model of each response instead of the finite element simulation model for the deterministic optimization design study.And the temperature characteristics after optimization are analyzed.The results show that the maximum temperature of all major motor components has been reduced after optimization,with a more pronounced reduction in maximum temperature at peak speed.Based on the results of deterministic optimization,the motor is designed for robust optimization,and the optimization results increase compared with deterministic optimization,and the fluctuation of motor performance with uncertainty factors is reduced.In summary,the temperature field of PMSM can be analyzed and simulated more accurately and reasonably by the method of magneto-thermal coupling.To compensate for the limitations of a single approximation model,a combined approximation model instead of a finite element simulation model is proposed for the structural multi-objective optimization design of PMSM,and the results show the effectiveness of the method in achieving the deterministic optimization and robust optimization design of the PMSM structure.