Research On Electromagnetic And Thermal Performance Of Interior Permanent Magnet Synchronous Motor Based On Lumped Parameter Method

Interior permanent magnet synchronous motor（IPMSM）has been widely used in the fields electric vehicles because of its high torque density and low eddy current loss of permanent magnets.Lumped parameter method is one of the commonly used motor analysis methods.It can consider the nonlinear saturation of IPM motor and quickly analyze the electromagnetic performance or thermal performance of the motor parametrically.At the same time,it has good calculation accuracy and has been widely used in the initial design stage of IPM motor.At present,the research on lumped parameter models at home and abroad mainly includes equivalent magnetic network,EMN)model and lumped-parameter thermal network（LPTN）model.Based on these two lumped parameter models,this paper will study the electromagnetic performance and thermal performance of automotive IPM motors.Firstly,to solve the problem that the traditional EMN model is not accurate enough to calculate the air gap flux density of IPM motors with high degree of uneven saturation of magnetic bridges,an improved EMN model is proposed in this paper.On the basis of analyzing the mechanism of uneven saturation of magnetic bridge between poles of IPM motor,it is divided into four sub-regions.According to the geometric structure of each sub-region and the trend of magnetic field lines,the corresponding multi-segment nonlinear permeability units are built to consider the uneven saturation and saturation deviation of magnetic bridge.Taking a vehicle IPMSM as an example,the electromagnetic performance of the motor is calculated by using the proposed model,and the calculated results are compared with the traditional EMN model,FEA results and experimental results to verify the proposed model.In addition,this paper also analyzes the applicable scope of the improved EMN model.Secondly,aiming at the problem that there are a lot of space harmonics of magnetomotive force in the air gap of IPM motor for vehicles,a magnetic barrier structure for improving the electromagnetic performance of the motor is proposed.In order to make the magnetic barrier structure added in the rotor not affect the rated output torque of the motor,Taguchi method is used to optimize the structural parameters of the magnetic barrier.Aiming at the limitation that Taguchi method can only find the optimal scheme within the range of the level of optimization factors,EMN model is used to select the initial values of the structural parameters of magnetic barriers to improve the optimization effect of the final scheme.In addition,the influence of magnetic barrier structure parameters on the electromagnetic performance of the motor is analyzed.Finally,to solve the problem that the conventional LPTN model can’t take into account the reaction of temperature rise caused by the change of electromagnetic characteristics of the motor,a magnetothermal coupling calculation scheme of IPM motor combining EMN method and LPTN method is proposed,and the temperature rise characteristics of the motor are calculated.In order to verify that the calculation accuracy of the magnetic-thermal coupling method of motor temperature field is higher than that of conventional LPTN method,the calculation results of magnetic-thermal coupling,conventional LPTN method,FEA and experimental results are compared.