Research On Influence And Weakening Method Of Core Saturation Of Electric Vehicle Permanent Magnet Synchronous Motor

The consumption of fossil fuels is an important source of air pollution.It is urgent to develop new energy vehicles with low and zero exhaust emissions,which brings new development opportunities and challenges to the traditional automobile industry.Major automobile manufacturers in the world have started to research and develop related technologies of electric vehicles.The permanent magnet synchronous motor(PMSM)for electric vehicles has become the focus and research focus of the industry owing to the merits of high power and torque density,high efficiency,good demagnetization withstand capability,as well as high stability and anti-interference ability.However,in the flux weakening region and low speed high torque condition,the saturation of the electric vehicle driving motor core reduces the performance of the motor.Firstly,the technical requirements and structural characteristics of PMSM used in electric vehicles are introduced.The research status and analytical method of iron core saturation in electric vehicle driving motor are summarized.According to the design requirements,the stator structure,rotor structure and air gap length of the 8-pole 18-slot,8-pole 36-slot fractional slot PMSM and 8-pole 48-slot integer slot PMSM are designed.The finite element simulation software Ansoft was used to build the motor model,and the simulation analysis was carried out on the no-load cogging torque,no-load back electromotive force(EMF),output torque under rated condition,and the efficiency maps of PMSM with three slot/pole number combinations.The results show that the three kinds of PMSM can satisfy the requirements of basic design.Secondly,the q-axis and d-axis inductances,back EMF and torque ripple in the flux weakening region,the output torque capacity under the condition of low speed and high torque and the core loss of the three kinds of PMSM were simulated and analyzed under considering magent saturation.The results show that back EMF distortion rate and torque ripple of the 8-pole 18-slot PMSM are low in the flux weakening region,and the output torque can be high at low speed and high torque.In the comparison of core loss,when the current Angle is small,the iron loss of the 8-pole 48-slot PMSM is lower,and when the current control Angle is large,the iron loss of the 8-pole 18-slot PMSM is lower.Finally,the same contrast analysis is carried out for the PMSM with complete-pitch winding,Short-pitch winding and long-pitch winding respectively.The simulation results show that the PMSM with short-pitch winding has strongest ability to reduce back EMF distortion rate and torque ripple,the torque output capacity in low speed and high torque condition is between the PMSM with long distance winding and the PMSM with long-pitch winding.In the comparison of core loss,the iron loss of the PMSM with short-pitch winding is slightly higher than the PMSM with long-pitch winding.Considering the overall running stability of electric vehicle drive motor,the performance of PMSM with short-pitch winding is optimal.