Research On Design And Performance Optimization Asymmetric Variable Leakage Flux Interior Permanent Magnet Motor

Since the 21 st century,the increasing shortage of resources,environmental pollution and other issues have restricted the rapid development of the automobile industry.Electric vehicles have attracted wide attention in the automotive field because of their clean and efficient advantages.Due to the ever-changing operating conditions of electric vehicles,high torque and wide speed regulation are required for their motors.Permanent magnet motor has obvious advantages in efficiency,power density and response speed,so it has become the first choice for electric vehicle driving motor.However,due to the difficulty in adjusting the air gap magnetic field,the speed regulation performance is limited.In recent years,a kind of variable leakage permanent magnet motor has effectively expanded the speed regulation range through the principle of variable leakage.However,the existence of magnetic leakage reduces the peak torque output capacity of the motor,which limits its potential application in the field of electric vehicles.In order to solve the problem of insufficient output torque capacity of traditional variable permanent magnet motor with magnetic leakage,a new type of asymmetric variable leakage variable permanent magnet(AI-VLF-IPM)motor is proposed in this paper.The motor introduces the concept of asymmetric magnetic field offset into the variable leakage motor in order to obtain wide speed regulation and high torque performance at the same time.The motor is designed with asymmetric magnetic barrier and permanent magnet to construct a special permanent magnet loop,which makes the permanent magnet self-leakage and q-axis flux meet to achieve the effect of variable leakage.At the same time,the asymmetric structure is used to approach the maximum angle of reluctance torque and permanent magnet torque,and then the output torque is improved.The main research contents of this paper are as follows:(1)Structure design and principle analysis of AI-VLF-IPM motor.The permanent magnet loop is constructed,so that the self-leakage flux of the permanent magnet meets the q-axis flux,and the effect of variable leakage flux is achieved.At the same time,the concept of magnetic field offset is introduced,which improves the d-axis inductance of the motor,reduces the demagnetization current required in the process of weakening the motor,and further broadens the speed regulation range of the motor.In addition,the asymmetric structure inhibits the decline of q-axis inductance under heavy load,and improves the high-speed loading capacity of the motor.Based on the design of motor magnetic circuit,the principle of realizing variable magnetic leakage and torque improvement of motor is analyzed.(2)The rotor structure optimization of AI-VLF-IPM motor.Firstly,the sensitivity analysis is carried out,and the design variables are divided into high sensitivity layer and low sensitivity layer.Then,a multi-objective optimization model is constructed to weigh the optimal parameters,and the output torque,d-axis inductance and torque ripple are selected as the motor optimization objectives,and finally the final size of the motor is obtained.(3)Electromagnetic performance analysis of AI-VLF-IPM motor.By introducing traditional V-type and symmetrical V-type magnetic leakage variable contrast motors,the back emf,air gap magnetic density,torque performance and efficiency characteristics of the motors are analyzed in detail,and the advantages of asymmetric magnetic leakage variable permanent magnet motors in torque and speed regulation range are verified,which can broaden the efficiency area and enhance the torque output capacity.(4)Experimental verification of AI-VLF-IPM prototype.An asymmetric magnetic leakage variable permanent magnet motor is manufactured.According to the characteristics of the motor,an experimental platform was built to test the characteristics of the motor,such as back emf,variable characteristics of magnetic leakage,torque performance,MTPA trajectory and off-design characteristics.The experimental results are in good agreement with the simulation.