Permanent Magnetic Torque Optimization Of Hybrid Magnetic Circuit Double Permanent Magnet Motor

In recent years,with the rapid increase use fuel vehicles and the contradictions between environmental pollution and energy crisis,new energy vehicles have attracted considerable attention.And rare earth permanent magnet motor have been widely applied as driving motors of electric vehicles,due to its inherent advantages of high torque/power density and high efficiency.However,as an important strategic resource,rare earth material has some unstable factors such as supply chain and price,which will hinder the rapid development of modern electric vehicles to some extent.Therefore,it is very necessary to so effectively reduce the dependence of electric vehicle driving motors on rare earth permanent magnet materials.Consequently,it has been a hot but challenging issue on how to research less rare earth permanent magnet motor with high torque high torque density,high efficiency.In this paper,in order to achieve higher torque density and effectively reduce the use of rare earth permanent magnet materials,a double permanent magnet motor with the characteristics of“Nd Fe B+ferrite” coordinated excitation is proposed.Moreover,by combining the design concept of "asymmetric magnetic circuit" with the topology of hybrid permanent magnet,asymmetric permanent magnet rotor topology is formed,which aims to effectively improve the utilization ratio of permanent magnet magnetic field of motor.Among them,the main research contents are presented as follows:First of all,the development of new energy electric vehicles is reviewed,and the research status of rare earth motors is summarized.According to the overall design requirements of electric vehicles,the structural parameters of the motor,the parameters of the stator slot and the ratio between poles and slots are preliminarily determined.Meanwhile,the preliminary structure schemes of the hybrid magnetic circuit double permanent magnet motor under the combination of9-slots-6-poles and 12-slots-10-poles are built.Secondly,in order to improve the utilization rate of permanent magnet magnetic field,an asymmetric permanent magnet rotor topology based on “Nd Fe B+ferrite” is proposed.In order to study the composition of different permanent magnet torque,the frozen permeability method is used to separate Nd Fe B torque and ferrite torque effectively.Moreover,the design concept of "maximum torque approximation" with different permanent magnet torque components is put forward,and the effective approximation between permanent magnet torque components is realized by asymmetric design of Nd Fe B magnetic circuit and ferrite magnetic circuit in order to obtain the design effect improving the motor permanent magnet magnetic field utilization rate.In addition,electromagnetic performances of these two kinds of motor structure design are analyzed and compared including torque characteristics,magnetic field distribution,no-load characteristics,loss and efficiency by using the finite element method.The analysis shows that the permanent magnet torque utilization ratio of 12-slots-10-poles hybrid magnetic circuit double permanent magnet motor is higher.In addition,this motor has the advantages of low loss,high efficiency and strong stability,so it is selected as the prototype of the final experimental processing.Finally,the 12-slots-10-poles hybrid magnetic circuit double permanent magnet motor is built,and the experimental analysis is carried out based on experimental platform.By testing the characteristics under no-load,steady-state and dynamic condition,the rationality and feasibility of the design and analysis of the hybrid magnetic circuit double permanent magnet motor are verified.