Optimum Design And Demagnetization Analysis Of Non-Uniform Air Gap Line-start Permanent Magnet Synchronous Motor

Compared to the ordinary induction motor,line-start permanent magnet synchronous motor(LSPMSM)has significant advantages in high efficiency and high power factor,and compared to the adjust speed permanent magnet synchronous motor it has self starting characteristics,therefore,LSPMSM has a broad prospects of industrial application.However,the air gap magnetic field waveform of ordinary LSPMSM is similar to a square wave,magnetic field is complex.When the motor runs at rated condition,high air gap magnetic field harmonic distortion results in large iron loss,and high electromagnetic noise,thus,it will bring a series of adverse consequences for the motor.In order to solve the problem of complex air gap magnetic field of ordinary LSPMSM,this paper presents a kind of line-start permanent magnet synchronous motor with non-uniform air gap structure.The main research work of this paper is as follows:1.In order to study the air gap structure,the expression of air gap length has been given.Relationship between rotor pole eccentricity and air gap magnetic field is studied by using the magnetic force multiplied by the magnetic field theory.In order to obtain the minimum distortion rate of air gap magnetic field,the eccentricity distance has been optimized.2.Constant air gap is an important part of the non-uniform air gap length function,thus,constant air gap length of the motor is analyzed and designed to meet the design requirements.3.Theoretical analysis and finite element simulation are carried out to study the torque characteristics of the non-uniform air gap motor.The relationship between eccentricity and cogging torque is analyzed to minimize the torque ripple;starting from the main harmonic torque ripple reduction,relationship between EMF harmonics and torque ripple has been studied.4.This paper has studied factors that affect motor demagnetization.Relationship between load torque and moment of inertia between motor demagnetization is studied,and a method for obtaining the minimum working point of permanent magnet is presented.5.Influence of abnormal operating conditions on motors is studied,which provides the basis reasonable design for permanent magnet.Based on the research of the non-uniform air gap LSPMSM,method to suppress magnetic field harmonic has been put out,the pole eccentric method could reduce the cogging torque and torque ripple,and demagnetization rules have been analyzed and summarized.This paper would provide valuable reference for engineering practice.