Design And Optimization Of Ferrite Magnet Synchronous Motor With A Novel Structure Rotor

Due to unstable supply,high prices and irreversible demagnetization at high temperatures of rare earth permanent magnet materials,and the unique advantages of stable supply and low cost of ferrite magnets,ferrite magnet synchronous motors have gradually become an alternative to rare earth permanent magnet synchronous motors,and are widely used in areas such as high-end automotive motors,motorcycle starter motors,power tool motors,household appliances and office equipment.In recent years,the emergence of high-performance ferrite magnet materials has provided a possibility for improving the performance of ferrite magnet synchronous motors.Based on this,ferrite magnet synchronous motors are favored by researchers at home and abroad.This article mainly studies how to improve torque density and anti-demagnetization capability of ferrite permanent magnet synchronous motors.The main contents are as follows:In order to overcome the shortcomings of the low air-gap magnetic density generated by ferrite magnets with the low remanence,this paper proposes a bevelled interior permanent magnet synchronous motor of "V" type structure.Compared with the traditional "V" type structure,the permanent magnets installed in the motor of this structure have a larger volume and the air-gap magnetic density is also larger.First,a 3k W permanent magnet synchronous motor is initially designed,and then a no-load magnetic circuit model is built on the motor to calculate the air-gap magnetic density,and it is verified by finite element simulation.The parameter improvement scheme is obtained through parametric scanning,and the amplitude of the air gap magnetic density reaches 0.6T,which is about 66% to 75% of the magnetic load of the rare earth permanent magnet synchronous motors.It shows that the magnetic loading of the ferrite magnet synchronous motor with bevelled "V" rotor structure can be increased to a higher level.In this paper,the frozen permeability method is used to calculate the d-axis and q-axis inductance.The d-axis and q-axis magnetic circuit model of the armature reaction is established.The parametric scanning is used to analyze the influence of each parameter on the d-axis and q-axis inductance and its difference.And the impact on reluctance torque is indirectly analyzed.It is found by the analysis of the motor torque component that the reluctance torque and its proportion increase with the increase of current,and that the greater the difference between the d-axis and q-axis inductance is,the greater the torque is improved when the load is larger.When the current is lower than the peak current,the proportion of permanent magnet torque is higher than 50%.Aiming at the problem of irreversible demagnetization of ferrite magnet synchronous motors,this paper first establishes a demagnetization model of ferrite magnet,and then analyzes the effects of current and its angle and the various parameters on the rate of irreversible demagnetization.In order to enhance the resistance to irreversible demagnetization,this paper improves the shape of the barrier in the rotor.The results shows that the rate of irreversible demagnetization is significantly reduced after the shape of the barrier is improved.At the same time,the air gap magnetic density and the d-axis and q-axis inductance are reduced.Among them,the air gap magnetic density is greatly affected,and the AC and DC axis inductance is less affected.Finally,the paper uses genetic algorithm to optimize the average torque,torque ripple and irreversible demagnetization rate of the motor.By determining optimal goals,optimal variables and constraints,a mathematical model of optimization design is established,and an optimization flowchart is obtained.The optimization is carried on the joint simulation of MATLAB and Maxwell to optimize.Compared with the original design,the average torque is increased by 23%,the rate of irreversible demagnetization is reduced to 1.4%,and the torque ripple is slightly increased.By analyzing the components of permanent magnet torque and reluctance torque,it is found that after optimization,the component that increases when the current is small is mainly permanent magnet torque,and the component that increases when the current is large is mainly reluctance torque.Thereby the average torque improved under different currents.This shows that the optimization has achieved good results.Compared with the Nd Fe B permanent magnet synchronous motor with the same volume,the torque density of the designed motor reaches 73.4% of the former,and the total cost of the permanent magnet it uses accounts for 6% of the former,indicating that this design motor reduces costs while maintaining a higher torque density.