Loss Analysis Of Permanent Magnet Brushless DC Motor

Permanent magnet brushless DC motor is widely used in industry applications,and the required efficiency is higher and higher.With the increase of environmental protection and energy conservation requirements,and the development trend of higher efficiency new energy power,the problems caused by motor loss in industry application attract people’s attention.Copper loss(i.e.resistance loss)and iron loss are the main components of the motor loss,the iron loss is mainly affected by the magnetic field in the motor,as the power component of electromagnetic conversion,the internal magnetic fields of the motor is nonlinear,multi-dimensional and complex,so it is difficult to distinguish and analyze directly in industry applications.The loss will reduces the efficiency of the motor,directly affects the motor performance in application,resulting in energy waste,and the loss will also lead to the heating of the motor,increase the using risk on practical application.Accurate analysis of loss and try to reduce loss is an important link in motor design,so it is necessary to analyze and optimize the motor loss.This thesis briefly introduces the basic structure,loss category,loss generation principle and common calculation method of permanent magnet brushless DC motor.The electromagnetic field finite element analysis model of a 12-pole 9-slot motor used in aerial vehicle is established.Six basic structural features of the motor are simulated by electromagnetic finite element calculation,and then compared and analyzed the simulation results,find out the basic structural features of the motor which can not only minimize the loss but also meet the actual performance requirements.Then,based on the basic structural features of the motor,the magnetization method of the motor magnet is designed,the main magnetizing factors are configured by orthogonal experiment method,and then the magnet magnetization simulation of each combination is carried out to determine the main parameters of the magnet magnetization method with the goal of minimum loss and optimal performance for the motor.After obtaining the basic structural features of the motor and the magnetization method of the magnet,it is necessary to find out the optimal dimension parameters of the motor electromagnetic structure.The loss and performance of motor are simulated by finite element method,and combined with multi-objective genetic algorithm,four key dimensions of magnet thickness,air gap width,stator yoke width and stator tooth width are taken as optimization variables,and the stall torque,loss and torque ripple rate are taken as the optimization target.The range of optimization variables and the optimization target are set according to the actual application requirements,the specific value of the optimal electromagnetic structure dimensions is obtained by genetic algorithm.Finally,based on the optimization results,a loss test experiment is set up to test the loss data by motor coupling loss test method of the actual prototype.Summarize above analysis,the scheme of designed motor on this thesis reducing the motor loss,and the motor performance can meet the design requirements.