Structural Design Optimization Of Permanent Magnet Brushless DC Motor Based On Anisotropic Bonded Magnets

Due to a series of advantages such as small size,light weight and high efficiency,permanent magnet brushless DC motors are widely used in aerospace,medical,computer,home appliances and other fields.Miniature permanent magnet brushless DC motors are developing in the direction of miniaturization,light weight,high speed,high efficiency,low noise,low cost,high reliability,and fast dynamic response,which poses high performance and low cost requirements for magnetic materials,low loss,and the urgent need for diverse shapes.At present,the mainstream of high-performance miniature permanent magnet brushless DC motors adopts sintered Nd-Fe-B materials,which exposes the problems of limited shape,low material utilization rate,high resistivity,and high cost.In some occasions,it is no longer suitable for the development needs of current motors.Anisotropic bonded magnets have the characteristics of high magnetic properties,high material utilization,large degree of freedom in shape,flexible magnetization,and low resistivity,and are expected to replace sintered magnets in the field of micro permanent magnet brushless DC motors.At present,domestic anisotropic bonded magnets have gradually made breakthroughs in magnetic powder preparation,magnet processing and other technologies,but the application research on anisotropic bonded magnets is very weak,lacking systematic design and optimization schemes,and there is a big gap with foreign countries.This paper aims to design a permanent magnet brushless DC motor based on anisotropic bonded magnets based on the characteristics of the material,aiming at the common problems of small output torque,single cogging torque optimization scheme,and high demagnetization risk in the application process.And optimize it,in order to explore the application design optimization scheme suitable for anisotropic bonded magnet materials.The main research work of this paper focuses on the following aspects:(1)The performance and molding characteristics,development status and prospects of anisotropic bonded magnet materials are comprehensively summarized,and the characteristics and development trends of permanent magnet brushless DC motors are briefly introduced.This paper reviews the application research status of anisotropic bonded magnets in permanent magnet brushless DC motors,focusing on the problems of low output torque,high cogging torque,and high risk of demagnetization.(2)This paper briefly analyzes the problems existing in the use of sintered magnets in the current permanent magnet brushless DC motor,and takes a small permanent magnet brushless DC motor as an example to analyze its performance characteristics,and formulate the design goals in combination with the size design requirements.Combined with the performance characteristics of anisotropic bonded magnet materials,the common problems existing in the application of anisotropic bonded magnets are summarized.(3)Using the finite element simulation method,the influencing factors and the influencing laws of the output torque of the permanent magnet brushless DC motor are systematically studied,and the influence of these factors on other performances of the motor is expounded at the same time.Finally,according to the comprehensive requirements of the motor,reasonable design parameters are selected,and a prototype is successfully produced.The test results of the motor characteristics of the prototype show that,compared with the original sintered magnet motor,the optimized design of the anisotropic bonded magnet motor can increase the maximum output torque by 11.07%,increase the maximum efficiency by 3.7%,reduce the total weight by 2.64%,and reduce the rotor weight by 13.57%.(4)Aiming at the problem of cogging torque,a trapezoidal magnetic pole distribution,V-shaped magnet skew,sinusoidal magnetization,unequal-sized magnetic poles,and eccentric pole-shaving structure are proposed to take advantage of the anisotropic bonded magnet material,which has a large degree of freedom in molding and high flexibility in magnetization.The characteristics can effectively reduce the cogging torque without increasing the cost.Using the method of combining finite element and experiment,the influence law of the proposed structure on the cogging torque is systematically studied,the influence on other performances of the motor is explained,and the corresponding design method is given.(5)The steady-state temperature distribution of an anisotropic bonded magnet motor is analyzed by finite element simulation method,and the distribution of high demagnetization risk areas of anisotropic bonded magnets is explored.Innovatively proposed double-layer distributed anisotropic bonded magnets and their design and processing methods.This method can strengthen the local anisotropic bonded magnets,improve the local demagnetization resistance of the anisotropic bonded magnets,and effectively save heavy rare earths.dosage.