Design And Electromagnetic Characteristics Analysis Of High Speed Permanent Magnet Brushless Motor

The permanent magnet brushless motor has the characteristics of small size,high power density and high efficiency,so it is widely used in high-speed processing equipment as a drive motor.However,as the design speed increases,permanent magnet brushless high speed motors face many technical challenges.For example,the rotor eddy current loss is large,and the permanent magnet is easily destroyed due to excessive centrifugal force.In this paper,the permanent magnet brushless high-speed motor is used as the research object to study the technical problems of electromagnetic design,rotor eddy current loss and rotor strength.The main research contents are as follows:Firstly,The electromagnetic scheme of permanent magnet brushless high speed motor is designed.According to the performance requirements of the motor,the electromagnetic scheme is designed by the combination of field and path.The design characteristics of high speed motor are summarized,and the method of designing magnetic load based on core loss is proposed.The static magnetic characteristics,no-load characteristics and load transient characteristics of the motor were analyzed through finite element simulation to ensure the rationality of the motor structure.Secondly,the electromagnetic loss of permanent magnet brushless high speed motor are analyzed.The effects of stator slot number,slot width and permanent magnet pole arc coefficient on rotor eddy current loss of permanent magnet brushless high speed motor are compared and analyzed.In order to reduce the rotor eddy current loss,the mechanical structure of the motor is optimized.By comparing the eddy current losses of the rotor case with three materials,the nickel base alloy material is chosen as the rotor protection sleeve solution.In addition.Structural temperature rise characteristics of permanent magnet brushless high speed motor are analyzed.The stator core loss and copper loss of the motor are calculated by the formula method,and different motor cooling schemes aredesigned according to the losses of each structure.The fluid-solid coupling method was used to simulate the temperature rise of the motor under different cooling schemes.By optimizing the cooling parameters,the structural temperature rise of the motor meets the requirements.At last.The rotor strength of permanent magnet brushless high speed motor is analyzed.In order to prevent permanent magnets from being damaged by high tensile stress caused by high-speed rotation,The rotor adopts a protective sleeve and an interference fit with the permanent magnet,and a spacer block is embedded between the magnetic poles.In order to check the rationality of the rotor structure,the stress distribution of the rotor was calculated by Workbench software.Based on the traditional three-state analysis method,the three-field coupled rotor stress analysis method of magneto-thermal stress field is proposed.Compared with the traditional method,the analysis results obtained by this method are more suitable for the actual situation.The influence of the radial thickness and the interference of the insert material and the sheath on the strength of the rotor is analyzed,which provides the direction for the optimization of the rotor structure.