High-speed Permanent Magnet Motor Design And Rotor Eddy Current Loss Calculation

High-speed permanent magnet(HSPM)motors are widely utilized owing to their unique advantages including high power density,compact size,and high efficiency in the industrial field.However,there are some characteristics for HSPM motors,such as the large rotor eddy current loss and difficult of heat dissipation compared with conventional motors.This paper proposes a calculation method of rotor eddy current loss for HSPM motors,and the influence of motor structure parameters on eddy current loss is studied.Based on the above analysis,a HSPM motor used in hydrogen fuel cell air compressor is designed.Firstly,a semi-analytical method is proposed to accurately calculate the rotor eddy current loss of High-speed surface-mounted permanent magnet motors.The flux density waveform of each point on the surface of magnet is obtained by two-dimensional finite element analysis(FEA),and the eddy current loss of magnet can be calculated according to the analytical formula based on the flux density obtained by FEA.The results obtained by the proposed method is in good agreement with that of three-dimensional FEA,which verifies the effectiveness of the method.Secondly,the parameter affecting the eddy current loss of HSPM motors are studied.The effects of air gap length,magnet segmentation,sleeve segmentation,slot width,sleeve thickness,and sleeve material on the rotor eddy current loss are calculated by FEA.Based on the above analysis,a method to reduce the rotor eddy current loss by using a composite sleeve is proposed.The composite sleeve is composed of two materials,in which the outer layer is made of carbon fiber,and the inner layer is made of titanium alloy.The effectiveness of the composite sleeve in suppressing eddy current loss is verified by FEA.Finally,a HSPM motor with a rated power of 10 k W and a rated speed of 100000 r/min is designed.The no-load and load characteristics of the motor are calculated,and the stress and temperature rise are also analyzed.The calculation results show that the stress and temperature rise of the motor are within the material safety range,which proves the correctness of the motor design method.