Research On Rotor Eddy Current Loss Of High Speed Permanent Magnet Motor

High-speed permanent magnet motor(HSPMM)has the advantages of high efficiency,high power density,compact structure,etc.,and has been widely used in industrial drive,aerospace and other fields.High speed permanent magnet motor has higher power supply frequency and higher power density.However,high-speed permanent magnet motors are generally supplied by inverters.and the air-gap harmonic magnetic field generated by air-gap density distortion caused by current time harmonics and stator grooving will generate eddy current losses on the rotor surface and permanent magnets.Due to the small size of the motor and poor heat dissipation performance,the temperature of permanent magnet may rise too high,resulting in irreversible demagnetization of permanent magnet.Therefore,in-depth analysis of rotor eddy current loss under normal operation of high-speed permanent magnet motor is of great significance to the safe and stable operation of the motor.In this dissertation,120kW surface mounted high speed permanent magnet motor is taken as the research object.Firstly,based on the theory of equivalent current chip model and the basic parameters of the motor structure,the rotor eddy current analytical model of the surface mounted high speed permanent magnet motor is established.At the same time,considering the influence of PWM current harmonic on rotor eddy current loss,the relationship between rotor eddy current loss under rated load and different power supply frequencies is analyzed.Analytical calculation has the advantages of fast and practical,and has certain engineering use value.In order to accurately analyze the generation mechanism of rotor eddy current loss of high speed permanent magnet motor under load,a 2D finite element model of high speed permanent magnet motor is needed.The model takes lmm stainless steel as the jacket.Because the eddy current loss of the rotor yoke is very small,the eddy current loss of the rotor yoke is ignored in the finite element analysis in this paper,and the results of analytical calculation and finite element analysis at different frequencies are compared.At the same time,the finite element model is used to analyze the effect of circumferential section of permanent magnet on the eddy current loss of permanent magnet.According to the improvement of the rotor structure scheme,firstly analyzed the influence of different air gap length on the rotor eddy current loss,are analyzed in the sheath material for austenitic stainless steel,under the condition of different thickness of sheath on the influence of the rotor eddy current loss,and the rotor sheath influence on permanent magnet eddy current density distribution rule is studied.The effect of different sheath materials on the rotor eddy current loss was revealed when the sheath thickness was lmm.and the eddy current density of rotor sheath and permanent magnet,as well as the magnetic density distribution on the surface of sheath and permanent magnet were obtained.