Study On The Demagnetization Failure Of Surface Mount High Speed Permanent Magnet Synchronous Motor And Local Infiltration Of Heavy Rare Earth

Surface mount high speed permanent magnet synchronous motor is favored by various industries because of its compact structure,high power density,high efficiency and power factor.However,its biggest disadvantage is the large eddy current loss of the magnet,coupled with the limitation of heat dissipation conditions,will cause a large temperature rise of the permanent magnet,and then lead to irreversible magnetic loss of the permanent magnet,which seriously restricts the reliability of continuous operation and service life of the motor.In this paper,the causes of magnet loss of a24 k W surface mount high speed permanent magnet synchronous motor are analyzed,the law of magnet loss is summarized,and the anti-magnetic loss ability of the magnet is improved by the method of selective heavy rare earth infiltration.In this paper,two dimensional and three dimensional finite element calculation models were established respectively to study the formation mechanism and rule of local degaussification of permanent magnets caused by electromagnetic and thermal factors and its influence on the motor performance under the operation condition of high temperature load and high temperature strong demagnetization field.A refined model of local degaussing of a surface attached high-speed permanent magnet synchronous motor was established to study the influence of temperature rise,current and other factors on the depth and area of magnetic degaussing of the magnet during continuous operation after the local degaussing of the motor magnet,and the variation rule of the motor operating performance.On this basis,in the matrix of rare earth magnet,considering the location or subregion of heavy rare earth element infiltration,the region and permeability gradient distribution of local heavy rare earth magnet were finally determined.Under the condition of reducing the use of heavy rare earth element and ensuring the motor performance changes little,the anti-loss ability of the original magnet was similar to that of the original magnet.The electromagnetic force distribution and vibration displacement of the motor are different due to the different variation rules of the air gap magnetic field when the motor has different degrees of magnetization failure.According to the Maxwell tensor method,the temporal and spatial electromagnetic force densities of the normal motor and the motor with different degrees of demagnetization are calculated,and the harmonic characteristics of the spatial distribution and the frequency domain characteristics of the temporal distribution of the electromagnetic force densities under different degrees of demagnetization are obtained.On this basis,the variation of stator external surface vibration displacement along the x,y and z axes of the normal motor and the motor with different degrees of demagnetization failure are analyzed and compared.The results show that the demagnetization failure of the magnet will lead to the intensification of motor vibration.