Research On A Computationally Efficient Method For Calculation Of Magnet Eddy Current Loss In PMSM

With the development of new energy vehicles,permanent magnet synchronous motors(PMSM)are widely used in electric vehicles for their high power density,high efficiency and easy maintenance of the excellent characteristics.Due to the structural parameters and the control method of PMSM,the magnetic field inside the motor is distorted.This will cause a serious permanent magnet eddy current loss in the permanent magnet,which is an important consideration in the design of the motor.However,there is no computationally efficient calculation method for magnet eddy loss.In this paper,taking the surface-mounted PMSM as the research object and considering the motor control mode,a computationally efficient method for calculation of magnet eddy current loss over the entire torque-speed envelope in PMSM for electric vehicles is proposed.Firstly,based on the motor open-loop control and the closed-loop vector control algorithm,the control model of permanent magnet synchronous motor is established,and the stator phase current in the whole working area of the motor is analyzed.Through the Fourier analysis,the effects of different motor control parameters on phase current time harmonic is derived,including PWM ratio,carrier ratio,rotation speed and phase current.According to the existing principle of numerical analysis of permanent magnet(PM)eddy current loss,the change tendency of PM eddy current loss with the change of motor control parameters is illustrated.Subsequently,combined with the field-coupled analysis method,the two-dime nsional finite element analysis(2D FEA)model of PMSM is established to anlyze the electromagnetic field in the special operating condition and the magnetic density of the magnetic field in the PM.The spatial distribution of the eddy current density and eddy current loss in the permanent magnet is obtained through the previous anlysis.The variation regularity of direct-axis current and PM eddy loss is studied,which is not involved in analytical method.Finally,according to the variation law of the PM eddy current loss under the different motor control parameters determined jointly by the analytical method and the FEA method,calculation formula of PM eddy current loss over the entire torque-speed envelope in PMSM for electric vehicles,which could take temperature factor account,is established.The results of fast calculation method are verified by 3D FEA。...