Research On Electromagnetic Field Analysis And Diagnosis Method Of The Interior Permanent Magnet Synchronous Motor With Eccentricity Fault

The interior permanent magnet synchronous motor(IPMSM)has become one of the main driving motor type of electric vehicles due to the advantages of strong anti-demagnetization ability,good weak magnetic speed expansion capability and high torque power density.However,due to the motor manufacturing errors and installation errors and bearing wear and so on,the IPMSM may have eccentricity fault,which will cause the air gap magnetic field to be distorted,resulting in unbalanced magnetic force,which will cause vibration and noise of electric vehicle.Even,the stator and rotor will contact,causing the motor to wear and even burn.Therefore,research on electromagnetic field analysis and diagnosis method of the interior permanent magnet synchronous motor with eccentricity fault has important theoretical significance and engineering value.The main research work and achievements of this paper are as follows:(1)Analytical modeling analysis of the air gap magnetic field and electromagnetic force modeling and characteristic analysis of the IPMSM without eccentricity.Firstly,the semi-analytical model of the air gap magnetic field of the IPMSM was established by the superposition method and complex relative permeability and permeability correction factor of flux barriers,considering complex structural factors such as segmented oblique poles,multi-layer flat wire windings,and magnetic isolation bridges.The time and space characteristics were analyzed.Secondly,using the Maxwell tensor method,an electromagnetic force analytical model was established,the space-time characteristics of electromagnetic force were revealed.Then,the correctness of the analytical calculation is verified by the finite element model.The research shows that stator slotting will cause the magnetic field to have ±?Qs effect on the original spatial order components;the magnetic bridge will have ±2mp effect on the spatial order and ±2mfc effect on the frequency component of the magnetic field,m?0,1,2,3…….(2)Analytical modeling analysis of the analytical model and electromagnetic force analytical model of the air gap magnetic field of the IPMSM with static eccentricity.Firstly,the analytical model of the air gap magnetic field of the IPMSM with static eccentricity was established by magnetic permeability correction coefficient method,considering static eccentricity fault.The spatial order and frequency characteristics of the air gap magnetic field of the IPMSM with static eccentricity were analyzed.Next,the analytical model of the electromagnetic force of the IPMSM with static eccentricity was established by maxwell stress tensor method.The spatial order and frequency characteristics of the electromagnetic force were analyzed.The influence of different static eccentricity ratio and different static eccentricity positions on the unbalanced force were studied.Then,the correctness of the analytical calculation is verified by the finite element model.The results show that,there are ±1 order component on the basis of the original space order of air gap field when motor exsits static eccentricity.And there are ±1,±2 order component on the basis of the original space order of electromagnetic force wave when motor exsits static eccentricity.There is no influence on the frequency characteristics of the unbalanced magnetic force when motor exsits static eccentricity.But with the increase of static eccentricity ratio,with 0Hz harmonics of unbalanced magnetic force as the main component,the 2Nfc harmonics of unbalanced magnetic force increase gradually,N?0,1,2,3…….(3)Analytical modeling analysis of the analytical model and electromagnetic force analytical model of the air gap magnetic field of the IPMSM with dynamic eccentricity.Firstly,the analytical model of the air gap magnetic field of the IPMSM with dynamic eccentricity was established by magnetic permeability correction coefficient method,considering dynamic eccentricity fault.The spatial order and frequency characteristics of the air gap magnetic field of the IPMSM with dynamic eccentricity were analyzed.Next,the analytical model of the electromagnetic force of the IPMSM with dynamic eccentricity was established by maxwell stress tensor method.The spatial order and frequency characteristics of the electromagnetic force under dynamic eccentricity were analyzed.The influence of different dynamic eccentricity ratio on the unbalanced force were studied.Then,the correctness of the analytical calculation is verified by the finite element model.The results show that,the influence of dynamic eccentricity on the spatial order of air gap magnetic field and electromagnetic force wave were the same with static eccentricity.But there are ±fr frequence characteristics on the basis of the frequence characteristics of air gap field when motor exsits dynamic eccentricity.And there are ±fr,±2fr frequence characteristics on the basis of the original frequence characteristics of electromagnetic force wave when motor exsits dynamic eccentricity.With the increase of the dynamic eccentricity ratio,the fr harmonics of unbalanced magnetic force increase significantly and the 4fc±fr,6fc±fr,8fc±fr harmonics of unbalanced magnetic force also increase.The direction of the unbalanced magnetic force changes continuously with the rotation of the rotor when there is dynamic eccentricity.(4)The eccentricity fault diagnosis method of IPMSM was studied.The analytical model of three phase no-load back electrical magnetic force of the IPMSM was established by faraday law of electromagnetic induction,considering the influence of the number of segmented oblique poles and the number of winding parallel branches.The influence of the number of segmented oblique poles and the number of winding parallel branches on the three-phase no-load back EMF of the motor were studied.The influence law of static and dynamic eccentricity on the three-phase no-load back EMF of unit motor were explored.On this basis,the BP neural network model is established.Based on the no-load back EMF of the element motor,the static eccentricity fault and dynamic eccentricity fault diagnosis method of the IPMSM are proposed.The results show that,the static eccentricity fault causes the average total harmonic distortion of the three-phase no-load back EMF of each unit motor to change accordingly.The dynamic eccentricity fault causes the average concavity of the three-phase no-load back EMF of the unit motor to change accordingly.However,the series-parallel connection between the windings will offset the influence of the eccentricity fault on the three-phase no-load back EMF of the motor.