Research On Demagnetization Fault Of Surface-mount Permanent Magnet Synchronous Motor

Due to its unique permanent magnet structure,permanent magnet motors have an irreversible risk of demagnetization in the operation of the motor compared to induction motors.Therefore,in order to ensure the safe and reliable operation of the permanent magnet synchronous motor,the multi-feature variation of the internal electromagnetic field of the motor demagnetization fault is deeply studied.The analysis and extraction of the reliable fault feature quantity has become one of the key issues to solve the demagnetization fault diagnosis of the permanent magnet synchronous motor.In this paper,the demagnetization fault of surface-mount permanent magnet synchronous motor is taken as the research direction,and the changes of key performance parameters such as electromagnetic field,electromagnetic force,electromagnetic torque,electromagnetic vibration of stator core surface and the coupling effect of internal multiphysics are analyzed in depth.Through in-depth study of the operating state of the permanent magnet motor and the change of electromagnetic parameters under the demagnetization fault,the multiple feature quantities closely related to the demagnetization fault are analyzed and extracted,and the variation law of the feature quantity is summarized to diagnose the demagnetization fault of the permanent magnet synchronous motor.It provides theoretical support for demagnetization online monitoring that realizes multi-feature signal fusion,and is of great significance for realizing the safe and reliable operation of permanent magnet synchronous motor.The main research contents of the thesis are as follows:(1)The finite element model of demagnetization fault of permanent magnet synchronous motor is established.The time-step finite element method is used to analyze the air gap magnetic field,armature current,back electromotive force waveform,flux linkage waveform and magnetic field trajectory under different degrees of demagnetization.And the variation law of the magnetic density characteristics of the stator core.Based on the Fourier series harmonic decomposition theory,the air gap magnetic field,induced potential and current harmonic content change under different degrees of demagnetization are compared and analyzed.Finally,according to thecorresponding change characteristics of the above electromagnetic parameters,the demagnetization fault state of permanent magnet synchronous motor is analyzed.A comprehensive analysis of several characteristic quantities of the lower electromagnetic field was carried out.(2)Using mathematical derivation to theoretically analyze the magnetomotive force,electromagnetic force density and electromagnetic torque of permanent magnet synchronous motor,study electromagnetic force density and electromagnetic torque and air gap magnetic density radial,tangential component and other electromagnetic The intrinsic connection of the parameters,and the spatial distribution and time distribution characteristics of the electromagnetic force density under different operating conditions of the motor and the electromagnetic resultant force of the inner surface of the stator core at different moments are analyzed.The magnetic field demagnetization fault of the permanent magnet synchronous motor is studied later.The basic law of the change of electromagnetic force is used as a basis for comparative analysis.(3)The variation of electromagnetic force parameters and electromagnetic torque of permanent magnets in permanent magnet synchronous motor and the demagnetization of all permanent magnets are analyzed.The electromagnetic force spatial distribution and time distribution harmonics of the inner surface of the stator under motor demagnetization fault are analyzed comprehensively.The frequency domain characteristics of the electromagnetic force combined with the inner surface of the stator core are summarized,and the electromagnetic force parameters and electromagnetic torque characteristic data sets are summarized.The electromagnetic force parameters and electromagnetic torque are revealed as the intrinsic feature quantity of the motor with different degrees of demagnetization of the permanent magnet.The law of change.(4)Combining the previous analysis and research,the electromagnetic-structure coupling analysis method is used to further study the electromagnetic vibration of the stator core surface under permanent magnet synchronous motor demagnetization fault.Firstly,the harmonic response analysis is used to obtain the motor rated load in all directions.Vibration displacement,secondly,the vibration displacement of the stator core surface along the x,y,and z axes in the demagnetization of the permanent magnetand the uniform demagnetization of all permanent magnets.Finally,the direction of the stator core surface of the motor under the demagnetization fault state The vibration displacement variation law was comprehensively analyzed.