Analysis And Suppression Of Vibration Noise Of Traction Lowspeed Permanent Magnet Synchronous Motor

The major sources of noise in the operation of permanent magnet motors consist of three aspects: one is the electromagnetic noise produced by the interaction of harmonics between the air gaps;the other is the mechanical noise induced by the mutual friction between bearings or stators and rotors,etc.The third source of noise is the aerodynamic noise provided by the fan’s spin or the resonance created in the gap.Mechanical and aerodynamic noise can be reduced by enhancing the motor’s manufacturing quality and improving the process flow.However,the study discovered that suppressing these two types of noise is ineffective in reducing the overall vibration noise of the motor,as a result,the motor’s electromagnetic noise is the primary source of the motor noise.This research focuses on the electromagnetic noise generation process of motor and the vibration noise mitigation strategies.The space-time characteristics of the permanent magnet motor’s radial electromagnetic force are investigated,the natural frequency of the permanent magnet motor casing is calculated,the impact of motor structure parameters on motor performance and vibration noise is investigated,and the motor structure is improved and parameters optimized.The following is a list of the research’s detailed contents:（1）The electromagnetic system design of the traction permanent magnet synchronous motor is completed based on the design parameters and technical requirements,and the major dimensions of the motor as well as critical parameters such as the rotor structure are decided.At the same time,the magnetic induction intensity,magnetic field line distribution,air-gap flux density,and motor performance are investigated under no-load and load situations to see if the performance characteristics fulfill the design criteria.（2）The electromagnetic noise of a traction permanent magnet synchronous motor is investigated,with a focus on the radial electromagnetic force’s spatial order and timefrequency laws.To confirm that the analytical calculation is correct,finite element software is used to model the spatial and temporal distribution of radial electromagnetic force under no load and under load,as well as the frequency domain properties of electromagnetic force.（3）To determine the natural frequency,vibration response,and total noise sound pressure level of the outer rotor permanent magnet motor casing,create a finite element model and evaluate the modal frequency and mode shape of the motor casing using Workbench.The harmonic response module in Workbench was used to obtain the forced vibration deformation results of the motor shell based on the rotor shell model.The sound pressure and sound pressure level distribution of the motor casing are calculated using this result in conjunction with the finite element noise module.（4）Starting with improving the motor’s structural parameters,motor models with various different air gap lengths,pole arc coefficients,and stator slot opening widths were created to investigate the impact of the above structural parameters on motor torque performance and vibration noise.Simulation is used to obtain the radial electromagnetic force,vibration response,and noise sound pressure level waveforms of the motor under various parameters,and the changing laws of the above waveforms are compared and analyzed,as well as the influence laws of the above three factors on the overall performance of the motor.Finally,the motor is improved and optimized in light of the previous structural parameters.