| The driving motor is a key component of the electric vehicle,and its performance directly affects the subjective feeling of the occupant.The vehicle-driven permanent magnet synchronous motor is widely used in electric vehicles due to its high power density,wide speed range and fast response.At the same time,these advantages also lead to the compact and complex motor structure which is easy to be excited.The wide speed range makes the resonance risk much greater than other types of motors.Therefore,how to analyze and suppress the vibration and noise of the drive motor becomes a key issue to improve the performance of the electric vehicle NVH.First,the theoretical analysis of the electromagnetic field of the motor is carried out,and the expressions of the air gap magnetic field and the air gap force wave are derived.The three-dimensional finite element model of electromagnetic field is established by Maxwell software,and the magnetic field distribution and magnetic dense cloud diagram of the motor are obtained.Post-processing calculates the air gap magnetic density frequency distribution and amplitude.The electromagnetic field theory is used to calculate the air gap force wave.The spectrum characteristics of the air gap are consistent with the theoretical analysis by FFT.Then,based on the virtual displacement method,the force of the stator tooth when the motor is running at a steady speed is calculated.The transient electromagnetic field model is used to calculate the loss of each part of the motor.Because the permanent magnet eddy current loss and the rotor core loss account for a small proportion,only the stator core loss and the winding copper loss are considered.The magnetothermal coupling method is used to load the loss into the three-dimensional temperature field model to calculate the motor temperature distribution.Simulation modal analysis and modal experiments were performed on the motor stator system.The modal extraction algorithm for orthotropic structures is compared and analyzed.The results show that the Lanczos method has the highest efficiency.The free-mode simulation analysis is carried out by establishing the isotropic structure of the stator system and the orthotropic stator system considering the lamination effect.The modal experiment was carried out by the moving sensor method and compared with the simulation results.The results show that the stator system with orthotropic structure is closer to the experimental result than the isotropic structure.A magnetic-solid-thermal coupling analysis model was established,and a good electromagnetic field and temperature field model was established using Workbench for coupling analysis.The electromagnetic force and temperature are loaded into the structural field model to calculate the deformation of the stator,and the feedback is recalculated to the electromagnetic field.After the feedback is stabilized,the air gap magnetic density distribution trend is basically the same as the initial electromagnetic field,but the amplitude is slightly smaller.The electromagnetic force of the stator tooth after considering the temperature and structural deformation is calculated by the model.The electromagnetic vibration response and acoustic radiation of the motor are calculated by the modal superposition method and the ATV response.The results of the comparison before and after the feedback show that the temperature has little effect on the electromagnetic vibration.According to the corresponding national standard of the motor noise experiment,the vibration noise experiment was carried out in the semi-anechoic chamber,and the motor noise characteristics were analyzed by designing the lifting speed and the steady speed working condition.Comparing the simulation results with the experimental results,the calculated trend of the sound pressure level curve basically corresponds to the experimental results,but the amplitude is smaller than the experimental results due to different excitation conditions and boundary conditions.In general,the model can be used to predict the vibration noise of permanent magnet synchronous motors. |
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