Analysis Of Electromagnetic Vibration And Noise In Permanent Magnet Brushless DC Motors

With the development of high-end motor industry,the demand for low energy consumption and high performance motors is increasing day by day.With its low starting torque,low loss and flexible control,the permanent magnet brushless DC motor is widely used in electric vehicles,household appliances and small motors,and the ensuing noise problem has become a growing concern.The vibration and noise problems of motors can lead to motor fatigue,shorten the life of the motor,and affect the life and study of users,so the exploration of vibration and noise of permanent magnet brushless DC motors has certain research value.In this paper,the electromagnetic field,structural dynamics and acoustics are combined to analyze the electromagnetic field distribution,structural modalities and vibration noise of permanent magnet brushless DC motors.Firstly,the source of electromagnetic force wave is explored by the analytical method,and the magnetic field distribution of the motor is calculated by finite element simulation to obtain the main order force wave that causes motor vibration.For the motor structure in this paper,the structural parameters of the motor are optimized with the lowest harmonic distortion rate and the maximum motor load efficiency as the target,and the pole arc coefficient and pole eccentricity distance as the variables.By parametric scanning of the magnetic density,the best combination of parameters with the lowest harmonic distortion rate of the radial component of the magnetic field and the most significant weakening of the tangential component amplitude is obtained while ensuring the efficiency of the motor.The modal analysis of the motor is then carried out,and the modal vibration pattern of the stator core and the corresponding modal frequency are simulated and calculated by the finite element method,and the influence of the housing and end cover on the modal vibration pattern of the stator core is discussed,and the inherent frequencies of different motor models are obtained,and compared with the electromagnetic force oscillation frequency to determine whether it will cause the motor resonance.Then the Maxwell electromagnetic module is connected to the structural dynamics module in Workbench,and the electromagnetic force is introduced into the inner side of the motor stator uniformly in segments as the excitation source to simulate the vibration response of the motor under the action of electromagnetic excitation force;then the acoustic module is connected to the structural dynamics module,and the acoustic boundary element method is combined with the vibration speed as the load to observe the sound pressure cloud of the motor under the vibration excitation The acoustic module is then connected to the structural dynamics module,and the acoustic boundary element method is combined with the vibration speed as the load to observe the acoustic pressure cloud and the variation of radiated noise with frequency under the vibration excitation.Finally,the vibration data and radiated noise decibel values of the motor before and after adopting the optimal structural parameters are compared and analyzed to verify the effectiveness of the optimization scheme,which provides a reference basis for the subsequent in-depth investigation of the vibration and noise of permanent magnet brushless DC motor and the optimization scheme of noise reduction.