| In recent years,the development of new energy vehicles has been very rapid,and the emerging forces of Internet-made vehicles have sprung up in front of the public.At the same time,with the development of motor technology at home and abroad,especially the improvement of the performance of permanent magnet materials such as NdFeB,permanent magnet synchronous motor has gradually become a research hotspot in universities and automotive enterprises.The power density,heat loss and efficiency of the motor have been greatly improved.However,whether it is the transformation of traditional automobile enterprises into new energy vehicles or new forces,they are paying attention to the noise problems of motors while paying attention to the dynamic performance and endurance of automobiles.The noise of the motor is related to the NVH characteristics of the vehicle,which will seriously affect the ride comfort of the car occupants.Nowadays,the mainstream development direction of motor noise optimization includes four aspects: electromagnetic parameter optimization,current control optimization,rotor oblique pole chute and motor body structure modal optimization.In order to more accurately explore the vibration and noise of the motor,accurate analysis of the magnetic field of the motor is required.Based on the harmonic modeling method,a two-dimensional magnetic field analytical model of an external rotor-wheel permanent magnet synchronous motor is established.The model is used to calculate the electromagnetic performance of the motor under no-load,armature field and load conditions when the relative magnetic permeability of the stator is 5000.The curves of air gap flux density,back MF,cogging torque and output torque are obtained.The finite element simulation and experimental tests show that the model is very accurate.Compared with the traditional sub-domain analytical model method,the analytical model breaks the barrier that can not consider the magnetic permeability of the stator and rotor,making the analytical model more accurate and realistic.For the outer rotor permanent magnet motor casing,the modal frequency and vibration mode of the motor casing are calculated by using finite element software.The free modal test is used to verify that the finite element model can be used for vibration noise analysis.In order to investigate the electromagnetic force characteristics of the motor,the electromagnetic force distribution of the motor in space,time domain and frequency domain is calculated based on the analytical method,and verified by finite element software.Based on the rotor casing model,the forced vibration deformation results of the motor casing are obtained by the finite element harmonic response module analysis.Using this result,the distribution of sound pressure and sound pressure level of the motor casing is obtained in the finite element software noise calculation module.The research shows that the peak sound pressure level is mainly distributed around 750 Hz and 1900 Hz under the rated operating conditions of the motor,and the total sound pressure level is 86 dB.Based on the analytical model,the influences of four factors,such as magnetic permeability material,polar arc coefficient,slot opening width and auxiliary slot,on the magnetic field of the motor are studied.Combined with the finite element simulation software,the four are studied.The influence of influencing factors on motor vibration and noise.The research shows that as the relative magnetic permeability of the magnetically permeable material increases,the total sound pressure level of the motor noise becomes smaller;as the polar arc coefficient increases,the total sound pressure level decreases first and then increases;Gradually increasing,the total sound pressure level gradually increases;after the auxiliary tank is increased,the total sound pressure level becomes smaller.Combined with four factors,the motor is comprehensively improved and optimized.The total sound pressure level of the motor noise is reduced from the original 86.72 dB to the optimized 77.96 dB,and a good noise reduction effect is obtained. |
