Research On Electromagnetic Noise Of Integrated Electric Drive Axle

The integrated electric drive axle is the core component of electric vehicles.In order to meet the performance requirements of the drive motor for high power,high speed and heavy load,and efficient cooling,the electromagnetic vibration and noise performance of the electric drive axle is deteriorated.The electromagnetic noise of the electric drive axle plays an important role in the overall NVH performance of the vehicle,so it is necessary to strictly control its electromagnetic noise.A new integrated electric drive axle was found to have an unacceptable electromagnetic noise problem during the prototype verification.This article analyzes its mechanism and influencing factors,and proposes an improvement plan.First,through the prototype vibration and noise bench test,the electromagnetic noise problem of the integrated electric drive axle is evaluated and analyzed in detail.The results showed that: The main electromagnetic noise sound pressure level produced by the induction motor in the speed range of 0～2400r/min is far greater than twice the main noise sound pressure level produced by gear meshing;The sound pressure level curve first increases and then decreases with the rotation speed,and the peak value of electromagnetic noise reaches 77.36 d B,which is far beyond the range of the sound pressure level limit curve;The main vibration and noise orders that cause this noise problem are 57.6 orders and 61.6 orders.Then,in order to explore the electromagnetic noise of the prototype,it is necessary to establish the electromagnetic vibration excitation source,namely,the analytical model of the radial electromagnetic force wave and the electromagnetic vibration and noise simulation model.At the same time,in order to accurately build the electromagnetic vibration and noise simulation model,the effectiveness of the two-dimensional electromagnetic finite element model,the three-dimensional structural finite element model and the acoustic boundary element model was verified by the analytical model and the induction motor output characteristic test,free mode test,and vibration and noise test.Secondly,based on the established model,the causes and influencing factors of the electromagnetic noise of the electric drive axle are analyzed.Through the Donnell shell theory,the space-time characteristics of radial electromagnetic force waves and the modal shape of the structure,and the multi-physics vibration and noise simulation model to explore the effects of different space-time characteristics of radial electromagnetic force waves,mode matching and structural damping on electromagnetic noise law.The analysis shows that the electromagnetic vibration in the electric drive bridge is approximately inversely proportional to the fourth power of the force wave order,and low-order force waves have higher noise radiation efficiency in low frequency bands;In an induction motor with a wide speed range,it is difficult to avoid electromagnetic resonance due to the matching of the force wave order and the shape of the stator core,which is also the main cause of the electromagnetic noise problem of the electric drive bridge;Both electromagnetic vibration and noise decrease with increasing damping ratio.Finally,in view of the electromagnetic noise problem of the prototype,this paper improves the prototype by opening auxiliary slots in the rotor of the induction motor and selecting the best slot matching to reduce the amplitude of the radial electromagnetic force wave and change the force wave vibration shape.The electromagnetic noise of the improved electric drive bridge is calculated based on the multi-physics vibration and noise simulation model.The results show that: By selecting the 60/74 slot fit,the average torque and efficiency drop of the induction motor under steady-state conditions can be kept within 5%,and the solution can stabilize the occurrence of electromagnetic resonance.Under working conditions,the 1m sound pressure level of the electric drive axle is reduced by 9.8d B,and the effective value of the electromagnetic noise 1m sound pressure level within the speed range of 6000r/min is reduced by 4.98 d B,so that the overall sound pressure level curve is kept within the noise limit curve range to meet the low requirements.The demand for electromagnetic noise.