Study On Characteristics And Influencing Factors Of Electromagnetic Virbration And Noise Of Automotive Alternator

The noise of alternators is the hot spot in vehicle NVH research field. The domestic alternators’ NVH performance could have reached,even more than the level of the developed countries’s similar products by taking appropriate measures and controlling the production process strictly basing on the research of electromagnetic noise of vehicle alternators.But the problem that the electromagnetic noise amplitude and resonance speed (frequency) is inconsistent always exists in mass production.In this paper,the characteristics and influencing factors of the alternator’s vibration and noise will be studied through the experiment and simulation by taking typical alternators as the object.The vibration and noise experiments are taken respectively in no load, load in cold state and load in hot state to found that the 36th order noise determines the level of the overall noise and the noise in cold state is generally bigger than the noise in hot state. By comparing the sound pressure level curves of the different alternators in the same type and different states of the same alternator.it is founded that amplitude of noise peak and resonance speed is inconsistent. by frequency spectrum analysis,it is obtained that the noise and vibration have the same frequency components, indicating the noise is caused by vibration, and the scope of resonance frequency.of the alternators.Modal characteristics of parts and the whole machine is obtained by modal experiments. By analyzing the individual frequency fluctuations between the parts,it is found that the consistency of the elliptical modal is better than triangular modal and the consistency of the individual part is better than the assembly’s.Establishing the finite element model of parts and the whole machine, it is obtained that the error between simulation results and the experiment results is around 5.0% through the modal analysis in ANSYS Workbench software, meanwhile the accuracy of the finite element model is verified. It is obtained that the front cover influences the elliptical modal mostly and the stator winding influences triangular modal mostly by changing the elastic modulus of every part.After that it is concluded that the contact is the main influence factor of the whole machine’s modal by changing the contact between parts. In practice, the different process errors and working conditions lead to different modals among alternators by causing different contact between parts in alternators.Put forward the relation between the vibration displacement of the stator’ measuring point and the stator teeth harmonic force and the modal characteristics.Through the theoretical analysis,the vibration displacement should be zero when the distribution of the electromagnetic force is even,and the vibration displacement should be larger than the former when the distribution of electromagnetic force is uneven.On the basis of the research results of the electromagnetic wave, the electromagnetic force under different air gap is loaded on the stator teeth to make harmonic response analysis of the stator and the whole alternator respectively by ANSYS Workbench. The theoretical analysis of vibration displacement synthetic formula is verified through the calculation results.The simulation calculation shows that the vibration response increases respectively as the air-gap eccentricity and the stator thermal expansion increases, vibration response of the whole alternator is larger than the vibration response of a single stator when the air gap is uneven.In this paper,the characteristics and influence factors of the electromagnetic vibration noise is studied by combining experiment and simulation calculation.The conclusion that the influence factors of the modal and the influence law of air gap to electromagnetic vibration has reference value to the engineering practice and guide for controlling measures of process...