Influence Of Uncertain Contact Area Parameters Of Parts On Electromagnetic Vibration Of Alternator

As a major sources of noise pollution,automobile noise has received more and more attention.Alternator electromagnetic noise is an important part of automobile noise.When alternator is mass-produced,there is a problem that the peak value of the same type of alternator's electromagnetic noise corresponds to the inconsistent rotational speed.The uncertainty of contact areas between various parts of alternator can cause its modal frequencies inconsistency,which causes the peak value of the electromagnetic noise of alternator corresponds to the inconsistent rotational speed.Therefore,it is necessary to study the electromagnetic vibration characteristics of alternator with uncertain contact area.In this paper,based on the problem that the peak value of the electromagnetic noise of the same type of alternator is inconsistent with the speed,the modal and electromagnetic vibration of the alternator with uncertain contact area are studied used the Kriging surrogate model and Monte Carlo method.In the first,modal characteristics of parts and the whole machine of the actual alternator were tested by modal experiments.The finite element model of parts and the whole machine of the actual alternator were built.The modal frequencies of the alternator parts and the whole machine is calculated by the established model,the correctness of the finite element model is verified by comparison with the experimental test results.The samples collection methods and prediction model construction methods were compared.Orthogonal test design method and Kriging function method were used to establish the surrogate model.Based on the established finite element model and the orthogonal experimental design method,32 finite element model samples are collected,and 32 samples take the different combinations of the contact area parameters of the 9 parts into account.The Kriging surrogate model was verified by the results of the complex correlation coefficients and the first-order elliptic modal frequencies of surrogate model.Based on the Monte Carlo method and the Kriging surrogate model for the modal calculation of the alternator with uncertain parts' contact areas,the modal frequencies of the alternator with uncertain parts' contact areas were simulated and calculated.According to the simulation results,the modal frequency deviations of the alternator with uncertain parts' contact areas were analyzed.The sensitivity of the frequency deviations for the alternator to the parts' contact area were studied.The results show that the contact areas between stator core and the front end cover have the greatest influence on the modal frequencies of the first and second order elliptic and the fourth order triangular modal frequencies.The greatest influence on the third-order triangular modal frequencies are the contact areas between the claw pole and the coil,and the contact areas between stator core and the winding have a great influence on the first-order elliptic modal frequencies,the third-order and fourth-order triangular modal frequencies.Based on the finite element method of electromagnetic force calculation,a finite element model of the electromagnetic force calculation of alternator was built,and the 3-way electromagnetic force on the stator teeth of alternator were calculated.The radial vibration accelerations of the measuring points on alternator's outer end cap were tested,the finite element model of the electromagnetic vibration response of the alternator was built.The correctness of this model was verified.Based on the finite element model of alternator's electromagnetic vibration response,the changes in vabriation response in different working conditions(2400 rpm,3000 rpm and 3600 rpm)of the alternator were studied when the stator core and the front end cover were 1/3 contacted,the front and rear end cover bolts' junction surface were 1/2 contacted,and the claw pole and the shaft were1/2 contacted.The results of the study show that when the contact areas of some parts changes,the frequency and amplitude of the "formant" of the alternator's electromagnetic vibration response changes correspondingly,which verified the conclusion of the reseach on the influnence of the components with uncertain cantact areas on frequency of alternator modal.The sizes of the stator core and the fitting between stator core and the front end cover,the amount of impregnation of the stator core,the size of the claw poles,and the fitting between the claw poles with the rotor coils have an effect on improving of the modal frequency deviations of alternator.When there is a inconsistency in the frequencies of the modal,the dimensions of the claw pole and its coordination with the coil and the change in the amount of impregnation of the stator windings have a great effect to improve the frequencies inconsistency of the first-order elliptic and the third-order triangular modal;improving the dimensions of the claw pole,the shaft and their matching relationship is more effective in reducing the frequency inconsistency of the second-order elliptic modal;the optimization of the size and the matching relationship between the stator core and the front cover can effectively reduce the frequency deviations of forth-order triangular modal.The research results of this paper can solve the problem of the inconsistent speed of the alternator's electromagnetic noise peak corresponding to the speed,and provide guidance for the production and processing technology to improve the poor modal consistency of the same type alternator.