Research On Electromagnetic Compatibility Analysis And Improvement Of Passenger Car Cooling System

Today,the vehicle system is constantly moving towards electromagnetism,intelligent,integrated direction,a large number of electrical systems integrates in the small space of the car to form a relatively complex electromagnetic environment.The electrical system works serious electromagnetic interference to other electromagnetic sensitive components,affecting the normal operation of the system.In the traditional automotive industry,the electromagnetic compatibility performance of the product is often gradually improved by repeated experiments.Since the product has been put into prototype,the problem is found to be solved,the measures are limited and the cost is high.To resolve the electromagnetic compatibility problem in the vehicle,the product is effective in electromagnetic compatibility analysis in the early stage of the vehicle design,from subtraction transformation into the concentration.Under the support of the company’s project,the optimization measures for electromagnetic interference of cooling fan motor were studied,and the purpose was to optimize the electromagnetic compatibility of the car cooling system after the in-depth study of the cooling fan motor.The main contents of this paper are as follows:(1)The structural and working principle of a small permanent magnet DC motor in the automobile cooling system is analyzed.Analysis from the principles and structural levels,the cause of electromagnetic interference of cooling system is explored,and the electromagnetic compatibility of cooling system has an important impact on electromagnetic compatibility of the vehicle.When analyzing the electromagnetic compatibility performance of the cooling system,the electromagnetic compatibility performance of the cooling fan motor is analyzed.(2)On the basis of sufficiently understanding the principle of cooling fan motor,electromagnetic interference simulation prediction is performed on the cooling fan motor model.Creating a cooling fan motor radiation interference finite element model: The end voltage of the actually measured cooling fan motor is an excitation source,and the radiation electric field is obtained.The accuracy of the model is verified by comparison with the measured data by simulation data.(3)The method and principles of four EMC rectification were analyzed for the actual situation of the cooling fan motor,namely,the absorbing,filtering,shielding,and grounding,and simultaneously performing circuit design and utilizing models to estimate EMC performance.In the end,the cooling fan motor is improved in the support of the relevant theory and the model verification.(4)For the circuit design,in order to reduce the current throughput of common mode current,the design and installation of bypass capacitors are selected to control the current throughput.Through actual measurement,it is found that the current passing through the device in advance can effectively weaken the electromagnetic conduction and radiation,and the weakened electromagnetic radiation can return normally.(5)Perform actual sample production and test test test.Through the test verification method,the low-voltage DC motor EMC characteristics,including impedance characteristics,conductive emission characteristics,radiation emission characteristics,transient conduction emission characteristics,etc.,explore different test factors for test results.For electromagnetic compatible test items,test methods,test procedures,venue layouts,and results to speculate in order to accurately standardize electromagnetic compatible measured data.In response to the control group set by the prototype,the measured results are drawn into a form to find the best measures.Finally,by theoretical analysis and experimental verification,it is understood that the metal graphite carbon brush can be selected for a carbon brush,which can suppress the reverse spark condition to a certain extent.For motor levels,by absorbing,filtering,shielding,and grounding four measures can be greatly suppressed to improve electromagnetic compatibility performance without affecting the normal operation of the cooling system.