| Modern automobiles work in an increasingly harsh electrom agnetic environment.Due to the requirements of automotive safety,the bulk current injection immunity test based on the substitution method is applied to the electromagnetic compatibility test of automotive components.This paper uses the bulk current injection method to test the immunity of an automobile component in common-mode interference and differential-mode interference mode respectively.Usually,shielding method is used to solve EMC problem.In this paper,CST simulation software is used to study the influence of conductive adhesives size and conductivity on shielding effectiveness.The experimental characteristics of the device under test in the two interference modes and different working modes are compared and analyzed.The test setup is in compliance with the ISO 11452-4 standard and the applicable frequency range of the bulk current injection test method is 1MHz to 400 MHz.The results show that in the low frequency band(1MHz-30MHz)the current coupled into the harness under the common mode condition is larger than that in the differential mode,and the resonance phenomenon occurs in the high frequency band.In the high frequency band,there is a phenomenon that the current coupled into the wiring harness under the common mode condition is less than the current that is coupled into the wiring harness under the differential mode due to the resonance phenomenon.In the immunity test using bulk current injection method,only the common-mode method is included in ISO 11452-4 test standard.Therefore,this paper puts forward that,when the bulk current injection method is used to the immunity test of the device under test,the differential-mode interference should be considered in the immunity test.Using CST simulation software establish the simulation model of shielding effectiveness of conductive adhesives.The results show that the bigger the conductivity and thickness of conductive adhesives is,the greater the corresponding shielding effectiveness is.When the thickness of conductive adhesives is 1mm,the shielding efficiency of conductive adhesives with conduct ivity of 2S/m increases by 2.5dB compared with conductive adhesives with conductivity of 0.2S/m.Compared with conductive adhesives with conductivity of 2S/m,the shielding effectiveness of conductive adhesives with conductivity of 20S/m increases by 12 dB.Compared with conductive adhesives with conductivity of 20S/m,the shielding effectiveness of conductive adhesives with conductivity of 200S/m increase s by 20 dB at least.When the thickness of conductive adhesives is 2mm,the shielding efficiency of conductive adhesives with conductivity of 2S/m increases by 4dB compared with that of conductive adhesives with conductivity of 0.2S/m.Compared with conductive adhesives with conductivity of 2S/m,the shielding effectiveness of conductive adhesives with conductivity of 20S/m increases by 11 dB.Compared with conductive adhesives with conductivity of 20S/m,the shielding effectiveness of conductive adhesives with conductivity of 200S/m increases by 25 dB at least.When the conductivity of conductive adhesives is 200S/m,the shielding efficiency of conductive adhesives with thickness of 2mm is increased by 22 dB compared with that of conductive adhesives with thickness of 1mm.Compared with conductive adhesive with thickness of 2mm,the shielding effectiveness of conductive adhesive with thickness of 3mm increased by about 25 dB. |
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