Research On Electromagnetic Effect Of Complex Vehicle Cables

With the improvement of automotive electrical degree, the maneuverability and safetyof modern vehicles are reliant on electronic control systems more seriously. At the sametime, higher requirements are put forward for vehicle electromagnetic compatibletechnology in the increasingly complex electromagnetic environment. Especially in theenvironment of HEMP (high altitude electromagnetic pulse), electronic equipment insidethe vehicle will be seriously disturbed and even damaged. Electromagnetic compatibilitybecomes one of the most important signs which guarantees the safety and maneuverabilityof vehicles. The cables are the key to connect the electronic equipment in the vehicle, butthey are also the most important coupling channels which make electromagnetic energycouple into electronic control systems. The cables have complex structures, irregular shape,large quantity, high density and can be found everywhere in the vehicle. But the size ofcables is so small compared with the size of the vehicle shell, so it is hard to obtain theresults of cables’ electromagnetic effects with high precision in neither theory analysis norsimulation analysis. Deeply researching the mechanism and effect of complex vehiclecables’ electromagnetic coupling has great significance to the design and engineeringimplement of vehicle electromagnetic compatibility.In this paper, the electromagnetic topology is applied to solve the problem ofelectromagnetic effect of vehicle cables. The electromagnetic topology structure of cables isanalyzed and divided. Then the coupling mechanism of external electromagnetic field to thecables in the vehicle is studied layer by layer. The vehicle cables are described into fivetypical models which are single wire, double wire, multi-core wire, wire network andshielded wire. By combining the CST simulation of the electric field inside the car,BLT transmission line equation and the field-to-line coupling model, electromagnetic effectof five cable models are calculated with HEMP excitation outside the vehicle, and shieldedcable grounding is preliminarily studied inside the car. A large amount of simulation data areobtained, which provide theoretical basis and engineering guidance for electromagneticprotection of vehicle cables.The main contents and contributions of this paper are as follows:(1) Electromagnetic topology theory is applied to analyze the complex vehicle cables.The vehicle is divided into two levels: cables and vehicle shell, and their electromagnetictopological models are established. The coupling mechanism of external electromagneticfield to the cables is analyzed layer by layer. Comparative analysis of three classical field-to-line coupling models are made which are Taylor model, Agrawal model,Rachidi model. According to the actual situation of the vehicle cables, Agrawal model isselected to calculate their electromagnetic effect.(2) Time domain and frequency domain characteristics of HEMP excitation areanalyzed. BLT transmission line equation and the field-to-line coupling model are used tostudy the electromagnetic effect of single wire and double wire on the ground with theHEMP excitation. Then the results are compared with the CST simulation to verify thealgorithm. In the environment of HEMP, the electromagnetic response of the simple cablemodel in the vehicle is studied by combining the algorithm above with the CST simulationof the electric field intensity inside the car.(3) Based on the research of the simple cable’s electromagnetic effect, the couplingresponse of multi-core wire and cable network with HEMP excitation is studied. Formulti-core wire model, BLT single conductor transmission line equation is replaced by BLTmulti conductor transmission line equation when calculating the cable response. Thequantity of core wires in multi-core cable is reduced to4with the method of equivalentcable-bundle model. It improves the computational efficiency and ensures the accuracy ofresults. For cable network model in vehicle, the electromagnetic topological model isestablished which contains nodes and pipelines. Then link parameters of cable network andelectromagnetic topology BLT equation are determined. With the CST simulation and thefield-to-line coupling model, the results above are used to research the electromagneticeffect of each node in the vehicle cable network.(4) Electromagnetic topology model of shielded wire in vehicle is processed, whichadds the cable shielding layer on the basis of cables and vehicle shell. The method tocalculate the electromagnetic effect of shielded wire is the same as before. It is combinedwith BLT transmission line equation and field-to-line coupling model. The results arecompared with single wire’s to verify the shielding effect. Considering shielded wiregrounding standard and engineering needs, the grounding effectiveness of shielded wire onthe ideal plane is simulated in the CST software. Different grounding resistances anddifferent grounding modes which are single point, double points and multiple points arestudied. A non-terminal grounding technology is proposed, which shows a better effect thanother terminal grounding technologies before. All of the grounding technologies above aresimulated on the shielded wire of vehicle, which demonstrates that the multiple pointsgrounding mode shows better performance in the vehicle.The analysis methods and conclusions in this paper will provide reference for theresearch of vehicle electromagnetic compatibility technology.