Research On Crosstalk Between Cables On Board In High-Speed EMU

High-speed EMU is a large and complex system because of its limited space and intensive equipment. The arrangement of different types of cables has a large impact on electromagnetic compatibility. There have been a lot of researches working on the cable coupling. However, cable on board is arranged in metal groove and it has special characteristics. Metal structure of groove will cause the change of electromagnetic field around the cable and distribution parameter between cables in the groove, further affecting crosstalk circumstances. Therefore, more meaningful works in the area of the cable coupling of high-speed EMU is urgently needed. In this thesis, the problem of cable coupling in high-speed EMU was analyzed by theory, experimental verification and simulation analysis. And the cable layout optimization scheme was proposed.Firstly, in order to predict electromagnetic compatibility of EMU system, object-oriented modular modeling method and the concept of object properties were put forward. According to the electromagnetic characteristics of the devices, the objects with the same electromagnetic properties were defined as an object model which can use the same analytical method. Hierarchical modular model was established for EMU system. In the analysis of a particular object, only operate on the relevant properties of the object model, the analysis result of electromagnetic compatibility can be obtained.Secondly, crosstalk coupling of unshielded cables and shielded cables was analyzed. Expression of crosstalk coefficient was derived. The relationship between crosstalk coupling coefficient and different parameters was analyzed by MATLAB for the crosstalk prediction. The fundamental reason for crosstalk is the distributed parameter of cables. The formulas of distributed inductance and capacitance parameters were derived in different actual situations by image theory.Finally, based on the above theories, crosstalk simulation model of cables was set up. The simulation result showed good consistency with theoretical analysis and measurement result. Coupling models that cables located in the same groove and in different grooves were established based on this modeling method. At last, according to a specific cable arrangement on board in EMU, cable coupling model in low-voltage groove and between high-voltage and low-voltage groove were established, respectively. The influence of groove structure on cable coupling was explored, and two different grounding method of groove for comparison.Simulation results showed that the maximum crosstalk of low-voltage cables in groove is 20dB lower than that without groove. The cover and clapboard can also reduce some crosstalk. The groove at the side of high-voltage cables can reduce crosstalk between high-voltage and low-voltage cables. The crosstalk coupling between them on EMU is -80dB or less, will not affect each other. Groove with equally spaced grounded and grounded near the equipment has little effect on crosstalk. The results are of great value for practical cabling in the research and development stage of EMU.