| EMU has a wide range of internal equipment and cables which intertwine together, resulting in the complexity of the mechanism of EMI coupling in the limited space of EMU. EMI coupling can disturb the cab signal and influence the operation of the equipment, therefore the improper arrangement of cables may cause electromagnetic interference. Cables are mostly set in the groove or shield. This thesis carries on the research of crosstalk coupling and radiation coupling by theoretical analysis, simulation modeling and testing, analyzes the electromagnetic compatibility and anti-interference measures as well as proposes routing suggestions.We first build up a research method on cable coupling, field cable coupling and radiation, then carry out the theoretical analysis according to the method. According to the theory of transmission line, we deduce the distributed parameter of unshielded cable, shielded cable and twisted-pair cable respectively which used as the base of MATLAB programming and quantitative analysis of different parameters for the influence of cable crosstalk. At the same time, EMC studio is used to simulate and verify the consistency between the simulation results and the theoretical analysis. Field line coupling and radiation contains two independent transmission line problems. We analyze both external and internal transmission line and come to a conclusion on the response of voltage and current of the shielded cable core wire under the condition of external incident field. The analytical formula of electromagnetic field around the conducting wire is derived by using the Maxwell electromagnetic field formula.On the basis of the theory above, we set up a test platform to simulate the internal working condition of EMU, study the crosstalk of the cables inside the groove and test the influence of different grounding modes on the crosstalk. The result is compared with the simulation model which verifies the validity of the simulation model. Therefore, the simulation model is used to study the influence of different parameters of the groove on the crosstalk between the lines. We set up a simulation model to discuss the influence of shielding layer grounding mode of high voltage cable on the cable crosstalk between high and low voltage wire groove according to the actual parameters of the actual layout of cable harness and cable car of the EMU. The result shows that when there is enough space to set the high pressure wire groove and the low pressure wire groove, the influence of the crosstalk between the high voltage circuit and the low voltage circuit will be less.By analyzing the test results in the actual EMU and comparing with the simulation results in view of the low frequency magnetic field radiation problem of high voltage cable, the correctness of the simulation model is verified. Because of the harm of the low frequency magnetic field to human and equipment as well as the limitation of the heart pacemaker and other equipment, shielding casing is used to reduce the radiation field in the actual arrangement of the EMU set. Using simulation model to study the influence of different shielding casing parameters on low frequency cable radiation field, simulate the three different excitation source of actual EMU. Model the two situation of the shielding casing to study the low frequency magnetic field radiation for high voltage cables set in the passenger compartment of EMU. The result shows that shielding casing can greatly reduce the radiation field of the cable but the maximum limit of harm will still not be reached without the shielding casing.Based on the research of cable crosstalk and field line coupling, the specific measures to reduce electromagnetic interference are presented. |
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