Simulation And Analysis Of Magnetic Field In EMU Train

High Speed Rail was the only viable transport solution capable of reducing costs,accidents,energy consumption and increasing operation speed,punctuality rate,so it was a common trend of railway development in the world.As the operating speed and power of the train increased,the low-frequency magnetic field in the car further attracted attention.The sources of low-frequency magnetic fields in EMU cars mainly included traction currents of up to several hundred amps or even thousands of amps,and high-power equipment under the train.Therefore,in this thesis,I focused on the distribution rule of the low frequency magnetic field the In-car magnetic field,through electromagnetic simulation research and in site test.Finally,based on electromagnetic simulation,I analyzed the influence of the car body structure on the measurement of the magnetic field in the car.Firstly,most of the traction current of EMU trains flowed back to the traction substation through rails and backflow lines.A small part of the backflow current formed backflows between the vehicle bodies or the ground carbon brushes,which may affect the electromagnetic environment in the car or disturb the normal operation of the grounded carbon brush.In this thesis,the ANSYS Simplore simulation software was used to establish the simulation model of the car body return equivalent circuit of the two types of EMUs based on the grounding method of the CRH2 and CRH380 AL EMUs and the main circuits of the cars.Based on the simulation results,the specific distribution rules of the operation ground current,protective ground current and vehicle body backflow of two different types of EMUs were obtained.Based on the research results of the EMU car body backflow current,this thesis focused on the research of the In-car magnetic field generated by the EMU traction current,the rail return current and the car body backflow.The ANSYS Maxwell electromagnetic simulation software was used to establish a finite element model of the EMU car body for simulation to analyze the distribution of magnetic field in the car.The results showed that the strength of the magnetic field in different cars was different,but the spatial distribution characteristics were consistent.The magnetic field strength were the highest at the windshield in the EMU compartment,the magnetic field near the window was greater than the magnetic field away from the window,and the magnetic field near the bottom of the car was greater than that far away from the bottom of the car.In addition,an actual measurement of magnetic field in EMU was performed to obtain the specific value of the magnetic field in the car under different operation conditions of the EMU.Comparing the simulation results with the test results showed that the simulation and measurement data have good consistency,which further verified the feasibility of the simulation.Finally,During the measurement of the spatial magnetic field in the EMU,the environment inside the car affected the final test results by affecting the antenna coefficient of the measurement antenna.In this thesis,the simulation method was used to simulate the actual test process by establishing antenna and EMU compartment models.Through the data analysis of the simulation results,the uncertainty factor value of the influence of the environment in the car on the magnetic field measurement was obtained.