Analyse And Optimize Of The Cooling System Performance Of The EMU Ground Power Inverter Unit

In recent years, with the development of high-speed railway, the EMU is favored by more and more people because of its advantages of efficient, fast, stable, etc. With the development of technology, the power electronic devices on locomotives are developing to small and dense, and power is increasingly high. When the power electronic devices work, they will produce quantity of heat, if there have not suitable radiation measure, will make the temperature of chip rises, if the temperature is over than the junction temperature, will make them abnormal.The discussion studies the cool problem of the EMU ground power inverter unit, the heat, which produced by the power electronic devices work, passes to the heat sink substrate by thermal grease, then passes to the number of fins on the heat sink, fins conduct convective heat with a certain flow air generate by the centrifugal fan, the heat will be brought into the environment by the air though air duct, thus complete the entire cooling process.By comparing the experimental results with the numerical results of the inverter unit when working at room temperature, the maximum temperature of the heat sink substrate was found consistent upward trend, the maximum temperature deviation within 5%, to verify the accuracy of the numerical model.In extreme conditions to simulate the cooling system found in the original and can not meet the cooling needs. The influence of different external conditions(different air volume, different fluid flow conditions) and the radiators structural parameters(length of the fin, height, spacing, number) of the heat dissipation property on the basis of the numerical simulation.The results show that: the larger air volume, the lower temperature of the heat sink substrate, and the better the cooling effect of the cooling system, with the increase of air volume, the temperature rise of the heat sink substrate decline slowly; state of fluid flow from laminar flow to turbulent flow can improve the cooling effect of the cooling system; the larger of the value of length, height, numbers of radiator fin, the better the cooling effect of the cooling system, but the downward trend of the temperature will gradually slow; radiator fins gap impact on the cooling effect of the convective heat transfer coefficient depends on the room and the fluid flow resistance of the fin, the fin spacing increases, leading to convective heat transfer coefficient decreases, so reducing heat dissipation, while reducing the resistance to fluid flow between the fins, improve thermal performance of the radiator, through the combined effect of two factors, the heat radiating fin spacing to achieve optimal performance when the 4.5mm.Through the method of CFD, analysis the main factors that affect the cooling performance of the cooling system, and provide guidance for the design of the cooling system.