| In recent years,with the rapid development of electric vehicles and their charging equipment,the demand for DC contactor,one of their key electrical components,is also growing rapidly.The DC contactor used by electric vehicles requires high working voltage,small volume and reliable working stability.The traditional DC contactor cannot meet the requirements of electric vehicles at the present stage.It is urgent to develop and design a DC contactor with high power,small volume and better breaking performance.Strong arc will be generated when the dc contactor breaks the high current,and the natural zero crossing of dc arc is different from that of AC arc,which makes the arc extinguishing process of DC arc more difficult.Therefore,it is of great practical significance to study and master the evolution law of arc under different breaking conditions and seek effective measures to shorten arc burning time,so as to guide and improve the development and design of DC contactor products for electric vehicles.Based on magnetohydrodynamics（MHD）theory,the mathematical model of DC arc plasma is established by COMSOL Multiphysics software.The model is coupled with multi-physics processes such as airflow field,electromagnetic field and temperature field.In the simulation model of arc extinguishing chamber,hydrogen medium was filled in the chamber,and external circuits were coupled at both ends of electrodes.At the same time,the moving process of moving contacts was simulated by using the moving grid technology.The whole evolution process of breaking arc in arc extinguishing chamber of DC contactor for electric vehicle was simulated and analyzed.The dynamic process of arc breaking under different influence factors is simulated under the existing simulation conditions.According to the simulation results,the influence of key factors such as different magnetic field intensity,different breaking speed and different current grade on arc motion state and arc voltage is systematically studied,and the influence law of different external factors on arc evolution process is summarized.At the same time,the dynamic characteristics of electric arc when the dc contactor is filled with different gas medium in the arc extinguishing chamber are analyzed.The process of arc breaking in the arc extinguishing chamber with N2,mixed gas H2:N2（2:3）and mixed gas H2:N2（3:2）is simulated,and the influence of different media on arc extinguishing is studied.And compared with the arc extinguishing room filled with H2medium.The research has certain significance for shortening the arcing time of DC contactors for electric vehicles,improving their breaking capacity and optimizing the structure of arc extinguishing chamber. |
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