Simulation Study On The Effects Of Multiple Physical Factors On DC Contact Arc And Electric Erosion

In recent years,with the rapid development of new energy fields,the demand for DC distribution system in electric vehicle,aerospace,photovoltaic power and other industries is increasing.As a key component of breaking circuit,DC switch has been widely used,but at the same time,it has higher requirements on its reliability and electrical life.The contact system of DC contactor is one of the most critical components.When the circuit is disconnected,the high temperature arc between the contacts will erode the contact material,which will seriously affect the performance of switching appliances.Therefore,exploring the DC arc characteristics and contact erosion under arc action has important practical significance for improving the performance and service life of DC switching appliances.First of all,based on the principle of energy conservation,combined with hydrodynamic equation and electromagnetic field equation,the simulation model of arc and contact pool is established,and the difference of arc and contact erosion caused by gas medium is explored.By the thermal physical parameters brought into different gas media,the arc characteristics between contacts and contact erosion under four different gas media:He,H₂,N₂ and air are simulated and solved.the simulation results show that the characteristics of arc under each media are different when arc is burning stably,in which the maximum temperature of arc is:He>H₂>N₂>air;in the same arc burning time,the erosion of arc on contact under different gas media is significantly different.Second of all,based on the traditional heat transfer model and the treatment method of material phase change,considering the property of contact material changes with temperature,the erosion of arc on contact and its influencing factors are explored.With arc in air as the research object,the temperature distribution inside the copper contact,the forming process of melt pool and the flow inside the contact pool are solved by using COMSOL finite element software.The influence of arc current,contact pitch and contact material on contact erosion was analyzed by controlling variables.The simulation results show that under the action of arc,the temperature of contact surface rises rapidly and melts to form a melting pool,the boundary of the pool expands continuously in a circular arc,and the liquid inside the pool flows due to Marangoni effect.In addition,the changes of arc current,contact pitch,contact material and other physical factors can also affect the erosion of contacts to varying degrees.In the end,two erosion mechanisms:evaporation and splashing are discussed.Based on the improved probability statistical splashing calculation method and the data obtained from the simulation model,the erosion amount of Ag,Cu,W,Cr contact materials is calculated.The results obtained in this paper are compared with those in the published literature,which verifies the feasibility of the simulation calculation model,and can provide some reference for improving the performance of DC contactors.