Theoreticaland Simulation Analysis Of Thermal Characteristics Of Molten Metal Bridge

Molten metal bridge is an important stage before the formation of arc discharge.Arc is the main cause of contact adhesion,and adhesion is also the main failure cause of a contact.Therefore,the research on metal bridge is extremely helpful to the study of the problem of electrical contact failure.In this paper,the molten bridge behavior of metal contact in the process of breaking is taken as the research object,through the technical means of theoretical modeling and simulation research,the thermal characteristics and typical experimental waveforms of molten metal bridge are analyzed.Firstly,the temperature distribution model of metal contact and molten bridge is established based on the principle of heat balance,and the law of temperature distribution of metal contact and molten bridge,the influencing factors of the maximum temperature and root temperature of steady-state molten metal bridge are studied.The influences of bridge radius,bridge length,circuit current and different metal materials on temperature distribution of molten metal bridge are compared and analyzed;The effects of four physical parameters,i.e.maximum temperature,loop current,bridge radius and bridge length,on the thermal characteristics of the steady-state molten metal bridge are summarized.Secondly,the regularity of temperature distribution of non-stationary molten metal bridge is studied;the model of temperature changing with time is established;the changes of temperature and thermal power before the formation and fracture of metal bridge is studied;the characteristics and relations in this process are studied;The influences of breaking speed,bridge radius,bridge length,circuit current and different metal materials on the change of bridge temperature with time are compared and analyzed.Thirdly,based on the finite element simulation software Comsol Multiphysics,the simulation model of the thermal characteristics of molten metal bridge in the process of contact breaking is established;the temperature distribution nephogram and potential distribution nephogram of molten metal bridge at multiple times are obtained;the curve of the temperature changing with time in the molten metal bridge simulation model is obtained;the difference of the temperature changing curve with time between the mathematical model and the simulation model is compared.Finally,based on the typical experimental waveforms of the voltage and contact force of molten metal bridge changing with time,the reason of voltage fluctuation in the rising stage of molten metal bridge is analyzed;the influence of different contact modes of contact spots on the sudden increase of the volume of molten metal bridge isanalyzed;the principle of the temperature drop of the metal bridge caused by the sudden increase of the half diameter of molten metal bridge is analyzed,and the influence of the changing of heat generation power,heat dissipation power and resistivity on temperature is studied;The relationship between the sudden increase times of molten metal bridge volume and the temperature changing is studied.The physical mechanism of the changing process of the voltage gap of molten metal bridge is further analyzed by comparing the experimental waveform with the model curve.The research results of this paper are of great practical significance for analysis of the thermal characteristics physical mechanism of molten metal bridge,and also for the study of electrical contact reliability in the field of electrical engineering.