| The electric arc is one of the important research topics in power system,welding,lighting,metallurgy and other fields.Especially in the research of switching apparatus,arc has a direct impact on the breaking performance,electric life and other important indicators of switching apparatus.At present,the research of arc mainly focuses on the stable combustion process and arc extinguishing process,but the formation process of arc is seldom paid attention to and studied.The study of arc formation process not only complements the theoretical model of arc forearc link,but also explore the unstable factors affecting arc formation process and provide solutions for arc extinguishing.However,the arc formation process takes a short time,the temperature range is large,and the central temperature is as high as tens of thousands of degrees Celsius.Complex physical processes occur in the tiny spatio-temporal scale,which makes it difficult to directly measure and observe them completely,which brings difficulties to the study of arc formation process.Therefore,it is of great significance to study the forming process of electric arc,especially the forming process and model of electric breakdown arc.Firstly,this aricle devides the the formation of arc into thermal breakdown and electrical breakdown according to the ionization factors of gas breakdown phenomenonbas.According to the characteristics of the forming process of electric breakdown arc the forming process is devided into three stages:the generation of high voltage stage,intermittent breakdown stage and arc transfer stage.And a three-stage model of electric breakdown arc formation process is proposed.At the same time,aiming at the research requirement of electric breakdown arc formation process,a series DC arc generating device was proposed and successfully applied in the experimental research.Secondly,in the stage of high voltage generation,the equivalent circuit of high voltage generation is established and the analysis and estimation method of arc ignition voltage is proposed.The influences caused by power supply voltage,load resistance,current limiting resistance,distributed capacitance and other different circuit parameters of output voltage are studied,and the accuracy of estimation of arc ignition voltage is verified by simulation and experimentThen,in the stage of intermittent breakdown,the arc intermittent breakdown model is proposed.According to the breakdown voltage and the breakdown arc energy,the effects of the interelectrode distance and the starting current on the breakdown characteristics are analyzed.And the simulation results are in good agreement with the experimental results,which verifies the effectiveness of the model.At the same time,the relationship between interelectrode distance and breakdown voltage as well as breakdown arc energy,and the boundary conditions of the electric breakdown are given.Finally,in the stage of arc transfer,the arc radius diffusion model is given on the base of the arc energy balance equation,and the influence of different parameters on the arc dynamic volt-ampere characteristic transfer is analyzed.The relationship between interelectrode distance and arc transfer response time as well as arc current is given,and the simulation results are in good agreement with the experimental results.In a word,the three-stage model of electric breakdown arc formation process proposed in this paper is suitable for describing the formation process of electric breakdown arc.The forming process of electric breakdown arc also determines the stability of electric arc and can be used in various practices. |
