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For break arcs occurring between Ag and Ag/SnO$_2$ 12,wt% electrical contact pairs, the electrical conductivity, viscosity and specific heat at constant pressure are calculated as thermodynamic and transport properties. Mixture rates of contact material vapor are 0%, 1%, 10% and 100%. Influence of the contact material on the properties is investigated. Temperature for the calculation ranges from 2000,K to 20000,K. Following results are shown. When the mixture rate is changed, the electrical conductivity varies at lower temperature (< 10000,K), and the viscosity and specific heat vary widely at all temperature range. The electrical conductivity is independent of the mixture rate when the temperature is exceeding 10000,K. The thermodynamic and transport properties are independent of the kind of the contact materials.
Xingwen LI Shenli JIA Yimin YOU Zongqian SHI
The paper is devoted to the experimental study of the arc plasma characteristics in SF6, N2 and CO2. To one flexible model of gas circuit breaker, short circuit experiments have been carried out considering the influence of contact gap (4–12 mm), gas pressure (1–5 atm), short circuit current (1–5 kA effective value) as well as gas species particularly. During the experiments, the arc image, arc current and arc voltage are recorded by the high speed camera, shunt and voltage transducer, respectively. It demonstrates that to the above mentioned three kinds of gases, the arc radius and arc voltage increase with the short circuit current and gas pressure normally; however, under the same experimental conditions, N2 arc holds the minimum arc radius and the maximum arc voltage, and the arc voltage of SF6 arc is the lowest.
Qiang MA Mingzhe RONG Anthony B. MURPHY Yi WU Tiejun XU Fei YANG
This paper focuses on the numerical and experimental investigations of the influence of two polymers (PA6 and POM) on the arc behavior during arc motion process. The mathematical model of 3-dimentional air arc plasma considering the ablation of lateral walls is built based on magnetic hydro-dynamics (MHD). By adopting the commercial computational fluid dynamics (CFD) package based on control-volume method, the above MHD model is solved and the distribution of temperature field, concentration field, flow field and electrical potential field in the arc chamber are calculated. The simulation results indicate that the vapor concentration behind the arc column is higher than that in front of the arc column because of the existence of "double vortices" in the arc chamber. The use of polymers causes the maximal arc voltage increase 16.2% with POM and 18.9% with PA6 in this case and causes the average arc velocity increase 15.8% with POM and 21.1% with PA6 in this case. The experiments are also carried out to study the influence of polymers on arc voltage and arc root position in the arc chamber during arc motion. The experimental results prove the validity of the numerical investigation.