Arc resistance increasing during DC interruption using SiO₂/Si₃N₄ mixture powder as arc interruption medium

This paper applied mixture powder of silica-sand(low-purity SiO₂ sand) and silicon-nitride(Si₃N₄) as new direct-current(DC) arc interruption medium. The present research carried out theoretical calculation of gas properties for SiO₂/Si₃N₄ mixture arc and a DC arc interruption experiment using the mixture powder. As a calculation result of gas properties, thermal conductivity was increased with Si₃N₄ vapor admixing into SiO₂ vapor. In addition, arc resistance r_arc was increased under condition using the SiO₂/Si₃N₄ mixture powder compared to r_arc under condition using only the SiO₂ powder. The arc resistance rise could be explained based on increase in the thermal conductivity of the arc due to the Si₃N₄ vapor admixing and consequent rise in thermal energy dissipation from the DC arc.