Effects of Nozzle Shapes and their Positions on Axial Distribution of Electron Density around Nozzle Throat and on Arc Interrupting Capability in Flat-type Air-blast Quenching Chamber

Experimental investigations were performed on electron density of an arc around nozzle throat and the dependence of the arc interrupting capability on the electron density at current zero in a flat-type air-blast quenching chamber. The inlet width W of the orifice nozzle and the axial distance D between the nozzle throat and the tip of upstream electrode were varied. The electron density measured at the current zero has lower magnitude at the nozzle throat than that at other two axial positions for the same W and D. For D=15mm, the electron density at the nozzle throat decreases from 4.2×1019 to 3.5×1019m-3 with a rise in W from 15 to 25mm while growing to 3.8×1019m-3 with W to 34mm. For W=25mm, the electron density at the nozzle throat increases from 3.5×1019 to 4.6×1019m-3 with D from 15 to 25mm. The interruption tests showed the dependence of the failure rate of an arc interruption on W and D same as that of the electron density at the nozzle throat on W and D. The measurement results of the electron density and the failure rate revealed that the failure rate increases linearly with electron density at the nozzle throat at the current zero.