Electrode-fall voltages of SF6 and air arcs between electrodes of Fe, W, Cu-W, Cu and Ti in the current range from 10 A to 20 kA

Abstract

Measurements were made of the sum of cathode-fall and anode-fall voltages, i .e. electrode-fall voltage U fall for SF 6 and air arcs at a pressure of 0.1 MPa in a wide current range from 10 A to 20 kA. The arcs were burned between electrodes of iron, tungsten, copper-tungsten, copper and titanium. For each electrode, U fall at a given current was estimated as the arc voltage at the zero gap length between the electrodes, which was extrapolated from arc voltages measured in short gaps with lengths below 3 mm. The electrode-fall voltage U fall of the SF 6 arc proved to be 17.5 V, 13.8 V, 17.5 V, 17.5 V and 17.3 V for the Fe, W, Cu-W Cu and Ti electrodes, respectively. The electrode-fall voltage U fall was affected by the electrode material, while U fall of the air arc is almost the same as that of the SF 6 arc. It was also found that U fall of each arc at a given electrode was independent of current in the above range.