Characteristics of Arcs Between Porous Carbon Electrodes

Arcs between carbon electrodes present some specific differences compared with metallic arcs. The arc voltage is higher, but does not attain a stable value displaying large fluctuations. Indeed, the arcs are produced by the direct sublimation of the electrodes, without passing through a molten phase. The arc production is also facilitated by both circuit breaking and electric field breakdown. In this paper, arcing has been examined under various conditions (voltage, current, and opening or fixed interelectrode gap) and particular attention has been given to the ability of the system to sustain the arc due to reignition. Small-angle X-ray scattering has been used to examine the formation of particles within carbon arcs and again the results are different from what is found with metallic electrodes, the particles being larger with rougher surfaces. The ultimate aim of this paper was to gain new knowledge concerning these arcs and their consequences for electrical safety (arc faults in wires).