The evolution of high current D.C. arcs on rotating anodes

Abstract

In this thesis the results of a program of research on the evolution of high current d.c. arcs in air at atmospheric pressure are presented. A technique was developed suitable for the study of high current arc discharges, and in particular of the anode properties of such discharges. The apparatus incorporated an electrode system containing a rotating anode with high precision control and monitoring facilities. Research was carried out in the current range 10 to 1500A for electrode separations of up to 15mm and surface speeds up to 32ms⁻¹. Two new transitions in arc properties were discovered and investigated in detail for discharges burning between fixed thoriated tungsten cathodes and moving anodes of copper, nickel, stainless steel and aluminium. Discharge properties in the specified current range were studied and the transitions identified were placed in context in the evolution of the high current arc discharge. The experimental technique developed proved to be eminently suitable for studying the detailed structure of high current arcs. The results obtained revealed a number of important avenues for further research into the properties of high current discharges and suggested several diagnostic techniques which should greatly enhance the capabilities of the apparatus.