Core fluctuations of a gas-blast circuit-breaker arc

High-speed photographs have been taken of the luminous core of an AC arc in an orifice air flow. The arc area is normally directly proportional to the current. In this case the luminous core areas can be correlated by the parameter (r c 2 P 0 0.5 /I(1- alpha ), which is derived from an integral analysis of arc behaviour. The analysis includes the influence of enthalpy flow, kinetic energy transport and, in an empirical fashion, radiation. Under some conditions, however, regular oscillations in arc diameter are observed. These are found to reduce the interrupting ability of the test head.