Induced radial velocity in nonstationary electric arcs

An analysis is presented of the effects of induced radial velocity on the thermal behavior of a nonstationary electric arc. An interrupted dc arc is simulated by treating the linearized equations for a cylindrical plasma, initially at a uniform temperature, when the wall temperature is suddenly changed by a small amount from the gas temperature. Due to compressibility, a radial wave motion is set up within the gas which causes rapid interior temperature changes on a time scale much smaller than the conduction time constant. For example in a 5-mm diameter SF6arc, which is initially at a temperature of 11 000°K, the central temperature will change by 20 percent in 1 µs, while the conduction time constant is 100 µs. The possible importance of this behavior for circuit breaker arcs is discussed.