Reattachment model of the anode spot of a non-transferred DC arc

Summary form only given. Anode attachment of a non-transferred DC arc performs periodic motion: motion downstream, breakdown a cold gas layer that separates main arc column somewhere upstream, reattachment to the new anode spot, motion downstream etc. The phenomenon of reattachment the anode spot has not been completely understood yet. A simple model of the anode reattachment is suggested. Based on a fact that electron temperature doesn´t drop as low as the heavy particles temperature does, it is assumed that some residue electrical conductivity (on the level of 10^-2 Ohm^-1m^-1) exists in the cold anode layer. It is shown that increasing in time the voltage drop across the layer leads to a fast development of the overheating instability. This creates in an upstream location, where the voltage drop is the highest, a well electrically conductive column and to reconnection of the arc to this new attachment. Simple estimations of the amplitude of the voltage oscillations and their frequency correspond to experimental data.