Modeling the ignition of high-current high-pressure arc discharge in a cold setup

The ignition of a 200 A atmospheric-pressure argon arc in a setup where the electrodes are initially cold but are rapidly heated by the arc is simulated with the use of the extended model of non-equilibrium near-cathode high-pressure plasma layers. Two limiting cases are considered: one in which the supplied power increases very slowly and the ignition process proceeds through a sequence of quasi-stationary states, and the case of fast ignition, in which the external circuit is instantly switched on at its nominal operating parameters. Three discharge models are used: a stand-alone model of the cathodic part of the discharge; a model with the arc bulk simulated in the local thermodynamic equilibrium (LTE) approximation; and a model with the arc bulk simulated in the two-temperature (2T) approximation. Boundary conditions for the plasma temperature in the LTE model are similar to those for the electron temperature in the 2T model, which is different from the conventional LTE models. The modeling results describe three phases of the arc ignition: the abnormal glow discharge, an arc with a cathode spot, and an arc with a diffuse cathode attachment. The temperature inside plasma balls (bright small plasma regions adjacent to cathode spots) reaches values of the order of 10 eV. The distributions of the plasma temperature given by the LTE model are relatively close to the distributions of the electron temperature given by the 2T model, including at low currents. Results on the glow-to-arc transition, given by the LTE and 2T models, are rather close as well.