Аннотация
The investigation of phenomena of the electrical arc transition from metallic to gaseous phase is very important for the optimal choice of parameters of switching apparatus. The initial arc stage is evaluated by vapors from the ruptured bridge in the contact gap. Cathode and anode phenomena such as ion bombardment, thermoelectronic emission, inverse electrons flux, evaporation, radiation, heat conduction etc. are considered in dependence on time, current, opening velocity, parameters of the gas and contact materials. The conditions of the arc transition from one phase to another are formulated in terms of above characteristics and increasing of gas ionization level. This approach enables one to explain the transition from the metallic anode dominated arc to the gaseous cathode dominated arc and to estimate corresponding arc erosion during each phase. The mathematical model is based on the special Stefan problem for the short electrical arc, liquid and solid contact zones with nonlinear boundary conditions depending on the unknown temperature. The Stefan condition is written in the generalized form. It contains the special ejection coefficient which takes into account the ejection of a portion of the liquid metal from the melt due to the action of electromagnetic force, metallic vapor pressure and Marangoni effect. The values, and are in keeping with two-phase, one-phase and the phase with a partial ejection of the liquid phase correspondingly. To solve this problem, an iterative method of majorant functions has been developed, which makes it possible to obtain sequences of overestimated and underestimated temperatures in the liquid and solid zones of the contact area, as well as the corresponding values of the erosion values.