A numerical model for thermal processes in an electrode submitted to an arc in air and its experimental verification

Energy balance is very difficult to establish for contact electrodes submitted to an electric arc. The energy transferred to the electrodes based on the determination of the liquid and vapor quantities created by the arc root is evaluated by numerical computation, and compared with measurements. The assumption of a concentrated and quasi-circular arc root in air at atmospheric pressure is confirmed by high-speed laser cinematography. An axial symmetry can be adopted in the numerical model for both arc root and electrode. This model takes into account the huge power focused onto a small area of the electrode surface, producing intense surface heating, liquefaction and evaporation, and the subsequent formation of a crater. A method is presented to overcome the difficulties related to state changes and ablation problems. The model is used to account for the results obtained with a previous experimental device designed to directly obtain the amount of liquid and vapor formed.<>