Determination of the power lost by conduction into the cathode at low current arc
Résumé
The power lost by conduction into copper, silver and tungsten cathodes surrounded by water-cooled brass was determined experimentally. The measurements were made for prolonged short arcs (0.4-1 mm) at low current (2.6-5 A) in argon at 1 atm. The experimental method consists of measuring the temperature reached in the steady state at different points distributed along the electrode axis, fitting the values obtained and calculating the power Pcd supplied to the cathode surface facing the column. With these values of Pcd we calculated the spot radius r and current density j as functions of the electrical power input under the assumption that the spot is circular.