Contribution to the study of interactions between an atmospheric pressure arc root and Cu, Ag, or Ag MO electrodes

The various phenomena governing the cathodic or anodic roots of an arc burning in air at atmospheric pressure are addressed. The distribution of the current density at the cathodic and anodic roots is evaluated. It is concluded that for the range of arc currents where the method remains valid, the anode, as well as the cathode, works in the concentrated spot regime leading to gross-melting phenomena. The method is based on an analytical study of the main components of the force exerted by the arc on an electrode. It is, then, possible to make the assumption that beyond a minimum arc current value, the Lorentz force due to the constriction effect of the current lines entering the electrode becomes the preponderant part of the total force. From the expression of the Lorentz force and the measurement of the total force, and with the use of an original device developed at LGEP, the spot radius can be deduced as a function of arc current