The energy input from the arc to the contact surface is a decisive factor on erosion of contact materials. In order to improve the modelling of the erosion process

it is imperative to measure the instantaneous current density on arc root. Breaking experiments with cylindrical AgMeO contacts were carried out in the current range from 200 to 1800A peak. Arc root diameters and apparent current densities were evaluated from high speed camera observations and SEM micrographs.