The repulsion of electrical contacts crossed by short-circuit currents

The study of forces exerted by an arc on silver based electrical contacts is important in order to understand the dynamic phenomena concerning the opening or closing phases of contacts in a variety of switching applications. For that, an experimental device was built. It allows us to measure accurately the force on the static electrode and the displacement of the mobile electrode (and hence the force on it) when the two contacts, crossed by a current pulse (from 0 to 4 kA) separate. The measured forces are the sum of Lorentz magnetic forces (constriction force and loop effect force) and blow open forces due to the arc plasma (evaporation and (or) decomposition of contact materials). We have studied the influence on the measured forces of the contact material, the duration of the current pulse and the polarity of the electrodes.