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). A simple method allowed us to asses the value of the blow open forces. We have also studied the
influence on the measured forces of the contact material, the amplitude of the current pulse, the polarity of the
electrodes. For the electrode materials tested in this study (Ag-SnO2, Ag-CdO and Ag-CW),
it appeared that forces exerted on cathode and anode are of the same order and that
AgSnO2 use allows to have higher forces (and longer opening phase) than for the two other
materials and then may decrease the contact welding.