Experimental study of contact opening

In this paper we present an experimental apparatus elaborated in order to study contact opening dynamics under the influence of a strong current. The aim is to have a better understanding of the Lorentz and the blow-open forces exerted on the electrodes of power switches during short circuit fault conditions. This apparatus is constituted by a device allowing us to measure the total force exerted on a static lower electrode and by a system allowing us to study the dynamics of an upper electrode able to move axially. We record, versus time, the current flowing through the contact interfaces, the contact voltage drop, the arc voltage drop, the upper electrode velocity and the forces exerted on both electrodes during the transient period of their opening. First experimental results are presented concerning the dynamics of three kinds of electrode materials i.e. Cu OFHC, AgCdO and AgSnO/sub 2/.