Arc root mobility during contact opening at high current

This paper presents a test system, designed for the investigation of short circuit arcs related to miniature circuit breakers operating in a 240 Volt, ac supply. An optical fibre imaging system presented previously is used to identify arc root motion, with short circuit current up to 6kA. Two methods arc used to measure contact motion, a non-contact linear position sensor, and the optical fibre array. The optical fibre array uses software image processing to identify the position of the arc roots in the arc chamber. The identification of the arc roots allows for a study of the arc immobility at the initial stages of the event. Initial results are presented on the effect of supply polarity on arc root motion.