Study of the arc behavior in low-voltage circuit breaker by means of optical and magnetic measurements

The presented study deals with the influence of the contacts materials on the evolution of the arc in low voltage circuit breakers. The commutation from the mobile contact onto the electrode is especially investigated in order to improve the breaking device performances. Hence, to preserve the qualities of the contact, the arc must leave this area as soon as possible. To undertake this study, several diagnostics are implemented. A measuring device is composed of magnetic induction sensors located outside the chamber. It allows the determination of the position and the volume of the arc during the breaking. Optical (ultra-speed camera) and electrical measurements are also performed with the technical support of Schneider Electric. Different current values (assumed peak current of 3 kA, 8 kA and 12 kA) and different natures of materials composing the electrical contacts have been tested. Copper contacts, different contacts on silver base obtained with different processes have been used. Experimental results show the influence of these various parameters on the arc volume and on the transfer of the arc towards the quenching chamber. Indeed, different dynamic behaviors are observed during the current transfer phase.