Influence of Gap Length between Electrodes and Size of a Closed Chamber on Internal Pressure-rise due to Arc

Abstract

This paper describes the phenomenon of internal pressure-rise due to arcs in the air. The electrodes used were made of aluminum, copper and iron. The arcs were ignited in a closed chamber with current of 12.5kA and duration of 0.1s. Firstly, the internal pressure-rises were measured with changing the gap length between electrodes in the range of 5 to 75mm. As a result of the evaluations of the efficiency factor, which was defined as the amount of the maximum pressure-rise divided by the total arc energy, it was clarified that the efficiency factor in the case of the aluminum was strongly influenced by the gap length. This was presumably caused by the change in the oxidation reaction energy of the vaporized electrodes with the gap length. Secondly, the internal pressure-rises were measured with changing the size of the chamber in the range of 0.32 to 0.71m³ in volume. Consequently, it was proved that maximum pressure-rise at a certain size of the chamber exceeded the one estimated with taking into account only the volume change of the chamber. This was presumably attributable to the resonance effect.