Arc quenching current limiting device including ablative material

Abstract

A current limiting device for protecting electrical circuits has a case and a pair of separable electrodes disposed within the case. Each electrode has a plurality of openings with an ablative member abutting the openings at an outer surface of the electrode. A spring is disposed between each ablative member and the case for urging the electrodes together. When the electrical current exceeds a predetermined setpoint the electrodes separate and an arc is created between the electrodes. The arc heats the ablative member causing expulsion of gasses which further increase the gap resistance and cool the arc to thereby quenching the arc. In a second embodiment of the current limiting device, one of the electrodes is a fixed electrode. The ablative member is disposed about a surface of the moveable electrode with a plurality of legs passing through a plurality of openings of the moveable electrode and in contact with an inner surface of the fixed electrode. A plurality of ablative member springs urges the ablative member against the fixed electrode and a plurality of electrode springs urge the movable electrode against the fixed electrode. In the second embodiment the efficiency of the expulsion of gasses is increased because the legs of the ablative member are positioned within the arc.