Mixture of Si₃N₄ powder and SiO₂ sand as novel DC arc quenching medium for improvement of current limiting performance of model electric fuse

A current-limiting and consequent direct current (DC) arc interruption requires an increase in arc resistance <?CDATA rₐrc?> r a r c for a DC fuse. Flattery silica (SiO 2 ) sand has been used as an arc quenching medium in fuses for decades. However, there are few reports about a novel arc quenching medium which enables more <?CDATA rₐrc?> r a r c increases compared to flattery SiO 2 sand. This paper uniquely selected a novel arc quenching medium based on the following material properties: (1) electrical resistivity and thermal conductivity in the solid phase, (2) the possibility of <?CDATA rₐrc?> r a r c increasing in the gas phase, (3) the possibility of electrical insulation after re-solidification, and (4) the cost of materials. As a result, we originally selected a powder mixture of silicon-nitride (Si 3 N 4 ) and flattery SiO 2 sand as a promising novel arc quenching medium. Therefore, DC interruption experiments were performed using a Si 3 N 4 /flattery SiO 2 sand powder mixture under different Si 3 N 4 concentration conditions. As a result of 1000 A DC arc quenching experiments, the utilization of Si 3 N 4 powder with the flattery SiO 2 sand successfully increased the arc resistance <?CDATA rₐrc?> r a r c during the arc quenching process. The increasing Si 3 N 4 concentration exhibited a further increase in <?CDATA rₐrc?> r a r c during the arc quenching process. As a result of the <?CDATA rₐrc?> r a r c increase, the arc quenching time was significantly shortened to 30 ms for 30 wt.% Si 3 N 4 conditions from 54 ms for the SiO 2 sand conditions. In addition, utilization of Si 3 N 4 powder achieved high insulation resistance over few MΩ after DC arc interruption. The above results clearly indicate that utilization of Si 3 N 4 powder with flattery SiO 2 sand can increase the DC interruption performance of the fuse.