High voltage, high current fuse with combustion assisted operation

Abstract

A high voltage fuse comprises one or more fusible strips or wires (fusible elements) electrically connected between nonfusible external electrical connection means with at least one portion of the fusible element ('a rapid melting portion') being designed to melt open when the current exceeds a given value for a given period of time. The fuse further comprises exothermic material, disposed on electrically-conductive wire, which is placed adjacent to portions of the fusible element. Electric circuit connection means connect the electrically-conductive wire to electrically opposite sides of the rapid melting portion. The electrical circuit connection means provides for either parallel or series connection of the wire surrounded by the exothermic material. In operation, during the passage of a sufficiently high current, an arc develops in the immediate vicinity of the rapid melting portions and the voltage drop occurring across this arc supplies power to the electrically-conductive wire which ignites the exothermic material so as to either blast or melt away specific remaining portions of the fuse. As a result, a plurality of series connected arcs are formed so that the sum of the voltages across the arcs increases to a level sufficient to bring the current through the fuse to a zero value in a short time.