Circuit protecting apparatus including resettable vacuum fuse and switch

Abstract

A current-responsive, resettable, violence-free low fault range vacuum-type switch interrupter is disclosed which is especially designed for series connection with a high fault range current limiting fuse (CLF) to achieve an improved, full range circuit protecting device adapted for use in padmounted, oil filled switch gear apparatus or the like. The resettable switch includes a spring-loaded, over center toggle motive assembly along with a current-responsive, temperature sensitive, bimetallic U-shaped latching element; in the event of a fault, the element deforms and releases the motive assembly to quickly open the vacuum contacts without the violence or oil contamination associated with fuse links. Manual opening of the contacts, and resetting thereof after either manual or fault-induced contact opening, is achieved through appropriate manipulation of an external, trip-free operating handle. The switch further includes a weighted, shock-absorbing element for slowing the contacts just prior to engagement thereof during the switch closing sequence, and a novel, high-impact hammer arrangement for breaking any contact welds during the fault-induced operation of the switch. The resettable switch-CLF combination is synergistically coordinated such that the switch is operated when it experiences the characteristic let through current incident to the operation of the CLF, so as to enhance the overall protective result. In three-phase systems where each phase conductor is separately protected, the respective switches may be advantageously gang coupled to operate together, even if only one conductor experiences a fault.