COMPOSITE FUSE ELEMENT FOR A HIGH VOLTAGE CURRENT LIMITING FUSE

摘要

FUSE ELEMENTAbstract of the DisclosureA fusible element for a current limiting fuseincludes two silver ribbons, each provided with a plurality ofholes spaced apart along the length thereof which definepoints of reduced cross sectional area, one of these ribbonsincluding a conventional "M" spot consisting of a body of lowmelting temperature alloy, such as tin-lead solder, inintimate contact with the silver ribbon. One end of each ofthe silver ribbons is joined to a respective end of acentrally disposed tin wire element by a copperinterconnecting member. This tin wire central portion of thefusible element has a melt I2t which is equal to or greaterthan that of the silver ribbons in series with it. The time-current characteristics of this fusible element at highmagnitude fault currents and at low magnitude overloadcurrents are determined respectively by the fusible points ofreduced cross sectional area of the silver ribbons and by the"M" spot of one of the silver ribbons in the same way as in thefusible elements of known current limiting fuses. However, atintermediate fault currents, the tin element initiates meltingof the fusible element much faster than a fusible elementusing only a perforated silver ribbon and a conventional "M"spot.