GB1283766A - Electrical inductive apparatus - Google Patents

Abstract

1283766 Fusible cut-outs WESTINGHOUSE ELECTRIC CORP 18 Sept 1969 [1 Oct 1968] 46091/69 Heading H2G [Also in Division H1] A fuse assembly suitable for use in a liquid immersed transformer comprises an elongate tubular housing 174, formed of an insulating material, having electrodes 180, 182 disposed at the tube ends 176, 178 respectively. A solid liner, 184, of water vapour evolving arc quenching material such as boric acid extends along the length of the tube defining a square or rectangular cross-section arc passageway through which the fuse element 189 extends. The fuse assembly is sealed at one or both ends by frangible seals 191, 192 held in place by the electrodes 180, 182 which have openings axially aligned with the arc passageway such that, when an overcurrent of about a factor of ten occurs, the element 189 melts and an arc occurs along the length of the passageway resulting in the production of gases by the inorganic liner, including steam, which result in the fracture of the frangible seals and an escape of the gases from one or both ends of the tube, which in the process extinguishes the arc. A sub-liner, 190, may be provided which is of arc quenching material such as polyvinyl chloride which does not liberate water vapour when subject to the heat of an arc, the purpose of this liner being to extinguish arcs caused by overcurrents of between three to six times the normal load without breaking the frangible seals. In a further embodiment the fuse 92 (Fig. 3) is mounted inside a "plug in" type fuse holder 102 which includes an insulating receptacle 104 and a removable portion 106 to which the fuse assembly 92 is attached. The fuse 92 used in this embodiment is similar in internal construction to the one described except that it contains no frangible members being firmly sealed at its upper end and open at its lower end where it fits into a removable condenser 140 such that the gases discharged from the fuse assembly 92 will be confined to the condenser which may include copper screens 142 for causing the ejected steam to condense. Such an arrangement is useful when the fuse assembly is immersed in a liquid filled transformer as the gases are prevented from contaminating the liquid dielectric.