Double tubular time lag fuse - has inner tube made of high thermal conductivity, low shock resistance material and outer tube with complementary characteristics

摘要

The disadvantages inherent in fuses which contain arc-quenching fillers in the fuse tube can be eliminated by fuse construction which does not require the use of arc quenching fillers. Yet, the fuse exhibits excellent breaking capacity and time-lag behaviour, and an overload current can be interrupted in a fraction of a second without explosion of the tube and while maintaining the stability of the fuse. The fuse comprises a fusible element (1) such as a conductor metal wire, and the like, disposed within an inner tube (3) which is, in turn, disposed within an outer tube (5) which is coterminus with the inner tubular member. The ends of the tubular members are capped with a pair of ferrules (7,7) to seal the double- tubular fuse while maintaining electrical contact with the fusible element. The fusible element is thus disposed within the empty tube (3) and no arc-quenching filler is employed. The inner tube is of a group comprising fosterite, steatite or talc, and the outer tube of cordierite or lithcium ceramic.