Abstract: A time-lag fuse with improved breaking capacity is made of double-tubular construction comprising an inner tube made of a material having high thermal conductivity and low thermal impact resistance and an outer tube made of a material with low thermal conductivity but high thermal impact resistance. No arc-quenching material is required and greater safety is afforded when the fuse is subjected to an overload current.

Abstract: A time-delay fuse is provided comprising a glass or ceramic tube sealed at both ends with sealing means such as, e.g., ferrules. An elongated generally cylindrical core member, made from a highly heat conductive material (a sintered blend of aluminum oxide and magnesium oxide spinel), is diagonally disposed in said tube and rigidly fixed at both ends in intimate contact with said sealing means. The fuse also comprises a wire strand spirally wound on said elongated core member. The wire strand is made by winding a first metallic wire element over a second mutually fusible wire element and is soldered at both ends with a high melting solder element.