Interruption Capacity

The ability of the fuse to clear short-circuit currents safely is called its interruption capacity. The interruption capacity is listed as the maximum number of amperes that the fuse can safely clear. The interruption capacity of modern current-limiting fuses may be as large as 200,000 A. Fuses can also be used in the power distribution system for the expressed purpose of providing interruption capacity for protecting the system equipment and switch gear against large short-circuit currents.

Both the single-element and the dual-element fuse provide this safety feature by encasing the short-circuit element in silica sand in both types of fuses. When the short-circuit current is applied to the short-circuit element, tremendous amounts of heat are built up while the element is melting. If this heat is allowed to build up, gases can be released when the metal is melted and cause the casing of the fuse to rupture. When silica is placed around the short-circuit element, it will absorb the extra heat and use it to melt the sand into a semi-liquid state. Since the silica is forced to change state, it will absorb more heat than the reaction can produce, which results in the excessive energy being controlled without damaging the fuse or the hardware and enclosures that are used to mount the fuse.

Types of Fuses