The element in a fuse is usually a wire or thin metal strip mounted between two terminals. In a cartridge fuse, it is enclosed in a glass or ceramic cylinder with a contact at each end, or in a small metallic can. Old-style, large, high-amperage fuses may be packaged in a paper or cardboard tube.The traditional glass cartridge allows a visual inspection to confirm that the fuse has blown.A fuse responds only to current, not to voltage. When choosing a fuse that will be reliable in conditions of steady current consumption, a safe rule is to figure the maximum amperage when all components are functioning and add 50%.
However, if current surges or spikes are likely, their duration will be relevant. If “I” is the current surge in amps and “t” is its duration in seconds, the surge sensitivity of a fuse — given by the formula: