Fuses are electrical components that protect electrical circuits, components, assemblies or devices against overloads and short circuits. They are located before the power supply or on the components to be protected.
The fuse is a thin fusible wire defined to melt at elevated current. The fusible wire is contained in a thin glass tube and is soldered to the terminating metal sleeves on both sides. The glass tube can be filled with air or fine sand and provides protection against the glowing fuse wire.
The fuse value is determined by the wire thickness, the melting time characteristic by the material and the structure. Melting characteristics are divided into fast-blow (F), super-fast-blow ( FF), medium-blow (M), slow-blow(T) and super-blow(TT). The rated current range for fuses is between 0.032 A and 6.3 A.
Other fuse designs
In addition to the fine-wire fuse, which is inserted into a fuse holder, there are also disposable SMD fuses in solid-body fuse, also known as chip fuse, and wire-in-air fuse designs. Chip fuses are used in small appliances, hard drives and other space-saving applications. They have similar melting characteristics to fine-wire fuses and respond superfast (FF), fast-blow (F), or even slow-blow (T). Chip fuses are available in many rated current versions, for high rated voltages and for high switching currents.
Chip fuses are chip-shaped and consist of a ceramic substrate on which a structured platinum layer, the fusible element, is applied. On top of this is a cover layer. The contacts form round contacts, which are located on the transverse sides and hold the chip fuse together.
Another type of fuse to be mentioned is the electronic fuse, the e-fuse or electronic fuse. As far as household fuses are concerned, these are circuit breakers - in English: Circuit Breaker - more commonly known as automatic circuit breaker.