The melt of high breaking capacity fuses is usually made of copper, but also silver. When the rated current is small, the melt is often made into a filament; when the rated current is large, it is made into a variable cross-section. Since both copper and silver are high-melting-point metal materials, in order to reliably break the current under overload current, low-melting-point metals, such as tin or cadmium alloys, are often welded at a certain interval of the melt to reduce the melting temperature. This effect is also called metallurgical effect (M effect). The fast fuse in the device for protecting semiconductor components is basically the same in structure as the general high breaking capacity fuse, but it does not use metallurgical effect, and the melt is made of silver. High current density to achieve fast breaking effect.
The melt is packed in a porcelain tube (or glass fiber tube) filled with quartz sand, and the fuse uses quartz sand as an arc-extinguishing medium. The particle size of quartz sand has a great influence on the arc extinguishing performance, and the particle diameter is generally selected in the range of 0.2-0.3mm. When the overload current or short-circuit current passes through the fuse, the melt fuses and an arc is generated in the tube. Because the quartz sand has a strong cooling effect and deionization effect on the arc, the arc is quickly extinguished. When breaking a large short-circuit current, the arc can usually be extinguished before the short-circuit current reaches its maximum value. In the whole process of breaking the current, there is no sound and light phenomenon, and no ionized gas is ejected, and the breaking capacity is high. It is widely used in indoor high-voltage and low-voltage power distribution devices, and is also used in household appliances. In addition, fast fuses are also made for the protection of semiconductor device devices.