Fuse refers to an electrical appliance that fuses the fuse with the heat generated by itself and disconnects the circuit when the current exceeds the specified value. The fuse is based on the fact that after the current exceeds the specified value for a period of time, the heat generated by itself melts the melt, thereby disconnecting the circuit; a current protector made by using this principle. Fuses are widely used in high and low voltage power distribution systems and control systems, as well as electrical equipment. As short circuit and overcurrent protectors, fuses are one of the most commonly used protection devices.

Common types

Plug-in fuse: It is often used at the end of the line with a voltage level of 380V and below, as a short-circuit protection for distribution branch lines or electrical equipment.

Spiral fuse: There is a fuse indicator on the upper end cover of the fuse. Once the fuse is blown, the indicator pops up immediately and can be observed through the glass hole on the porcelain cap. It is often used in the electrical control equipment of machine tools. Screw-in fuse. The breaking current is large, and it can be used for short-circuit protection in circuits with a voltage level of 500V and below and a current level of 200A.

Enclosed fuses: Enclosed fuses are divided into filler fuses and non-filler fuses, as shown in Figure 3 and Figure 4. Filler fuses generally use square porcelain tubes, which are filled with quartz sand and melt, and have strong breaking capacity. They are used in circuits with voltage levels below 500V and current levels below 1KA. The non-filler sealed fuse puts the melt into a closed cylinder, and the breaking capacity is slightly smaller. It is used in power grids or power distribution equipment below 500V and 600A.

Fast fuses: Fast fuses are mainly used for short-circuit protection of semiconductor rectifier components or rectifier devices. Due to the low overload capacity of semiconductor components. It can only withstand a large overload current in a very short time, so short-circuit protection is required to have the ability to fuse quickly. The structure of the fast fuse is basically the same as that of the stuffed closed fuse, but the material and shape of the melt are different. It is a variable cross-section melt with a V-shaped deep groove punched from a silver sheet.

Self-resetting fuses: Sodium metal is used as the melt, which has high conductivity at room temperature. When a short-circuit fault occurs in the circuit, the short-circuit current generates high temperature to rapidly vaporize the sodium, and the gaseous sodium presents a high-resistance state, thereby limiting the short-circuit current. When the short-circuit current disappears, the temperature drops, and the sodium metal recovers its original good electrical conductivity. Resettable fuses can only limit the short-circuit current and cannot actually break the circuit. The advantage is that there is no need to replace the melt and it can be used repeatedly.