Working principle and application of fuse

Fuse refers to an electrical appliance that fuses the melt and breaks the circuit with its own heat when the current exceeds the specified value. The fuse melts the melt with its own heat after the current exceeds the specified value for a period of time, so as to disconnect the circuit; A current protector based on this principle. Fuses are widely used in high and low voltage distribution systems, control systems and electrical equipment. As short circuit and over-current protectors, fuses are one of the widely used protective devices.

An electrical appliance that uses a metal conductor as a melt in series in a circuit. When an overload or short circuit current passes through the melt, it will fuse due to its own heating, thus breaking the circuit. The fuse has simple structure and is easy to use. It is widely used in power systems, various electrical equipment and household appliances as a protective device.

The fuse is mainly composed of three parts: melt, shell and support. The melt is the key element to control the fusing characteristics. The fusing characteristics are determined by the material, size and shape of the melt. Melt materials can be divided into low melting point and high melting point. Low melting point materials, such as lead and lead alloys, have low melting point and are easy to fuse. Because of their high resistivity, the cross section size of the melt is large, and more metal vapor is generated during fusing, so they are only applicable to fuses with low breaking capacity. High melting point materials, such as copper and silver, have high melting points and are not easy to fuse. However, due to their low resistivity, they can be made into smaller section sizes than low melting point melts, and generate less metal vapor when fusing. They are suitable for fuses with high breaking capacity. The shape of the melt can be divided into filament and ribbon. The fusing characteristics of fuses can be changed by changing the shape of variable cross-section. Fuses have different fusing characteristic curves, which can be applied to the needs of different types of protection objects.

Working principle of fuse

The working principle of fuse is a simple relationship between I2R and time. The greater the current, the shorter the fusing or open circuit time. The power consumption of the fuse is proportional to the square of the current passing through the fuse. When the power consumption is too high, the fuse is blown. This feature is also applicable to the harness protected by the fuse. If the heat generated exceeds the heat emitted, the temperature of the fuse will increase. When the temperature rises to the fuse melting point of the fuse, the fuse will fuse, that is, disconnect the circuit for protection.

Use and maintenance

The fuse in low-voltage power distribution system is a kind of electrical appliance that plays a role of safety protection. The fuse is widely used in power grid protection and electrical equipment protection. In case of short circuit fault or overload of power grid or electrical equipment, it can automatically cut off the circuit to avoid damage to electrical equipment and prevent accidents from spreading.

The fuse is composed of insulation base (or support), contact, melt, etc. The melt is the main working part of the fuse. The melt is equivalent to a special conductor in series in the circuit. When the circuit is short circuited or overloaded, the current is too large, and the melt melts due to overheating, thus cutting off the circuit. The melt is often made into filament, grid or sheet. Melt materials have the characteristics of low relative melting point, stable characteristics and easy fusing. Lead tin alloy, silver plated copper sheet, zinc, silver and other metals are generally used. In order to extinguish the arc safely and effectively, the melt is generally installed in the fuse housing and measures are taken to extinguish the arc quickly.

Fuses are widely used in low-voltage systems because of their simple structure, convenient use and low price.