Electronics

Main classification of fuses

Fuses can be divided into high-voltage fuses and low-voltage fuses according to the service voltage. According to the protection object, it can be divided into fuses for protecting transformers and general electrical equipment, fuses for protecting voltage transformers, fuses for protecting power capacitors, fuses for protecting semiconductor components, fuses for protecting motors and fuses for protecting household appliances. According to the structure, it can be divided into open, semi closed, tubular and jet fuses.

The open fuse has simple structure, the melt is completely exposed to the air, supported by porcelain column and no support. It is suitable for low-voltage outdoor use. When breaking the current, it produces large sound and light in the atmosphere.

The melt of the semi enclosed fuse is installed on the porcelain frame and inserted into the porcelain box with metal sockets at both ends, which is suitable for low-voltage indoor use. When breaking the current, the generated sound and light are blocked by the porcelain box.

The melt of the tubular fuse is installed in the fuse body. Then it is inserted into the support or directly connected to the circuit. The fuse link is a completely sealed insulating tube with metal caps on both ends or contact knives. If the insulating tube of this fuse is filled with quartz sand, it has the function of limited current during breaking current, which can greatly improve the breaking capacity, so it is also called high breaking capacity fuse. If vacuum is pumped in the tube, it is called vacuum fuse. If the tube is filled with SF6 gas, it is called SF6 fuse, which aims to improve the arc extinguishing performance. Because quartz sand, vacuum and SF6 gas have good insulation properties, this fuse is suitable for both low voltage and high voltage.

The jet fuse is to install the melt in an insulating tube made of solid gas producing material. Solid gas producing materials can be electrical anti white paperboard or plexiglass materials. When the short-circuit current passes through the melt, the melt will fuse and produce an arc. The high-temperature arc will quickly decompose the solid gas producing material and produce a large amount of high-pressure gas, so as to eject the ionized gas charged arc at both ends of the pipe, emit great sound and light, and extinguish the electric arc when the AC current crosses zero to cut off the current. The insulating tube is usually installed on an insulating support to form the whole fuse. Sometimes, the upper end of the insulating tube is made into a movable type, which is disconnected and dropped immediately after breaking the current. This kind of jet fuse is commonly known as drop fuse. It is generally suitable for outdoor occasions with voltage higher than 6kV.

In addition, the fuse can also be divided into general purpose fuse, backup fuse and full range fuse according to the breaking current range. The breaking current range of general-purpose fuse refers to the range from the overload current is 1.6 ~ 2 times greater than the rated current to the maximum breaking current. This fuse is mainly used to protect power transformers and general electrical equipment. The breaking current range of backup fuse refers to the range from the overload current 4 ~ 7 times higher than the rated current to the maximum breaking current. This kind of fuse is often used in series with the contactor. When the overload current is less than 4 ~ 7 times of the rated current, the contactor realizes the breaking protection. It is mainly used to protect the motor.

With the needs of industrial development, special fuses suitable for various requirements are also manufactured, such as electronic fuses, thermal fuses and self restoring fuses.

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