Common types of fuses and interstage fit

Common types of fuses

◆ Plug-in fuse: this kind of equipment is generally used in line end positions of 380V and below voltage classes, mainly to play a corresponding protection role in case of short-circuit fault of distribution branch or electrical equipment.

◆ Screw fuse: The feature of this type of fuse is that the upper end cover is provided with an indicator to show the fuse status. If the melt performs the fuse action, the indicator will pop up immediately. At the same time, it can be clearly observed through the glass hole on the porcelain cap. Screw fuses are often used in the electrical control equipment of machine tools, and have a large performance of breaking current. Suitable for circuits with voltage level up to 500V and current level up to 200A, fuses can play the role of short circuit protection.

◆ Enclosed fuse: it can be divided into two types, including packing and no packing, while packing fuse is usually made of square porcelain tube, with quartz sand and solution inside, which has strong breaking ability. This kind of equipment can be used in the circuit with voltage class below 500V and current class below 1kA. Packless fuses adopt the closed design to load the solution into the closed cylinder, but its breaking capacity will be slightly smaller than the previous material, mainly suitable for power network or distribution equipment with the current level below 500V and below 600A.

◆ Fast fuse: it can be said that this type of fuse is the most common and commonly used, generally used in semiconductor rectifier elements or rectifier devices to protect the short circuit. Because the overload capacity of semiconductor components is relatively weak and low, it can only bear a large overload current in a very short time. Therefore, short circuit protection in this scenario requires the ability of rapid fusing. The structure of the fast fuse is basically the same as that of the packed and closed fuse mentioned above, but the internal melt and shape are different to some extent. It is a variable cross section melt with v-shaped deep slot made of silver sheet.

Since after fuse: this is a kind of using sodium metal as melt fuse protection device, under the normal temperature with high conductivity, short-circuit fault occurs when the protected circuit, short circuit current generated by the high temperature will make the metal sodium rapid gasification, at the same time when the gasification of sodium metal presents high impedance state is restricting short circuit current will be smooth. After the fault is completely eliminated, the temperature will drop and the sodium metal in the self-recombination fuse will return to its original good electrical conductivity. The device can only limit the short-circuit current, can not really achieve the effect of circuit breaking, its characteristics is not like other fuses need to replace the melt, but can be reused.

Fuse stage fit

Above in order to be able to prevent avoid fusing and expanding the scope of the accident, and so on, at a lower level (i.e., the power supply of the main line and branch line) on a line between the fuse must want to have a good cooperate, at the time of selection should be the higher of the power supply line fuse melts rated current than the lower (supply side) on the big rebound in the 1 to 2.

The above is the common types of fuses and the coordination between stages, I hope to help you.