Structure of fast fuse: The fuse consists of magnetic shell, conductive plate, melt, quartz sand, arc extinguishing agent and indicator. The material of the melt is pure silver, the shape of the melt is rectangular sheet, and it has a round hole and narrow neck [1]< br> Arc extinguishing principle of fast fuse The melt of fast fuse is made of pure silver. Because of the low resistivity, good ductility and good chemical stability of pure silver, the melt of fast fuse can be made into thin sheet with round hole and narrow neck structure. When a short circuit fault occurs, the current density at the narrow neck is high, so the narrow neck is fused first and divided into many small sections by quartz sand. In this way, the arc formed by melt fusing is divided into many small sections by quartz sand, the arc current is small, the distribution space is small, and it is easy to be absorbed by arc extinguishing agent. Because the quartz sand is insulated, an insulator is formed immediately after the arc is extinguished, which breaks the circuit Characteristics of fast fuse Inverse time current protection characteristics. The fuse has the characteristics of anti time delay, that is, when the overload current is small, the fusing time is long; When the overload current is large, the fusing time is short. Therefore, in a certain range of overload current and overload time, the fuse will not fuse and can be used continuously. The fuse has various fusing characteristic curves, which can be applied to the needs of different types of protection objects< br> Current limiting characteristics Because the melt of the fast fuse is a rectangular sheet with a series of round holes and narrow necks, and is filled with quartz sand arc extinguishing medium. The cross-sectional area of the narrow neck of the circular hole is small and the heat capacity is small. When the short-circuit fault occurs, the fault current is fused before it reaches the expected short-circuit current, and the arc is divided into many small sections by quartz sand. This not only limits the increase of short circuit current, but also accelerates the extinction of arc< br> Strong breaking ability < br > was found When the short circuit fault occurs, the narrow neck of the round hole is fused first, and the arc is divided into many small sections by quartz sand, and the arc is extinguished quickly. As the quartz sand is insulated, after the arc is extinguished, the fuse immediately becomes an insulator, breaking the circuit. Therefore, the breaking capacity of fast fuse is strong, which can be as high as 50kA< br> The impact energy of load equipment is small < br > 0 In case of short circuit fault, the impact energy of load equipment is w = i2rt, where I - short circuit current; R - resistance of the circuit; T - the time from the occurrence of short circuit fault to the cut-off of the circuit. The quick fuse has a short breaking time and has a good current limiting effect, so the impact energy of load equipment is small.