Basic Structure Of High Voltage Fuse
May 18, 2022
The fuse is mainly composed of a metal fused part (also called a melt), a current-carrying part (contact) that supports the melt, and a shell. Some fuses are also equipped with special arc extinguishing substances, such as gas-producing fiber tubes, quartz sand, etc., which are used to extinguish the arc formed when the fuse is blown.
The melt is the main component of the fuse. The melt material is required to have a low melting point, good electrical conductivity, not easy to oxidize and easy to process. Metal materials such as lead, lead-tin alloy, zinc, copper, and silver are generally used.
The melting points of lead, lead-tin alloy and zinc are relatively low, 320°c, 200°c and 420°c respectively, but the electrical conductivity is poor, so the cross-section of the fuse parts made of these materials is quite large, and the metal vapor generated when the fuse is broken Too much is not good for arc extinguishing. Therefore, it is only used in low-voltage electrical appliances of 500v and below.
Copper and silver have good electrical conductivity, but their melting points are 1080°C and 960°C, respectively. The "metallurgical effect" can be used to reduce the melting point, that is, solder balls of lead or tin on the refractory fusion parts. When the temperature When the melting point of lead or tin is reached, the refractory metal and the molten lead or tin form an alloy with high resistance and low melting point. As a result, the fused part is first fused at the small ball, and then the arc melts all the fused parts.
