Why Do The Internal Materials Of A Fuse Decompose At High Temperatures?

In the structure of filler drop out fuse, a steel paper sleeve or similar fibrous material surrounds the fuse wire inside the fusible tube. Heat originates from the fuse wire itself heating up when the current exceeds the design value, causing a rapid rise in local temperature that exceeds the thermal stability limit of the internal material. The decomposition of this type of steel paper composite material at high temperatures is part of the design and not accidental. The decomposition of the material releases gases, which create an atmosphere within the narrow fusible tube space that helps suppress the persistence of the electric arc, prompting it to extinguish quickly.

During the melting process, the electric arc forms because the current seeks a new conductive path at the moment the fuse wire melts, typically generating high-temperature ionized gas near the break. The gases and decomposition products generated by the decomposition of the built-in steel paper sleeve under thermal effects act as an arc-suppressing medium in the arc region, reducing arc energy and altering the gas dielectric properties, helping to suppress and elongate the arc and reduce the possibility of re-energization.