We know: the action principle of tube fuse is over current makes the melt on the heat balance is broken, the melt temperatures to rise to the melting point of metal materials, from solid to liquid, in the middle of the melt due to dangling the surface tension of the metal material in the tube and the liquid part of the gravity makes the melt to the ends of distance and hung down, voltage caused by arcing and makes the melt temperature continues to rise, further arcing and further distance, until the circuit is completely cut off.

A fuse of the corresponding patch type, its action principle is the same, but because of the difference of structure state, metallic melts all around was the matrix of polymer or ceramics materials tightly around the stick, even have shrinkage on both ends of the molten metal also are unable to, can only rely on diffusion penetration or be absorbed into the surrounding material, if in the process of the over current disappeared (such as instantaneous pulse phenomenon), and is still in the process of the spread or absorption process, at this time can cause resistance to become big and the phenomenon of sample's not completely melt.

Take a look at the consequences of this phenomenon: because the overcurrent has disappeared, and no adverse effects on the circuit, although at this time of the fuse not be fuse, but the capacity of the melt has waned, the over current again will be faster by fusing, ensure the protection of circuit; If the second is still instant pulse current, can cause resistance to become big and still didn't have a perfectly fusing, the capacity of the melt is also weakened again; All told, resistance larger patch fuses perfectly fusing phenomenon does not affect it for circuit protection function, as long as overcurrent last a long time, it will be perfectly fusing. On the contrary if survived over current without any change, may be the fuse protection function has a problem.

Then compare tube fuse, slow type fuse melts by two or more composite metal material, under the over current also has a process of diffusion penetration between different materials, so it will has the ability of resistance to pulse, also have the opportunity to produce resistance larger phenomenon.