Thermal Runaway Caused By Narrowing Of The Conductive Path Of The Fuse

When the cross-sectional area of ​​a conductive path decreases significantly, the resistance increases dramatically inversely. According to Joule's law, the heat generated by current flowing through a conductor is directly proportional to its resistance. The resistance in the narrowed region increases sharply, causing the heat generation at that location to increase exponentially, and the temperature rapidly exceeds the material's safe operating range.

The formation of this localized high-temperature zone triggers a phase transition process in the material. After reaching its melting point, the fuse element begins to soften, and the metal lattice structure gradually disintegrates. The continued rise in temperature causes the molten element to transform from a solid to a liquid state, eventually melting completely under high temperature, achieving physical isolation of the circuit. Throughout this process, the energy release rate and temperature gradient distribution directly affect the breaking characteristics of the drop out fuse.