Heat Accumulation And Temperature Change Process Of Fuse

When a large current flows through a circuit, the temperature of a metallic conductor rises due to the thermal effect of the current. The drop out fuse utilizes this physical property to achieve circuit protection by melting the internal molten metal.

When current flows through the molten metal, it generates heat due to resistance. The rate of heat generation and dissipation together determine the temperature rise of the metal surface. When the product of current and resistance (i.e., heat power) exceeds the heat dissipation power, the metal temperature continues to rise. According to Newton's law of thermal expansion, the rate of heat dissipation is related to the surface temperature difference, the heat transfer coefficient, and the heat dissipation area. Once the metal temperature rises above its melting point, the molten metal begins to melt.