Fuse And Short-circuit Capacity Exceeding Limits Cause Contact Erosion.

When the drop out fuse rating in the system design fails to account for the actual short-circuit current level, and the current surges beyond the fuse's rated breaking capacity, the contact points in the circuit are highly susceptible to ablation or melting due to excessive current and intense arcing.

The molten metal inside the fuse melts rapidly upon the occurrence of a short circuit, thus disconnecting the circuit. If the short-circuit capacity (i.e., the fault current intensity) exceeds the fuse's designed breaking capacity, the fuse may fail to disconnect the current in time, causing current to continue flowing through the contact point connected to the busbar. The high current and arc heat at this point will rapidly heat the surface of the metal contact, causing oxidation or instantaneous vaporization of the metal, resulting in severe ablation.