The working principle of the drop fuse can be divided into three stages: normal operation, failure and fuse:

During normal operation: the moving contacts at both ends of the fuse tube rely on the tension of the fuse (melt) to push the upper moving contact into the protruding part of the "duckbill" and closely contact the upper static contact to form a closed state. At this time, the current can flow normally through the fuse tube.

When a fault occurs: When a short-circuit fault occurs in the circuit, an excessive current will quickly blow the fuse and produce an arc. The steel paper tube lined by the fuse tube will produce a large amount of gas under the action of the arc. These gases will form a high pressure in the fuse tube and spray out to the lower end to blow out the arc.

After fusing: after the fuse is fused, the upper and lower moving contacts of the fuse tube lose the tension of the fuse. Under the action of its own gravity and the spring pieces of the upper and lower static contacts, the fuse tube drops rapidly, causing the circuit to be disconnected and the faulty section of the circuit or equipment to be cut off.