Drop-out Fuses: The Overlooked Fuse Resistance And Its Function
In the operation and maintenance of high-voltage power distribution equipment, the fuse inside the drop out expulsion fuse has a certain resistance. This physical characteristic is not a design flaw, but rather the basis for the drop out fuse 22kv to achieve reliable protection functions. Many operational failures often stem from neglecting this parameter.
Thermal Effect: The Functional Relationship Between Resistance and Time
The resistance value of the fuse determines its thermal effect under normal operating current. When current flows through the fuse, the heat generated by the resistance is proportional to the square of the current and time. This thermal accumulation process is the core of the drop out fuse 33kv's inverse time protection characteristics. The fuse material is usually high-purity silver or silver-copper alloy, and its precise cross-sectional area is measured by laser to ensure the melting characteristics required for the current-limiting fuse.
When a fault occurs, the short-circuit current causes the fuse to rapidly heat up to its melting point. The instant the fuse melts, an electric arc is generated. The high temperature of the arc causes a large amount of gas to decompose on the inner wall of the arc-extinguishing tube, causing a sharp increase in pressure inside the tube. The high-speed ejection of gas extinguishes the arc. The resistance value of the fuse directly affects the melting time during this process, determining the selectivity of the protection action.
Mechanical Tension: The Indirect Structural Role of Resistance
The fuse in a drop out fuse cut out fuse has a dual function. The moving contacts at both ends of the fuse tube are secured by the fuse itself. Pushing the upper moving contact into the "duckbill" protrusion secures the fuse tube within the "duckbill." The fuse's resistive characteristics and mechanical strength are designed to be balanced. The fuse must withstand approximately 24.5 N of tension to maintain a closed state. Materials with excessively high resistivity cannot simultaneously meet the requirements for current carrying capacity and mechanical strength. Therefore, standard fuses use a silver-copper alloy with excellent conductivity, maintaining low resistance while possessing a tensile strength of over 147 N.
After the fuse melts, the tension disappears, releasing the locking mechanism. The fuse tube, under the influence of the upper stationary contact's elasticity and its own weight, flips and falls around the lower axis, creating a significant breaking distance. The reliability of this mechanical action also depends on the melting process caused by the fuse's resistive thermal effect.
