Mersen - Fuse The Smart Choice For Electrical Protection
- Published: Tuesday, 21 March 2017 13:22
The Mersen Electrical Power’s Current limitation is one of the most important features of today’s fuses. By isolating a faulted circuit before the fault current has sufficient time to reach its maximum value, a current limiting fuse can:
• Limit the total energy delivered to arcing faults
• Limit thermal and mechanical stresses created in the system by the fault currents
• Reduce the magnitude and duration of the system voltage drop caused by fault currents
• Minimize downtime, since current limiting fuses can be precisely and easily coordinated even under short circuit conditions.
If the arc fault current is large enough for a current limiting fuse to be in its current limiting range, the fuse will dramatically reduce the electrical energy delivered to the arc.
The short circuit element of a fuse is made of strips of copper or silver with regions of reduced cross sectional area called notches. There may be several strips in parallel, depending on the ampere rating of the fuse. The short circuit elements are enclosed in an insulating body filled with pure quartz sand. At each end are terminals such as blades or ferrules to permit installation into fuse-folders or connection to bus bars. During normal load operation, the fuse elements carry the currents without melting.
Current limiting operation begins at the initiation of a short circuit. As the short circuit current starts to rise, the elements melt very quickly at the notches and a number of small electric arcs are produced in the notch zones. The increasing impedance of the arcs causes the fault current to be rapidly reduced to zero and the arcs are extinguished.