UL/CSA Current Limiting Fuses From Mersen

Mersen Amp-Trap®The Mersen Electrical Power’s offering of fuse and fusegear covers all the international standards IEC, with DIN, BS88 and French and also UL/CSA.

Mersen’s comprehensive UL/CSA power fuse offering covers a complete range of applications and a complete range of circuit-protection needs.

The most famous lines are the Tri-Onic® time-delay fuses, the original Amp-Trap® high current-limiting capacity power fuses and the HSJ High-Speed Class J fuses.

mersen hsjCurrent limiting fuses can reduce both the magnitude and duration of a fault current. A UL Listed, current limiting fuse must clear a short circuit current in less than one half cycle in its current limiting range. In this condition the fuse will melt in the first quarter cycle and prevent the fault current from reaching the first peak of the asymmetrical waveform, significantly limiting the total electrical energy delivered to the fault. This energy limitation enables class J, RK1, T and L UL/CSA fuses to reduce incident heat energy from an arc flash to very low levels. 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.


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