SMD^® Power Fuses, Outdoor Distribution

Fault Interruption

Fast, positive fault interruption is achieved in SMU Fuse Units through high-speed elongation of the arc in the solid-material-lined bore, and by the efficient deionizing action of gases generated through thermal reaction of the solid material due to the heat of the confined arc. The resultant high rate of dielectric recovery voltage more than matches the transient recovery voltage severity of the circuit.

Here’s How it Works

1. Overcurrent melts the silver fusible element. The strain wire severs, initiating arcing.
2. Released force of drive spring accelerates arcing rod upward, causing rapid elongation of the arc in the solid-material-lined bore. Under maximum fault conditions, heat from confined arc causes solid material in the large-diameter lower section of the arc-extinguishing chamber to undergo thermal reaction, generating turbulent gases and effectively enlarging the bore diameter so that the arc energy is released with a mild exhaust. Under low-to-moderate fault conditions, arc is extinguished in the small-diameter upper section of the arc-extinguishing chamber, where deionizing gases are effectively concentrated for efficient arc extinction.
3. Continued upward travel of the arcing rod after arc extinction causes actuating pin to penetrate the upper seal, initiating positive dropout of the fuse unit.