S&C Electric Company 121100-R3 Refill Unit Power Fuse Type

S&C Electric Company 121100-R3 SM-4 Refill Unit is a 7.2 kV nominal, 65E‑rated refill cartridge designed for use in SM‑4 power fuse holders (and compatible with SML‑4 and SME‑4Z configurations) to be replaced after a fault‑clearing operation. It features a pull‑ring, porcelain jacket, rain shield, lifting eye, and a hexagonal clamping nut to secure it in the holder, plus internal components such as a stainless‑steel spring and copper load cable that provide rapid arc elongation and carry fault current through the unit. This Coordinating Speed refill unit is intended for 7.2 kV distribution schemes, enabling quick re‑energization while maintaining coordination with adjacent protective devices; replace only after fault clearance and in accordance with the holder’s specifications to preserve proper ratings and compatibility.