The GS1SD4 is a TeSys GS fuse switch disconnector body — a 4-pole, DIN-rail-mounted unit rated for 630 A conventional free air thermal current at 40 °C. That 630 A figure is your headline: it tells you the body can carry that much continuous current without exceeding its temperature rise limits, as long as the ambient stays under 40 °C. The real work rating depends on your load type and voltage — for AC-23B motor switching at 400 V, it's still good for 630 A, and at 690 V AC-23A it's rated 315 A. So for a heavy motor or resistive bank on a 400 V line, this body has the copper to handle it. Making capacity is 6300 A at the same voltage, meaning it can close onto a fault without welding contacts. Both numbers come from the IEC 60947-3 standard, which governs switch-disconnector performance. For a 400 V panel with a service entrance rated higher than 5 kA, you'll want to check the upstream fuse coordination to keep this body within its interrupt rating.
The 4-pole configuration covers three-phase plus neutral or a second switched pole, common in distribution and motor feeder circuits. The operating handle is on the right side, which matters for panel layout if you're stacking multiple units side by side — keep clearance for the handle swing. Connections are via power circuit bars or screw terminals accepting up to 2 x 300 mm² flexible cable, torqued to 44 N·m. That's a serious lug, sized for the 630 A rating. The fuse cover is rated for 850 °C glow-wire test and the body for 960 °C, per IEC 60695-2-1. That fire resistance means it won't propagate a flame if a fuse blows hard.
The GS1SD4 is designed and tested to IEC 60269-1, IEC 60269-2 (fuse standards), and IEC 60947-3 (switch-disconnector standard). Rated insulation voltage is 1000 V AC, and impulse withstand voltage is 12 kV. That 12 kV figure is the surge it can take without flashover — important for installations with lightning risk or switching transients. Rated short-circuit making capacity with gG fuse protection is 100 kA at 400 V, but that's limited by the fuse rating of 630 A — the fuse clears the fault, not the switch body, so the body just has to survive the let-through.