What this contactor is and what it does
The Siemens 3RT1317-1BW40 is a SIRIUS S00 power contactor with four normally open main contacts and a 24 VDC coil. It switches motor loads up to 5.5 kW at 400 V in AC-2 duty — that's the rating that matters for slip-ring or wound-rotor motor starting, where the contactor makes and breaks the load current. The DC coil draws 3.3 W to close and holds at the same power, so there's no holding-power drop to account for in the control transformer sizing.
Mounting and panel fit
Snaps onto 35 mm DIN rail per DIN EN 50022 — no tools needed for the rail, but the screw-type terminals on the main circuit will need a screwdriver. The 45 mm width and 57.5 mm height mean it takes up one standard 45 mm module slot on the rail. Depth is 72 mm, so watch the gland-plate clearance if you're mounting it near the back of a shallow enclosure. Side-by-side mounting is allowed with a 6 mm gap at the side — no derating required for adjacent units as long as that spacing is kept.
Switching capacity and coordination
The contactor's switching current depends on the voltage you're working with. At 24 V it handles 10 A; at 60 V it's 2 A; at 110 V it's 1 A; at 220 V it's 0.3 A; at 230 V it's 6 A; at 400 V it's 3 A. For motor starting in AC-2, the rated power is 5.5 kW at 400 V. The contactor is rated for pollution degree 3, so it's suitable for industrial environments where conductive dust or condensation might be present. Type 1 coordination calls for a 35 A gL/gG fuse; Type 2 coordination needs a 20 A gL/gG fuse. That's the fuse size to spec if you want the contactor to survive a short circuit without replacement.