The Siemens SIRIUS 3RT1317-1AH00 is a size S00 power contactor with four normally-open main contacts, rated for 5.5 kW at AC-2 duty on 400 V. AC-2 is the standard for slip-ring motor starting and switching — the contactor handles the inrush and the higher switching frequency of wound-rotor motors without excessive contact wear. The 4-pole NO arrangement means it makes all four poles on pickup; there are no normally-closed main contacts on this variant, so it is a straight make-only device for motor or resistive loads where you need to switch all phases plus the neutral. The auxiliary contact block is rated for 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V — these are the thermal current (AC-12) limits for the control circuit. For inductive DC loads, the ratings drop to 2 A at 60 V and 0.3 A at 220 V, which is typical for contactor auxiliaries and reflects the arc-extinction challenge on DC. If you are switching a DC solenoid or brake coil, stay within those limits or add a free-wheel diode. If this contactor sits in a steel-mill pulpit with HVAC, it is fine; if it is mounted on the mill floor near the rolls, you need to check the enclosure ambient.
The S00 footprint is 45 mm wide, 57.5 mm tall, and 72 mm deep — compact enough for dense panel layouts. Screw-type terminals on the main circuit accept 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or up to 2x (0.75 to 4 mm²) — or 1x 12 AWG. The control circuit uses the same terminal range. For Type 1 coordination, the maximum fuse is 35 A gL/gG; for Type 2 coordination (no welding of contacts on fault), it is 20 A gL/gG. That is the short-circuit protection the upstream breaker or fuse must provide to keep the contactor repairable after a fault.