The Siemens 3RT1045-3AB00 is a SIRIUS S3 power contactor rated for 37 kW in AC-2 duty at 400 V and 66 A in AC-4 duty — the AC-2 figure is the one that governs motor switching for slip-ring or wound-rotor applications where the load current stays near the contact rating during acceleration. The AC-4 rating (66 A) covers reversing or inching duty where the contactor opens under full motor current, so the 66 A ceiling is the hard limit for plugging or jogging cycles.
Snap-on mounting onto 35 mm or 75 mm standard DIN rail, with screw fixing as an option. Screw-type terminals on the main circuit accept 2x (10–50 mm²) stranded or 2x (0.25–2.5 mm²) solid — the larger stranded range is what you'll use for the power legs; the solid range is for control wiring or auxiliary connections.
Environmental and protection
IP20 on the front with the cover or box terminal fitted; the terminal body itself is IP00, so the panel enclosure must provide the overall ingress protection.