Its headline rating is 37 kW at AC-2 duty class on a 400 V supply — that's the current it can make and break under the moderate overloads typical of slip-ring motors or wound-rotor drives, where the inrush is less severe than AC-3 but still requires a contactor rated for the duty cycle. The AC-4 rating of 66 A at 400 V covers the plugging and inching operations that generate the highest arc energy; if your application includes frequent reversing or jogging, the AC-4 figure is the one that governs contact life, not the AC-2 number.
The size S3 footprint (146 mm high, 70 mm wide, 139 mm deep) fits standard gland-plate layouts; side-by-side mounting is permitted, so you can gang multiple contactors without derating for heat buildup as long as ambient stays within the -25 to +60 °C operating range. Screw-type terminals on the main circuit accept 2x (10 to 50 mm²) stranded or 2x (0.25 to 2.5 mm²) solid, which covers most motor feeder cables up to 50 mm² without needing lug adapters.
The front carries IP20 protection with the cover and box terminal fitted; the terminal area itself is IP00, so the panel enclosure must provide the overall ingress protection. Mechanical life is rated at 10,000,000 operating cycles typical, which for a contactor on a conveyor or pump running at 1,000 cycles per hour (AC-3 maximum) translates to roughly 10,000 hours of switching before mechanical wear becomes a factor — the electrical life under load will be shorter and depends on the actual duty class.