Siemens SIRIUS 3RT1044-1AL28-0PA4 — Power Contactor, Size S3
It is rated for 37 kW at 500 V in AC-3 duty, meaning it handles the inrush and breaking of squirrel-cage motors up to that power level. The main current circuit uses screw-type terminals, accepting solid conductors from 0.5 mm² up to 4 mm² (two per clamp) and stranded conductors from 10 mm² to 50 mm² (two per clamp). This terminal range covers typical motor feeder cables from control to power distribution.
The 37 kW rating at 500 V is the AC-3 motor switching capacity — the spec that determines whether this contactor handles your motor's locked-rotor current and break current. At 690 V the same contactor is rated for 18.6 kW, reflecting the higher voltage stress on the arc chamber. IP20 protection on the front with the cover or box terminal installed means the contactor is finger-safe in the panel but not protected against water ingress. The terminal area itself is rated IP00, so the panel enclosure provides the environmental seal.
Dimensions are 146 mm height, 70 mm width, and 139 mm depth. The 70 mm width means it occupies roughly four 17.5 mm DIN-rail module spaces. Snap-on mounting onto 35 mm or 75 mm rail is standard, and the screw fixing option provides a positive lock in high-vibration environments. The contactor is rated for both 50 Hz and 60 Hz operation, with the operating range spanning 0.8 to 1.1 times rated voltage at 50 Hz and 0.85 to 1.1 at 60 Hz. This covers global line variations without adjustment.