Siemens SIRIUS 3RT1044-1AL28-0PA4 — Power Contactor, Size S3
The Siemens 3RT1044-1AL28-0PA4 is a SIRIUS power contactor in the size S3 frame, designed for switching motor loads in industrial control panels. 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 contactor mounts via screw or snap-on onto 35 mm and 75 mm standard mounting rails, so it integrates directly into a DIN-rail panel layout. 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.
Key Ratings and What They Mean for Fit
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. For resistive or lightly inductive loads (AC-1), the switching rate can reach 1000 operations per hour, while heavy AC-4 duty (plugging, inching) is limited to 300 operations per hour. The contactor is rated for a pollution degree of 3, meaning it is suitable for industrial environments with conductive pollution or dry non-conductive pollution that becomes conductive due to condensation. The operating temperature range is -25 °C to +60 °C, with storage from -55 °C to +80 °C. Side-by-side mounting is permitted without derating, which saves panel width when grouping multiple contactors. 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.
Panel Integration Notes
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.