What this contactor is and where it fits
The Siemens SIRIUS 3RT1044-1AV04 is a size S3 power contactor for switching motor loads in control panels. It mounts via screw or snap-on onto 35 mm or 75 mm standard DIN rail, with a width of 70 mm and depth of 188 mm — fits a standard 8-module-wide panel cutout.
Key ratings and what they mean for your motor circuit
Rated 37 kW at 500 V and 18.6 kW at 690 V, this contactor handles typical three-phase induction motors in the 30–40 kW range on a 400 V supply. The AC-2 rating at 400 V is 30 kW — that's the slip-ring motor duty class, where the contactor makes and breaks at full load. The AC-4 rating at 400 V is 55 A, covering reversing and inching applications with high electrical wear.
Termination and environmental limits
Main current circuit uses screw-type terminals. Solid wire: 2x (0.5... 1.5 mm²), 2x (0.75... 2.5 mm²), max. 2x (0.75... 4 mm²). Stranded: 2x (10... 50 mm²). Operating temperature range -25 to +60 °C, storage -55 to +80 °C. IP20 on the front with the cover or box terminal fitted — fine for a clean panel, but not for washdown areas.