What It Is and What It Does
The Siemens SIRIUS 3RT1044-1BB44-3MA0 is a power contactor in the S3 frame size, designed for switching motor loads in industrial control panels. Its AC-4 rating at 55 A at 400 V means it handles the severe inrush and breaking duty of reversing or plugging applications — the kind of service that cycles a motor from forward to stop to reverse without a coasting delay. For AC-2 duty (starting and stopping slip-ring motors), it is rated at 30 kW at 400 V. The AC-3 rating supports 37 kW at 500 V, covering the bulk of standard squirrel-cage motor starts. The contactor mounts via screw or snap-on onto 35 mm or 75 mm standard DIN rail, fitting into a 70 mm wide slot.
Terminal and Environmental Ratings
The main current circuit uses screw-type terminals, accepting solid conductors up to 2x (0.5... 1.5 mm²) or 2x (0.75... 2.5 mm²), and stranded conductors up to 2x (10... 50 mm²). The contactor is rated IP20 on the front with a cover or box terminal; the terminal body itself is IP00, so the panel enclosure provides the overall ingress protection. Operating temperature range is -25 to +60 °C, storage from -55 to +80 °C. Pollution degree 3 means it tolerates conductive dust and occasional condensation — typical for industrial enclosures not fully sealed.
Coil and Auxiliary Contact Ratings
The coil is rated at 24 V DC, drawing 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, and 0.3 A at 220 V. For DC switching, the arcing time is 10 to 15 ms, and the dropout time is 14 to 20 ms. The contactor's mechanical life is typically 10,000,000 operations.