Siemens SIRIUS 3RT1044-1BF44 — Power Contactor, Size S3
The Siemens SIRIUS 3RT1044-1BF44 is a size S3 power contactor designed for motor switching and general load management in industrial control panels. It is rated for AC-4 duty at 55 A at 400 V, which means it handles the toughest motor switching — plugging, inching, and reversing — where the contactor must break locked-rotor current. The 110 V coil keeps it compatible with common control transformer secondaries across North American and European panels.
Mounting and Integration
Mounts via screw fixing or snaps onto 35 mm or 75 mm DIN rail. The S3 frame — 70 mm wide, 146 mm tall, 201 mm deep — fits standard panel layouts with room for side-by-side mounting without derating. Screw-type terminals on the main circuit accept stranded conductors up to 2x 50 mm² and solid up to 2x 4 mm². Operating temperature range of -25 to +60 °C suits most indoor industrial environments.
Switching Performance and Ratings
Beyond the AC-4 rating, the contactor handles AC-2 duty at 30 kW at 400 V for slip-ring motors, and AC-1 resistive loads at up to 1,000 operations per hour. The DC switching capability is modest — 10 A at 24 V, 1 A at 110 V, 0.3 A at 220 V — so for DC loads, verify the rating against your circuit. Arcing time is 10–15 ms, and the mechanical life is typical at 10 million operations. Pollution degree 3 means it's rated for conductive pollution environments common in factory floors.