The Siemens 3RT1044-3BW44 is a SIRIUS S3 power contactor with screw-type terminals on the main current circuit. It's rated for motor switching at 30 kW in AC-2 and AC-3 duty at 400 V, and handles 55 A in AC-4 duty at 400 V — the heavy jogging and inching category that wears contacts fastest. Mounts via screw or snap-on onto 35 mm and 75 mm standard DIN rails, with side-by-side mounting permitted. The front face carries IP20 protection with the cover or box terminal fitted; the terminal area itself is IP00, so panel builders need to account for clearance in the enclosure.
Sourcing & Lifecycle
Pricing and availability are confirmed at quote time against an RFQ. This is a fast-moving SIRIUS size that MRO storerooms typically keep as a critical spare for 400 V motor circuits up to 30 kW.
Ratings & Fit
The AC-3 rating at 400 V is 30 kW — that's the standard duty for squirrel-cage motors starting and running. The AC-4 rating of 55 A at 400 V covers plugging, inching, and reversing applications where the contactor makes and breaks full load current repeatedly. Mechanical life is rated at 10 million operating cycles typical. Coil circuit operates at 48 V rated value, with a pickup voltage of 0.8 x rated (38.4 V) and a dropout of 1.1 x rated (52.8 V) — standard for control transformers in 48 VDC panels. Operating temperature range is -25 to +60 °C, storage from -55 to +80 °C. Pollution degree 3, suitable for industrial environments with conductive pollution. Terminal capacity: solid conductors accept 2x (0.25 to 2.5 mm²), stranded accept 2x (10 to 50 mm²) for the main circuit, and 2x (2.5 to 16 mm²) for auxiliary circuits. The 201 mm depth, 70 mm width, and 146 mm height fit the S3 frame footprint — verify panel layout if replacing a different manufacturer's size.