SIRIUS S3 power contactor, 45 kW AC-2 motor switching
The Siemens 3RT1046-1BB44-3MA0 is a SIRIUS S3-size power contactor rated for 45 kW at 400 V in AC-2 duty and 80 A at 400 V in AC-4 duty. The AC-2 rating governs slip-ring motor switching, while the AC-4 figure covers plugging and inching of squirrel-cage motors — the higher inrush and breaking duty of those operations. Frame size S3 means the contactor occupies a 70 mm wide footprint on the DIN rail, with a depth of 201 mm and height of 146 mm. Main circuit termination uses screw-type terminals accepting stranded conductors up to 2x 50 mm². The auxiliary circuit accepts solid wire from 0.5 to 4 mm². This is a panel-mount part designed for screw and snap-on mounting onto 35 mm or 75 mm standard mounting rails.
Ratings and what they mean for your load
The AC-2 rating of 45 kW at 400 V is the figure to use when switching wound-rotor motors or other loads where the starting current is moderate and the break current is near rated. The AC-4 rating of 80 A at 400 V applies when the contactor must handle the high inrush of a squirrel-cage motor during plugging or jogging — a more severe duty that generates more arc energy. For less demanding AC-3 duty (starting and running squirrel-cage motors), the contactor is rated for 55 kW at 500 V and 25.4 kW at 690 V. Maximum switching frequency varies by duty class: 900 operations per hour for AC-1 resistive loads, 850 per hour for AC-3 motor starting, and 250 per hour for the severe AC-4 duty. The mechanical life is rated at 10 million operations typical. Coil holding current at 24 V DC is 10 A, with a dropout time of 14 to 20 ms and arcing time of 10 to 15 ms. The contactor is rated for pollution degree 3, meaning it's suitable for industrial environments with conductive pollution or dry non-conductive pollution that becomes conductive due to condensation. Operating temperature range is -25 to +60 °C, with storage from -55 to +80 °C. The front face carries IP20 protection with the cover or box terminal installed; the terminal area itself is IP00.
Mounting and integration
The 70 mm width and side-by-side mounting capability mean this contactor fits standard 35 mm or 75 mm DIN rails with no additional spacing required between units. The 201 mm depth is the dimension to check against enclosure depth and gland plate clearance. Screw-type terminals on the main circuit accept large stranded conductors up to 50 mm², which is typical for the 45 kW motor circuit this contactor is sized for.