SIRIUS S3 power contactor — what it carries and where it lands
The Siemens 3RT1044-1BE40 is a SIRIUS power contactor in size S3, rated for motor switching up to 37 kW at 500 V and 18.6 kW at 690 V. The AC-4 rating at 400 V hits 55 A — that's the severe-duty category for reversing, inching, or plugging loads where the contacts make and break stalled-rotor current. Screw-type terminals on the main circuit accept stranded cable up to 2x 50 mm², so it lands comfortably on a 35 mm or 75 mm DIN rail in a standard MCC or panel enclosure. Coil draws 10 A at 24 V rated value and 2 A at 60 V, with an arcing time of 10 to 15 ms. The mechanical life is typical 10 million operations — that's the contactor body, not the contacts under load, but it tells you the solenoid and spring set are built for a long panel run.
Mounting and wiring — panel fit
Fastening method is screw and snap-on onto 35 mm and 75 mm standard mounting rail. Side-by-side mounting is allowed, so you can gang multiple contactors without a spacing kit — useful when you're packing a motor control center row. Dimensions are 146 mm high, 70 mm wide, 152 mm deep; the depth is the main thing to check against your enclosure depth or gland plate clearance. Solid wire acceptance: 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), max 2x (0.75 to 4 mm²). Stranded main circuit: 2x (10 to 50 mm²). The auxiliary/control terminals are the smaller solid range; the power terminals take the big stranded. Degree of pollution 3 means it's rated for conductive pollution environments — typical in industrial panel interiors where dust and humidity cycle.