The Siemens 3RT2045-1KB44-3MA0 is a SIRIUS coupling contactor, size S3, designed to switch loads in control panels where a galvanically isolated interface between control and power circuits is required. It mounts on a 35 mm DIN rail per DIN EN 60715 via screw or snap-on fastening, and its mounting position allows ±180° rotation on a vertical surface plus ±22.5° tilt forward/backward — useful when panel layout forces an unconventional orientation.
Rated control supply voltage is 24 V DC. The coil operates between 0.8 and 1.2 times the rated value (19.2 to 28.8 V DC), with an inrush current peak of 2.7 A and a holding current of 6 A at 24 V. Dropout delay on DC is 38 to 57 ms — enough to ride through brief dips but fast enough for most safety circuits. Arcing time runs 10 to 20 ms, so factor that into your contactor sequencing logic.
Load switching capability
Switching frequency varies by duty: 900 operations per hour at AC-1 (resistive), 400/h at AC-2 (slip-ring motors), 1000/h at AC-3 (squirrel-cage motors), 300/h at AC-4 (plugging/inching), and 1000/h at AC-3e (enhanced AC-3). The auxiliary switch is present, with screw-type terminals on the coil and main contacts accepting solid conductors from 2.5 to 16 mm² and stranded from 6 to 70 mm². Auxiliary contact terminals accept 2x (0.5 to 1.5 mm²) solid or 2x (0.75 to 2.5 mm²) stranded.
Shock resistance is 16.3 g / 5 ms (half-sine) and 10 g / 10 ms.