The Siemens 3RT2045-3KB44-3MA0 is a SIRIUS coupling contactor in the Size S3 frame, designed for switching loads in control panels where a relay interface isolates the PLC output from the power circuit. The 24 VDC coil draws a 2.7 A inrush peak and holds at 10 A, so verify your DC supply can deliver that surge without droop — a common oversight when sharing a 24 V bus with sensors.
The main contact rating is defined by AC-3 duty (motor switching) at a maximum of 1000 operating cycles per hour, matching the AC-3e rating. That 1000 1/h figure governs the thermal load on the contacts during repetitive start/stop cycles — exceed it and contact wear accelerates. The contactor also carries AC-1 (resistive) at 900 1/h, AC-2 (slip-ring motor) at 400 1/h, and AC-4 (plugging/inching) at 300 1/h, so the buyer must match the operating profile to the correct duty class. Power terminal wiring accepts solid conductors from 2.5 to 16 mm² and stranded from 6 to 70 mm², covering most motor feeder sizes up to roughly 37 kW at 400 V. The auxiliary switch is present (spring-type terminals), and the coil connection uses spring-type terminals as well — no screw tightening needed, which speeds panel assembly but requires a ferrule for fine-stranded wire.