What it is and what it does
The Siemens 3RT1045-1XF00-0GA0 is a SIRIUS power contactor in frame size S3, designed for switching motor loads and resistive loads in industrial control panels. Its AC-2 rating of 37 kW at 400 V means it handles wound-rotor motor duty cycles where the contactor makes and breaks the rotor circuit under load — a common requirement on crane, hoist, and conveyor applications. At 500 V it carries 45 kW, and at 690 V it carries 21.1 kW, so the same unit covers 400 V and 690 V line supplies without derating the motor frame. The main current circuit uses screw-type terminals, accepting stranded conductors from 10 to 50 mm². Auxiliary contacts accept solid wire from 0.5 to 4 mm². That terminal range covers most motor branch circuits up to 45 kW without needing adapter lugs.
Mounting and integration
Mounts via screw or snap-on onto 35 mm or 75 mm standard DIN rail. Side-by-side mounting is permitted, so you can gang multiple contactors in a motor control center without spacing — useful when panel width is tight. The front face carries an IP20 rating with the cover or box terminal installed, which meets the finger-safe requirement for operator-access areas. The terminal body itself is IP00, so keep that inside the enclosure. Operating temperature spans -25 to +60 °C, storage from -55 to +80 °C. Pollution degree 3 means it's rated for industrial environments with conductive dust or condensation — no derating needed for typical factory-floor conditions.
Switching performance and life
Mechanical life is typical 10 million operations. Maximum switching frequency varies by duty: 900 cycles/hour at AC-1 (resistive), 1000 cycles/hour at AC-3 (squirrel-cage motor start/run), and 300 cycles/hour at AC-4 (plugging or inching). The AC-3 rate of 1000 cycles/hour is the one you'll reference for most conveyor or pump cycling — it's fast enough for frequent start-stop sequences without exceeding the thermal limit. Arcing time is 10 to 15 ms, and the contactor withstands shock at 10.6 g for 5 ms and 6.2 g for 10 ms on AC. DC dropout delay runs 14 to 20 ms — relevant if you're coordinating with a safety relay or PLC output that needs to see the contactor drop within a known window.