What it is and what it does
The Siemens 3RT1045-1BW40 is a SIRIUS power contactor in the S3 frame size, designed for switching motor loads and resistive loads in industrial control panels. It mounts on standard 35 mm or 75 mm DIN rail via screw and snap-on fastening — no adapter plate needed for the wider rail. Rated 45 kW at 500 V and 21.1 kW at 690 V in AC-3 duty (motor starting/switching under load), it handles the common European 400 V motor range at 37 kW in AC-2. For heavy inrush or reversing duty, AC-4 rating is 66 A at 400 V. Mechanical life is typical 10 million cycles; maximum switching rates range from 300 ops/h in AC-4 to 1000 ops/h in AC-3, so it keeps up with rapid cycling on a conveyor or pump line without derating the coil.
Mounting and wiring in the panel
Footprint is 70 mm wide by 146 mm tall by 152 mm deep. Side-by-side mounting is permitted. Main current circuit uses screw-type terminals. Solid wire accepted in two ranges: 2x (0.5 to 1.5 mm²) and 2x (0.75 to 2.5 mm²), max 2x (0.75 to 4 mm²). Stranded main power wires up to 2x (10 to 50 mm²) — that covers most motor feeds up to the 45 kW rating. Auxiliary/control terminals accept 2x (2.5 to 16 mm²) solid or stranded. Pollution degree 3 rating means it's suited for industrial environments with conductive dust or occasional condensation — typical for a mill floor or machine-side panel, not a clean room.
Environmental and compliance
Operating temperature range is -25 to +60 °C; storage range -55 to +80 °C. The storage spec governs handling during shutdown or transport — the contactor can sit in a cold warehouse and still start up when brought to operating temp. IP20 on the front with cover or box terminal; IP00 at the terminal itself — the terminal area needs finger-safe shrouding in the panel. RoHS compliance date is 05/01/2012, covering the substance prohibitions under EU directive.