What it is and what it does
The Siemens SIRIUS 3RT7045-1AH20 is a size S3 contactor with three normally-open main poles, rated for AC-3 switching up to 690 V. That means it handles motor loads — starting and stopping induction motors under load — up to that voltage, with a maximum operating rate of 800 cycles per hour in AC-3 duty. The coil is AC-operated; closing power draw is 0.62 W, holding at 0.27 W. For fault coordination, the upstream fuse requirement is a gL/gG 200 A NH 3NA type.
Mounting and integration
Mounts via screw or snap-on onto 35 mm and 75 mm standard mounting rail — the DIN-rail standard for panel builders. Side-by-side mounting is supported, so you can gang multiple contactors without extra spacing. The mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward, giving flexibility in tight enclosures.
Environmental and terminal specs
Rated IP20 on the front (finger-safe), IP00 at the terminals — so the wiring area is not touch-protected; plan for enclosure-level guarding. Operating temperature range is -10 to +55 °C, storage from -25 to +70 °C. Pollution degree 3 (conductive pollution, typical for industrial control panels). Main and auxiliary/control circuits use screw-type terminals, accepting 2x (0.5…1.5 mm²) solid or stranded, or 2x (0.75…2.5 mm²) finely stranded with ferrules.