What this contactor is and where it fits
The Siemens 3RT7045-1AP00 is a Size S3 3-pole contactor from the SIRIUS family, designed for switching three-phase motor loads in control panels. It mounts via screw or snap-on onto 35 mm or 75 mm standard mounting rail, so it integrates into a DIN-rail panel layout without extra brackets. Rated insulation voltage is 690 V, with a surge voltage resistance of 6 kV, matching the insulation coordination requirements of industrial switchgear per IEC 60947.
Ratings that decide the fit
The AC-3 maximum operating rate is 800 switching cycles per hour; the AC-4 maximum is 250 1/h. That means this contactor is specced for motor starting duty (AC-3) at a pace typical of conveyors and pumps, not for high-frequency jogging or reversing (AC-4) where the rate drops to a quarter. The auxiliary contacts are rated for PLC-level reliability at 17 V, 5 mA, so they can drive a 24 VDC PLC input directly without a separate interface relay. For the auxiliary contact circuit at 230 V rated value the current is 6 A; at 400 V it is 3 A; at 690 V it is 1 A. These are the switching capacities for the built-in auxiliary contacts — not the main power path — and they determine what control loads (pilot lights, contactor coils, small relays) the auxiliary circuit can handle at different line voltages.
Mounting and wiring notes
Fastening method allows screw fixing or snap-on onto 35 mm and 75 mm standard mounting rail. Side-by-side mounting is permitted, so you can gang multiple contactors without a gap. Mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward — useful when the panel layout is tight. The front face carries an IP20 rating (finger-safe); the terminal area is IP00, so live parts are exposed at the wiring point — panel builders must guard against accidental contact after installation.
Environmental and coordination limits
Operating temperature range is -10 to +55 °C; storage range is -25 to +70 °C. Pollution degree 3 (conductive pollution or dry non-conductive pollution that becomes conductive due to condensation) means it is suited for industrial environments where some dust and humidity are present. For type of coordination 1, the required upstream fuse is a gL/gG NH 3NA rated 200 A. Installation altitude is limited to 2000 m above sea level.