What It Is and What It Does
The Siemens SIRIUS 3RT1045-1CP04 is a power contactor in the S3 frame size, designed to switch motor loads in control panels and industrial machinery. It carries a 37 kW rating at 400 V under AC-2 duty (slip-ring motor start/run) and 66 A under AC-4 (plugging/inching duty), which tells you it's sized for heavy reversing or jogging applications, not just across-the-line starting.
Mounting and Integration
Mounts via screw or snap-on onto 35 mm and 75 mm standard mounting rail — so it drops into a DIN-rail panel without extra brackets. The S3 frame (146 mm high, 70 mm wide, 188 mm deep) is the mid-size in the SIRIUS contactor family, meaning it fits alongside other SIRIUS gear in a coordinated panel layout. Side-by-side mounting is allowed, which saves rail space when grouping multiple contactors.
Ratings in Context
The AC-3 rating (not explicitly listed here, but the S3 frame typically covers 32–45 kW at 400 V) is the one that governs general squirrel-cage motor switching. The AC-4 rating of 66 A at 400 V is the figure that matters for reversing or inching duty — it's higher than the AC-2 kW number because AC-4 is current-based, not power-based. If you're replacing a contactor in a crane or hoist panel where plugging happens, the AC-4 current is the spec to match.
Environmental and Protection
IP20 on the front with the cover or box terminal installed; the terminal area itself is IP00, so it expects enclosure protection for the wiring compartment. Operating temperature range is -25 to +60 °C, storage from -55 to +80 °C. Pollution degree 3 means it's suited for industrial environments with conductive pollution — no extra conformal coating needed for most panel conditions.