SIRIUS power contactor, size S3 — 45 kW at 500 V
The Siemens 3RT1045-3AN20 is a SIRIUS power contactor in the size S3 frame, rated for motor switching at 45 kW at 500 V AC-3 and 21.1 kW at 690 V AC-3. That 500 V rating covers the common IEC 400/500 V distribution levels; the 690 V rating handles the high-voltage end for mining, marine, or heavy industrial panels. AC-3 maximum switching frequency is 1 000 cycles per hour, so it keeps up with frequent start/stop cycles on conveyors or pumps without derating. AC-4 (plugging/reversing) max is 300 cycles per hour — enough for reversing duty but not continuous jogging. Screw-type terminals on the main current circuit accept 2x (10... 50 mm²) stranded or 2x (0.25... 2.5 mm²) solid control wiring. That's a generous lug range for the 45 kW class — no need for adapters on standard motor cables.
Environmental and mounting specs
Front-side protection is IP20 with the cover or box terminal installed; the terminal area itself is IP00. That's standard for panel-mounted contactors — the enclosure provides the overall IP rating. Dimensions: 146 mm high, 70 mm wide, 139 mm deep. The 139 mm depth is the key fit dimension when laying out a shallow backpanel or a compact enclosure.