SIRIUS S3 power contactor — 3RT5045-1BM40
The Siemens 3RT5045-1BM40 is a SIRIUS S3 power contactor, screw-type terminals on main and auxiliary circuits, rated for motor loads up to 21.1 kW at 690 V. It snaps onto standard 35 mm or 75 mm DIN rail — no adapter plate needed. The 70 mm width and 152 mm depth fit a standard panel layout; side-by-side mounting is permitted without derating gaps.
What the ratings mean for your panel
The 690 V motor rating of 21.1 kW is the AC-3 switching capacity — that's the real-world figure for induction motor starts. The insulation voltage is rated 1 000 V, giving headroom in 690 V systems. For short-circuit protection the spec calls for a gL/gG fuse rated 160 A (type of assignment 2) — that's the coordination point for your selectivity study. Operating temperature range is -25 to +60 °C, which covers most indoor panel environments. The mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward — useful when fitting into tight enclosures or angled sub-panels.
Panel integration
Screw-type terminals on both main and control circuits — accepts 2x (2.5 to 16 mm²) solid/stranded or 2x (10 to 1/0 AWG). Strip length per standard practice; torque values are on the terminal marking. The contactor accepts an auxiliary switch add-on (product extension auxiliary switch = yes), so you can add feedback contacts without changing the base unit.