SIRIUS S2 power contactor for motor loads up to 18.5 kW
The Siemens 3RT1034-3BW44 is a SIRIUS S2-frame power contactor rated for 18.5 kW at 400 V in AC-3 duty — the standard motor-switching category per IEC 60947-4-1 — so it handles typical three-phase induction motors up to that power without derating. Screw-type terminals on the main circuit accept 2x (0.75... 16 mm²) stranded or 2x (0.25... 2.5 mm²) solid, covering the range from control wiring to motor feeders. The 55 mm width and screw-and-snap-on mounting to 35 mm DIN rail (DIN EN 50022) make it a direct fit in standard industrial panels.
Ratings that decide the fit
The AC-3 rating of 18.5 kW at 400 V is the headline figure for motor starting: it covers inrush during acceleration and the full-load current once running. For heavy-duty jogging or inching (AC-4), the contactor is rated 29 A at 400 V — that is the current it can interrupt during plugging or reversing without excessive contact wear. The AC-1 resistive rating supports 1 200 operations per hour, AC-3 at 1 000, and AC-4 at 250, so the thermal cycling limits are clear for high-duty applications. Coil control is 48 V DC, with a pick-up drop-out time of 20... 30 ms and an arcing time of 10... 15 ms.
Environmental and compliance notes
Operating temperature range is -25 to +60 °C; storage from -55 to +80 °C. Pollution degree 3 (conductive pollution or dry non-conductive that becomes conductive due to condensation) — typical for industrial control panels without climate control. The front face carries IP20 (finger-safe), while the terminal area is IP00 (no protection). RoHS compliance date is 05/01/2012, indicating the part meets the EU directive from that date forward.