The Siemens SIRIUS 3RT1034-1BB40-1AA0 is a size S2 power contactor with a 24 VDC coil, designed for switching motor loads in industrial control panels. It mounts via screw or snap-on onto 35 mm DIN rail per EN 50022, and the front face carries an IP20 rating — finger-safe for panel interiors. The main circuit uses screw-type terminals, which is the standard for permanent wiring in most IEC panels. Rated 18.5 kW at 500 V in AC-3 duty (motor switching), this contactor handles the typical 3-phase induction motor load profile. The AC-1 resistive rating supports 1200 operations per hour; AC-3 motor duty allows 1000 ops/h, while the more severe AC-4 (plugging/reversing) is limited to 250 ops/h. That spread tells you the thermal capacity is there for high-duty-cycle conveyor or pump applications, but you need to derate for frequent inching or reversing. Coil pickup is guaranteed at 0.8x rated voltage (19.2 VDC), dropout at 1.1x (26.4 VDC). The DC arcing time runs 20–30 ms, which is typical for DC-operated contactors and matters when coordinating with upstream semiconductor fuses or fast-acting breakers.
Termination and Wiring
Main circuit terminals accept solid conductors from 2x (0.5 to 1.5 mm²) up to max 2x (0.75 to 4 mm²), and stranded conductors from 2x (0.75 to 25 mm²). The auxiliary/control circuit accepts 2x (0.75 to 16 mm²) solid or stranded. At 40 °C ambient, the minimum permissible conductor cross-section is 16 mm² — that derating matters if you're packing this into a warm enclosure with other heat sources. Pollution degree 3 (conductive pollution or dry non-conductive that becomes conductive due to condensation) is the rating, which is standard for industrial control panels not in sealed clean rooms. Side-by-side mounting is permitted, so you can gang multiple contactors on the same DIN rail without spacing — but check the thermal derating curve if you do.