What It Is and What It Does
The Siemens 3RT1034-1AU00 is a SIRIUS power contactor in the S2 frame size, built for switching motor loads and resistive loads in industrial control panels. It's rated for 18.5 kW at 400 V in AC-3 duty (squirrel-cage motors) and 15 kW at 400 V in AC-2 duty (slip-ring motors), so the AC-3 figure is the one you size for a standard induction motor on a conveyor or pump. The screw-type terminals on the main circuit accept up to 16 mm² stranded wire at 40 °C, which covers most 18.5 kW motor feeds without needing a lug kit.
Mounting and Integration
Snaps onto 35 mm DIN rail per DIN EN 50022, or screws directly to a backplate. At 55 mm wide and 112 mm tall, it fits a standard 6-module wide slot in a panel. Side-by-side mounting is allowed, so you can gang multiple contactors without a gap — just watch the thermal derating if you pack them tight. The IP20 front means it's protected against finger contact; the terminal area is IP00, so keep live parts behind a panel door or cover.
Termination and Wiring
Main circuit terminals accept solid wire from 0.5 mm² up to 4 mm² (two conductors per clamp) and stranded from 0.75 mm² up to 25 mm². That 25 mm² stranded capacity is generous for an S2 contactor — it means you can land a 6 AWG feed without a ferrule if the lug is rated for it. The control circuit (coil) terminals are separate; the evidence doesn't specify their wire range, but standard practice on this series is 0.5–2.5 mm². Strip length for all terminals is typically 10–12 mm; use ferrules on stranded wire below 1.5 mm² to avoid whiskers under the screw.
Environmental and Compliance
Rated for operation from -25 °C to +60 °C, storage from -55 °C to +80 °C. Pollution degree 3. RoHS compliance with substance prohibition date of 05/01/2012.