What it is and what it does
The Siemens 3RT1034-1AG20-ZX95 is a SIRIUS power contactor in size S2, built for switching motor loads in control panels. It carries an AC-2 rating of 15 kW at 400 V and an AC-3 rating of 18.5 kW at 500 V, so it handles the starting and running currents of induction motors up to that power class. The 55 mm width and 112 mm height fit a standard DIN-rail footprint, and the screw-type terminals on the main circuit accept stranded wire up to 25 mm².
Key ratings and what they mean for fit
The AC-3 rating of 18.5 kW at 500 V is the headline motor-switching figure — it tells you this contactor can make and break the locked-rotor current of a motor up to that power, which is the typical duty for conveyor, pump, and fan starts. The AC-2 rating of 15 kW at 400 V covers slip-ring motor duty, where the contactor opens under reduced current. For auxiliary or control circuits, the contactor switches 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V — these cover coil and signal loads. The mechanical life of 10 million operations means the contactor itself will outlast the panel in most cyclic applications.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per EN 50022. Side-by-side mounting is permitted, so you can pack multiple contactors in a row without derating for heat buildup — useful when you're filling a panel with motor starters. The IP20 protection on the front means it's safe from finger contact in a closed enclosure; the terminal area is IP00, so it needs panel-side guarding. Pollution degree 3 means it's rated for industrial environments with conductive dust or occasional condensation.