What it is and what drives the fit
The Siemens 3RT1034-1AN20 is a SIRIUS S2-frame power contactor rated for motor switching in AC-2 duty at 15 kW on a 400 V three-phase line. That AC-2 rating — 15 kW at 400 V — is the number that governs the real motor load: it covers wound-rotor motors and moderate-duty starting. The same contactor also carries 10 kW at 690 V and 18.5 kW at 500 V, so it fits 480 V and 600 V class panels as well. The 55 mm width and snap-on mounting onto 35 mm DIN rail (per DIN EN 50022) mean it occupies a standard three-module slot in a motor control center. Front IP20, terminal IP00 — typical for enclosed panel use.
Mounting and wiring constraints
Screw-type terminals on the main circuit accept stranded conductors up to 2x 25 mm². Solid wire range is 2x (0.5 to 4 mm²) maximum. The dual-wire termination per clamp is useful for looping power through to a downstream overload relay without extra terminal blocks. Side-by-side mounting is allowed — no derating gap required — so you can pack multiple contactors on the same rail. Operating temperature range of -25 to +60 °C covers most indoor panel conditions; storage range extends to -55 to +80 °C.