What it is and where it fits
The Siemens 3RT1035-1BA40 is a SIRIUS S2 power contactor, rated for switching motor loads up to 22 kW at 500 V in AC-3 duty, or 18.5 kW at 400 V in AC-2 duty. The 55 mm width and 112 mm height mean it fits a standard 35 mm DIN rail (screw and snap-on mounting per DIN EN 50022) and leaves room for side-by-side mounting without derating — useful when you're packing multiple contactors into a tight panel row.
Key ratings and what they mean for the panel
AC-3 switching at 1 000 operations per hour is the real-world motor-starting rhythm — conveyor duty, pump cycling, fan starts. The AC-4 rating of 35 A at 400 V covers inching or plugging applications where the contactor breaks full-load current under stalled-rotor conditions. Pollution degree 3 means it's built for the conductive-dust and humidity environment inside a typical industrial enclosure, not a clean room. The screw-type main terminals accept stranded wire up to 2x 25 mm², and solid up to 2x 4 mm². That's enough for the 16 mm² minimum at 40 °C ambient — so you aren't fighting undersized lugs on a warm panel day. Auxiliary contact wiring uses the smaller 0.5-to-1.5 mm² solid range typical for control circuits. Mechanical life is 10 million operations typical, which for a contactor on a line cycling once every 30 seconds gives roughly 8-10 years before replacement. The arcing time of 10-15 ms and DC dropout time of 20-25 ms are what you'd expect for this frame size — no surprises when timing interlocking with a downstream starter.
Mounting and environment
Mounts on 35 mm DIN rail per EN 50022, screw or snap-on. Side-by-side mounting is permitted, so you can gang up multiple contactors on the same rail without an air gap — but watch the ambient temperature: rated operating range is -25 to +60 °C, storage -55 to +80 °C. The front face carries IP20 (finger-safe), while the terminal area is IP00 — standard for panel-mount contactors where the enclosure provides the outer IP rating.