What this contactor is and where it fits
The Siemens 3RT1035-1AP04 is a SIRIUS S2-frame power contactor with screw-type terminals, sized for motor switching in control panels. It mounts on a 35 mm DIN rail per EN 50022, either snapped on or screwed down, and occupies a 55 mm width slot on the rail. Its key motor ratings: 18.5 kW at 400 V in AC-2 duty (slip-ring motors, moderate overload) and 35 A at 400 V in AC-4 duty (plugging, inching, reversing). These are the figures that govern fit for a motor branch circuit, not the higher AC-1 resistive rating.
Mounting and wiring constraints
The contactor accepts stranded conductors up to 2x 25 mm² on the main circuit, and solid or stranded wire from 0.5 mm² up to 4 mm² for the coil/auxiliary terminals. The front face carries an IP20 rating (finger-safe), while the terminal area is IP00 — the panel builder must provide additional protection around the power connections. Side-by-side mounting is permitted without derating, which simplifies multi-contactor groupings in a motor control center. The S2 frame depth of 164 mm and height of 112 mm mean it fits standard 200 mm deep enclosures with clearance for wiring.
Lifecycle and sourcing posture
The RoHS compliance date is May 1, 2012, covering the EU RoHS scope. The contactor is rated for pollution degree 3, which means it is suitable for industrial environments with conductive pollution or dry non-conductive pollution that becomes conductive due to condensation.
What the ratings mean for selection
The AC-2 rating of 18.5 kW at 400 V is the one to check for slip-ring motor or moderate-overload applications — it reflects the contactor's ability to make and break motor starting current without excessive contact wear. The AC-4 rating of 35 A at 400 V governs frequent reversing or inching duty, where the contacts must interrupt full-load current at each operation. Operating temperature range is -25 °C to +60 °C, with storage from -55 °C to +80 °C. The mechanical life is typically 10 million operations, which is the contactor body's endurance before wear — electrical life will be lower and depends on the switching load.