What It Is and Where It Fits
The Siemens SIRIUS 3RT1035-3BB44-3MA0 is a size S2 power contactor, rated for switching motor loads up to 22 kW at 500 V in AC-3 duty. That AC-3 rating is the one that governs real motor starting — it's the current the contactor handles during acceleration, not just the steady-state resistive load. For high-inertia or plugging applications, the AC-4 rating of 35 A at 400 V tells you the contactor can break stalled-rotor current without welding the main contacts. Mounts on a 35 mm DIN rail per EN 50022, using either the screw clamp or the snap-on foot. Side-by-side mounting is allowed, so you can gang multiple contactors without a gap — useful when you're packing a motor control center row. The IP20 front means it's finger-safe for the panel face; the terminals themselves are IP00, which is normal for a panel interior where the enclosure provides the environmental seal.
Terminal and Wiring
Main circuit terminals are screw-type, accepting 2x (0.75…25 mm²) stranded or 2x (0.25…2.5 mm²) solid. The minimum permissible cross-section at 40 °C is 16 mm² — that's the thermal derating floor for full-rated current. Coil terminals are 24 V DC, drawing 10 A at rated voltage, with a dropout time of 20…25 ms and an arcing time of 10…15 ms. That arcing window matters for coordination with upstream fuses or breakers.
Environmental and Mechanical
Operating temperature range is -25…+60 °C; storage goes from -55…+80 °C. Pollution degree 3 means it's rated for industrial atmospheres with conductive dust or occasional condensation — standard for a panel in a factory hall. Mechanical life is 10 million operations typical; the switching frequency limits (1 200 cycles/h at AC-1, 1 000 at AC-3) give you the thermal duty cycle for repetitive starts.