What it is and what it does
The Siemens SIRIUS 3RT5056-6AF36 is an S6-frame power contactor for switching motor loads in industrial control panels. Its 1000 V rated insulation voltage and AC-3e maximum of 1000 V mean it handles 690 V motor circuits with margin, and the 121 kW rating at 400 V 60 °C tells you the thermal headroom for a 400 V line feeding a heavy conveyor or pump. Screw-type terminals on the main circuit take conductors up to 95 mm² at both 40 °C and 60 °C, so no derating for a warm enclosure.
Key ratings and what they mean for fit
The 121 kW at 400 V 60 °C is the number that governs real motor switching — it's the AC-3 duty rating at an elevated ambient, not a cold bench figure. At 230 V 60 °C it still delivers 70 kW, so the contactor scales down cleanly for lower-voltage lines. The 1000 V insulation voltage (rated) and AC-3e maximum of 1000 V confirm it's built for 690 V systems with full coordination headroom. Pollution degree 3 means it's rated for industrial atmospheres with conductive dust or condensation — no derating needed for a typical panel environment. The varistor surge suppressor is built in, so you don't need an external RC snubber for coil suppression on the 110-127 V AC coil.
Where it goes and how it mounts
Screw fixing to a mounting plate — not a DIN-rail snap — so plan for drilled holes and a backplate. The mounting position is flexible: vertical surface with +/-90° rotation and +/-22.5° tilt front-to-back. Side-by-side mounting is allowed, which helps when packing multiple contactors in a row for a multi-motor group. The S6 frame is physically substantial: 172 mm tall, 120 mm wide, 170 mm deep — verify your enclosure depth before committing the BOM line.