The Siemens SIRIUS 3RT6018-1AK22 is a size S00 power contactor, rated for motor switching at 13 kW on a 400 V line at 60 °C ambient — that's the figure that governs real panel duty, not the no-load rating.
Motor power and thermal derating
At 60 °C ambient the contactor delivers 7.5 kW at 230 V, 13 kW at 400 V, and 22 kW at 690 V. The AC-3 maximum operating voltage is 690 V. These are the numbers that decide whether it holds a motor start without welding contacts — always size off the 60 °C column if your panel runs warm.
Width 45 mm, height 57.5 mm, depth 73 mm — fits a standard S00 footprint.
Accepts 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or 2x 4 mm² solid or stranded wire. Minimum permissible conductor at 40 °C is 4 mm²; at 60 °C it's 2.5 mm² — that derating matters if you're running the full rated current in a hot enclosure.