The Siemens SIRIUS 3RT1035-1AH28-0PA4 is a size S2 power contactor rated for motor switching up to 22 kW at 500 V in AC-3 duty, and 18.5 kW at 400 V in AC-2 duty. The AC-2 rating covers slip-ring motors where the inrush is lower but the switching frequency is higher. It sits in the SIRIUS family, Siemens' modular contactor range for panel builders. The S2 frame is the mid-size in the line, balancing current capacity with panel space: 65 mm wide, 112 mm high, 115 mm deep. That depth is a key dimension for enclosure depth planning — it's the distance from the DIN rail to the furthest projection of the terminals.
Main circuit connections are screw-type terminals. That 25 mm² stranded capacity is generous for a contactor this size — it matches the cable needed for the 22 kW rating without needing a terminal reducer.
Environmental and endurance specs
The mechanical endurance is 10 million operations — that's the contactor body, not the contacts under load. For the electrical life, the maximum switching frequency varies by duty: 1200 cycles per hour in AC-1 (resistive loads), 1000 in AC-3 (squirrel-cage motors), and 300 in AC-4 (plugging/inching). The AC-3 figure is the one to plan around for a conveyor or pump cycling every few seconds.