What it is and where it lands
The Siemens 3RT1026-1AK60-0UA0 is a SIRIUS power contactor in the S0 frame size — the middle-duty footprint in the SIRIUS family, sized for motor loads up to 11 kW under AC-2 duty at 400 V. That AC-2 rating covers slip-ring motor starting and reversing, where the contactor sees moderate inrush but regular switching under load. The S0 frame keeps the width to 45 mm, so it fits three across on a standard DIN rail in a 200 mm enclosure without crowding the gland plate. Mounting is screw and snap-on onto 35 mm rail per DIN EN 50022. The screw-type terminals on both main and auxiliary circuits are the workhorse choice for panel shops that prefer a screwdriver over a cage tool — solid wire up to 4 mm² on the control side, stranded up to 6 mm² on the mains.
What the ratings mean for the panel
The 11 kW AC-2 rating at 400 V is the number that decides fit for a motor starter — not the AC-1 resistive rating. AC-2 means the contactor is designed for the higher arc energy of slip-ring motor duty, where the load current stays near rated during switching. If your BOM calls for a contactor on a wound-rotor motor or a reversing application, this rating is the one that governs. The AC-4 rating at 400 V is 15.5 A, which covers plugging and inching duty cycles where the contactor breaks full motor current at standstill. The operating temperature span is -25 to +60 °C — wide enough for unheated enclosures in northern plants or cabinet-adjacent heat from drives. Pollution degree 3 means the contactor is rated for conductive pollution environments typical of industrial panels without hermetic sealing. The IP20 front keeps fingers out; the terminal area is IP00, so live parts are exposed once the enclosure door opens — standard for panel-mount contactors, but worth noting for any maintenance procedure that reaches in live.