What it is and what it does
The Siemens 3RT1026-1AQ20 is a SIRIUS power contactor in the S0 frame size, designed for switching motor loads in industrial control panels. It is rated for 11 kW at 500 V in AC-3 duty (squirrel-cage motors) and 11 kW at 400 V in AC-2 duty (slip-ring motors), with an AC-4 reversing/inching rating of 15.5 A at 400 V. The contactor mounts via screw and snap-on onto a 35 mm DIN rail per EN 50022, occupying 45 mm width on the rail. The front face carries IP20 finger protection, while the terminal area is IP00 — standard for panel-mount contactors where the enclosure provides the outer seal.
Key ratings and what they mean for fit
The AC-3 rating of 11 kW at 500 V tells you this contactor handles standard induction motor starting across-the-line up to that load. The AC-4 rating of 15.5 A at 400 V governs plugging and inching duty — the more demanding switching cycle where the contactor makes and breaks stalled-rotor current. If your application requires frequent reversing or jogging, the AC-4 figure is the one that determines contact life. For short-circuit protection, the contactor is coordinated for Type 2 (no weld) with a 35 A gL/gG fuse, and Type 1 (welding allowed but no fire risk) with a 100 A gL/gG fuse. The pollution degree 3 rating means it is suitable for industrial environments with conductive dust or condensation — typical for unsealed control panels. Mechanical endurance is rated at 10 million operations typical, which for a contactor on a conveyor or pump running a few cycles per hour translates to years of service before mechanical wear is a concern. Operating temperature range is -25 to +60 °C, covering most indoor panel environments without derating.
Termination and wiring
Main current circuit uses screw-type terminals accepting 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or max 2x (0.75 to 4 mm²) solid or stranded. For AWG, that's 2x (16 to 12), 2x (14 to 10), or 1x 8. The auxiliary contacts (included as standard on this variant) are rated for 10 A at 24 V, 6 A at 230 V, and 0.3 A at 220 V DC — sufficient for PLC-level control signals. Side-by-side mounting is permitted without derating, saving rail space when grouping multiple contactors. The 6 mm clearance to adjacent devices at the side is the minimum for heat dissipation.