What it is and what it handles
The Siemens 3RT1026-1AQ64 is a SIRIUS power contactor in the S0 frame size, built for switching motor loads and resistive circuits in industrial control panels. It's rated 11 kW at AC-2 duty (400 V) for slip-ring motors and 15.5 A at AC-4 for reversing or inching duty — the AC-4 number is the one that matters for frequent plugging or jogging applications because it accounts for the higher arcing stress. The contactor snaps onto a 35 mm DIN rail per EN 50022 or screws directly to a mounting plate, so it fits standard panel layouts without adapters.
Coordination and protection
For type 2 coordination (no damage to the contactor on a short circuit), Siemens calls for a gL/gG fuse rated 35 A. If you're running type 1 coordination (contactor may need replacement after a fault), the fuse can go up to 100 A. That 35 A fuse limit is what you size the branch circuit protection around when you want the contactor to survive a fault and keep running. Pollution degree 3 means it's rated for the conductive dust and humidity you'd see in a typical industrial enclosure, not a clean room.
Where it lives in the panel
The contactor measures 45 mm wide, 85 mm tall, and 140 mm deep — that's a compact S0 footprint that leaves room for auxiliary contact blocks on the side. Side-by-side mounting is allowed with a 6 mm gap, so you can pack multiple contactors on a rail without derating. The front of the enclosure is IP20 (finger-safe), but the terminal area is IP00, so it needs to live inside a cabinet, not out in the weather. Operating temperature range is -25 to +60 °C, which covers most plant-floor conditions short of a foundry or freezer.