What It Is and What It Does
The Siemens SIRIUS 3RT1026-1AU00 is a power contactor in the S0 frame size, with three normally open main contacts. It's built for switching motor loads and other inductive circuits in industrial control panels. Rated for 11 kW at 400 V in AC-2 duty (slip-ring motor starting), it handles the high inrush and moderate break currents of that application. For AC-4 duty (plugging/reversing), it's rated at 15.5 A at 400 V — that's the cycle where the contactor takes the full locked-rotor current every time. The main circuit uses screw-type terminals, sized for 2x (0.5... 1.5 mm²), 2x (0.75... 2.5 mm²), max. 2x (0.75... 4 mm²) for solid conductors, and 2x (1... 2.5 mm²), 2x (2.5... 6 mm²), max. 2x 10 mm² for stranded. That's enough for the motor leads this contactor will typically see.
Mounting and Integration
Mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022. The S0 frame is 45 mm wide, 85 mm tall, 91 mm deep — a compact footprint that fits standard panel layouts. Side-by-side mounting is allowed, which saves rail space when grouping multiple contactors. Front protection is IP20 — safe from finger contact in a closed panel. The terminal area is IP00, so live parts are exposed when wiring; the panel door or cover provides the final barrier. Pollution degree 3 means it's rated for industrial environments with conductive dust or occasional condensation.
What the Ratings Mean
The AC-2 rating (11 kW at 400 V) is the one that governs for most slip-ring motor applications — it's the duty class for starting and running. The AC-4 rating (15.5 A at 400 V) is more demanding: it covers reversing and inching, where the contactor makes and breaks the stalled rotor current. If your application cycles the contactor under full load, size on AC-4, not AC-2. Type 1 coordination requires a 100 A gL/gG fuse; Type 2 coordination needs a 35 A gL/gG fuse. Type 2 limits fault damage to the contactor — useful if you want to avoid replacing the contactor after a short circuit. Coil draw at 24 V is 10 A (inrush, likely), dropping to lower holding current — typical for a S0 contactor. The auxiliary contact ratings (at 60 V: 2 A; 110 V: 1 A; 220 V: 0.3 A) are for the control circuit, not the main power.