What it is and what it does
The Siemens 3RT1026-1AR04 is a SIRIUS power contactor in the S0 frame size, designed for switching three-phase motor loads in industrial control panels. It carries three normally-open main contacts and two instantaneous auxiliary contacts, all terminated with screw-type terminals. The key motor ratings are 11 kW at 400 V in AC-2 duty (slip-ring motor starting, plugging) and 15.5 A in AC-4 duty (reversing, inching). These are the numbers that govern real-world motor switching, not a higher resistive rating.
Where it fits
Mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022. The S0 frame footprint is 45 mm wide by 85 mm tall by 140 mm deep — a standard slot in most motor control center buckets. Side-by-side mounting is permitted with the specified 6 mm gap, so you can gang multiple contactors without losing thermal coordination. Rated for pollution degree 3 (industrial environment with conductive or dry non-conductive pollution), operating ambient from -25 °C to +60 °C, and up to 2000 m altitude. The front face carries IP20 finger protection; the terminals themselves are IP00 — expect exposed live parts inside the enclosure.
Wiring and coordination
Main circuit screw terminals accept solid or stranded copper: 2x (0.5...1.5 mm²), 2x (0.75...2.5 mm²), or max 2x (0.75...4 mm²) — or AWG equivalents 2x (16...12), 2x (14...10), 1x 8. Strip length is the usual 8-10 mm for this terminal class. For short-circuit coordination, type 2 requires a 35 A gL/gG fuse; type 1 allows up to 100 A gL/gG. The coil operates at 50 Hz with a tolerance of 0.8 to 1.1 times rated voltage — meaning it picks up reliably even on a weak supply.
Lifecycle and sourcing
For a BOM freeze or second-source gate, the closest functional peer is the 3RT1017-1AP01. The 3RT1026-1AR04 carries the S0 frame and the higher AC-2 motor rating (11 kW vs the smaller frame's lower rating); the 3RT1017-1AP01 is a physically smaller frame. They share the same 3-pole NO topology and screw-terminal termination, but the 3RT1026-1AR04 is the heavier-duty option for the same panel slot width.
What the ratings mean for a procurement decision
The AC-2 rating of 11 kW at 400 V is the one that decides fit for most motor applications — it tells you this contactor can handle the starting and running current of an 11 kW slip-ring motor. The AC-4 rating of 15.5 A is the limit for reversing or inching duty cycles. If your load exceeds either, step up to the next SIRIUS frame size. The 10 million mechanical life cycles (typical) mean this contactor is built for high-cycling applications like conveyor lines or pump stations. The electrical life will be lower under load, but the mechanical endurance gives you the headroom for frequent operations.