SIRIUS 3RT1026-1AU04 — size S0 power contactor for motor loads
The Siemens 3RT1026-1AU04 is a SIRIUS power contactor in the compact S0 frame, rated for 11 kW at 400 V in AC-2 and AC-3 duty — the standard motor-switching curve for pumps, fans, and compressors on a 400 V three-phase line. Three NO main contacts handle the power path; screw-type terminals on the main circuit accept up to 2x 10 mm² or 1x AWG 8, which covers the feed for a 22–25 A motor circuit without a separate terminal block. The 45 mm width leaves room for a reversing pair or a star-delta cluster in a 600 mm enclosure.
Motor duty and coordination
At 400 V AC-3 (the common motor-start rating), the contactor switches 11 kW — a 22 A full-load current on a typical 4-pole induction motor. For reversing or plugging duty (AC-4), the rated operational current is 15.5 A at 400 V; that lower figure reflects the increased arc wear from frequent inching or reversing. If the circuit requires type 2 coordination (no weld after a fault), the upstream fuse is gL/gG 35 A; for type 1 coordination (device may be damaged but no fire risk), the fuse can go to 100 A. That gives the panel designer a clear selectivity window. The contactor also carries ratings at 500 V and 690 V — both 11 kW — which is useful for 480 V North American or 690 V European mining/industrial feeds. At 690 V the same power means a lower line current, so the contactor runs cooler in that application.
Auxiliary contact capacity and coil data
The built-in auxiliary contact block (1 NO + 1 NC, instantaneous) handles control-circuit switching across a wide voltage range: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, and 0.3 A at 220 V DC. That covers PLC output cards, relay interfaces, and pilot devices without an add-on block for most simple interlocking. For higher auxiliary current needs, a separate SIRIUS auxiliary contact block snaps onto the front.
The 85 mm height and 140 mm depth fit standard 200 mm deep enclosures with clearance for wiring ducts. Side-by-side mounting is permitted with zero spacing, so a multi-contactor group packs tightly on the rail — useful for star-delta or reversing starters. The 6 mm clearance to adjacent devices on the front is the minimum for air circulation and arc flash containment. Wire termination: main circuit accepts 2x (1–2.5 mm²) or 2x (2.5–6 mm²) stranded, up to 2x 10 mm² maximum. The auxiliary circuit uses smaller terminals: 2x (0.5–1.5 mm²) or 2x (0.75–2.5 mm²), max 2x (0.75–4 mm²). Use ferruled stranded for reliable clamping in the screw terminals.