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. Mounting is screw-and-snap onto 35 mm DIN rail per DIN EN 50022, so it drops into any standard panel rail without adapter plates. The 45 mm width leaves room for a reversing pair or a star-delta cluster in a 600 mm enclosure. IP20 on the front face protects against accidental contact during commissioning; the terminal area is IP00, meaning the panel builder must maintain safe clearance or cover the live terminals inside the 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.
Integration notes for the panel builder
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. Operating temperature range is -25 to +60 °C, which covers most indoor panel environments; above 40 °C, derate the continuous current per the thermal curve in the datasheet. 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. Pollution degree 3 means the contactor is rated for conductive pollution environments — typical in industrial panels without filtered air.