SIRIUS S0 power contactor — 4-pole, 11 kW AC-2 at 400 V
The Siemens 3RT1326-1AU00 is a SIRIUS S0-frame power contactor with four main poles, all normally open, rated for 11 kW at 400 V in AC-2 duty — the duty class for slip-ring motor starting and plugging, where the contactor makes and breaks the load current at reduced inrush. That 11 kW figure at 400 V is the load the contactor can switch under those conditions, not a continuous thermal rating; for continuous current the AC-1 resistive rating governs, and for across-the-line squirrel-cage starts you need the AC-3 or AC-4 curve. The S0 frame is the middle size in the SIRIUS contactor family, sized for motor loads up to about 18.5 kW in AC-3 depending on the variant, but this specific order code is configured for the higher electrical endurance of AC-2 service.
Mounting and panel integration — DIN rail, S0 footprint
The S0 envelope is 61 mm wide, 85 mm tall, 91 mm deep — a compact footprint that leaves room for a full motor starter combination (contactor + overload relay + fuse disconnect) in a 200 mm wide enclosure bay. The IP20 front-of-terminal protection is adequate for enclosed panel use; the terminal body itself is IP00, so live parts are exposed when the contactor is removed from the panel — standard for open-device contactors.
Termination and wiring — screw terminals, dual-wire capacity
Main and auxiliary circuits use screw-type terminals. The main circuit accepts solid or stranded conductors: 2x (1 to 2.5 mm²), 2x (2.5 to 6 mm²), or a single 10 mm². The auxiliary circuit accepts 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or max 2x (0.75 to 4 mm²). AWG equivalents are 2x (20 to 16) and 2x (18 to 14) for the main, same for aux. This dual-wire capacity is useful for looping the supply through the contactor to feed a downstream device without a separate terminal block — common in motor starter assemblies. The fine-stranded with ferrule range is the same as the solid range, so no special preparation is needed for stranded control wiring.
Coordination and protection — Type 1 and Type 2 fuse ratings
For short-circuit protection the contactor is coordinated with gL/gG fuses: Type 2 coordination requires a 35 A fuse, Type 1 coordination a 63 A fuse.