What it is and what it does
The Siemens 3RT1026-8BB45-1PB2 is a SIRIUS power contactor in the S0 frame size, designed for switching motor loads in industrial control panels. It carries a 24 VDC coil and is rated for 11 kW at 400 V in AC-3 duty — the standard category for squirrel-cage motor starting — so it handles the inrush and break current of a motor up to that power. The AC-4 rating of 15.5 A at 400 V covers reversing or inching applications where the contactor makes and breaks full-load current. Mounting is screw-and-snap-on onto 35 mm DIN rail per EN 50022, which is the standard for panel integration. The S0 frame keeps the footprint compact at 55 mm wide, 85 mm tall, and 101 mm deep — a direct fit into most distribution or motor-control enclosures without extra spacing.
What the ratings mean for fit
The 11 kW rating at 400 V AC-3 is the headline motor-switching figure — it tells you the contactor can start and stop a 400 V three-phase induction motor up to that shaft power. The AC-4 rating of 15.5 A at 400 V is the one to watch for plugging or jogging duty; if your application cycles the contactor under load, that 15.5 A limit governs, not the AC-3 kW number. The coil draws 5.4 W both on closing and holding, which is a constant DC load on the 24 V supply — no surge beyond the pick-up power. Operating temperature spans -25 to +60 °C, so it lives in a warm panel without derating. The front face carries IP20 finger protection; the terminals themselves are IP00, meaning the wiring compartment expects enclosure protection from the panel. Pollution degree 3 suits it for industrial environments with conductive dust or occasional condensation.
Lifecycle and sourcing reality
If you are evaluating a panel originally built around the smaller 3RT1015-1BB42, the S0 frame of this contactor is physically larger — 55 mm wide versus the S00 frame's 45 mm — so verify DIN-rail space and terminal clearance before assuming a drop-in swap. The screw terminals accept up to 2x 10 mm² or 1x 8 AWG for the main circuit, which covers most motor feeds up to the 11 kW rating.