The Siemens 3RT1026-1BB40-0UA0 is a SIRIUS S0-frame power contactor rated for 11 kW at 400 V in AC-2 duty — the category for slip-ring motor starting and reversing. That 11 kW at 400 V is the rating that governs the motor load it can handle; the AC-4 rating of 15.5 A at 400 V covers plugging and inching duty where the contactor makes and breaks the motor current at full load.
Integration notes
Screw-type terminals on the main circuit accept 2x (0.75... 4 mm²) solid or 2x (1... 2.5 mm²) stranded, with a maximum of 2x 10 mm². The auxiliary contact block at the front carries 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V — enough for a PLC input or a pilot light. That gives the panel builder flexibility — a 35 A fuse keeps the contactor reusable after a fault; a 100 A fuse saves panel space but accepts a sacrificial contactor.