What the 18.5 kW AC-2 rating means for a motor circuit
The Siemens SIRIUS 3RT1035-1AG24 is a Size S2 power contactor rated for 18.5 kW at 400 V in AC-2 duty — the category for slip-ring motor starting and reversing, where the contactor makes and breaks the motor current at low overload. That 18.5 kW figure is the load it can switch under those conditions, not a continuous thermal rating; for AC-3 squirrel-cage motor duty the power capability drops, and for AC-1 resistive loads it rises. The contactor carries a pollution degree 3 rating, meaning it's designed for the conductive environment inside a typical industrial control panel.
Mounting and terminal integration
The 55 mm width and 112 mm height fit a standard S2 footprint; depth is 164 mm, so plan for that behind the gland plate. Front face is IP20; the terminal area is IP00 — finger-safe only when wired and covered.