It carries an AC-3 rating of 18.5 kW at 500 V, meaning it handles the inrush and run currents of a standard three-phase induction motor at that voltage without derating.
The headline motor rating is 18.5 kW at 500 V AC-3 — that is the duty cycle for starting and disconnecting a squirrel-cage motor under full load. At 690 V the same contactor is rated for 10 kW, which reflects the higher voltage stress on the arc chamber. The AC-4 rating (plugging/reversing) is 250 switching cycles per hour, compared to 1 000 per hour for AC-3 — if your application involves frequent inching or reversing, the AC-4 limit governs service life.
If you are managing a multi-year category plan, the SIRIUS platform is Siemens' core industrial contactor family with broad cross-series compatibility — the same accessories, same DIN-rail footprint, and same auxiliary contact blocks across S2 frame sizes. That reduces second-source qualification risk if you ever need to substitute within the family.
Terminal wiring and conductor sizing
The main circuit accepts screw-type terminals: solid conductors 2x (0.25 to 2.5 mm²) and stranded conductors 2x (0.75 to 25 mm²). The wider stranded range covers the full cross-section for a 18.5 kW motor circuit at 500 V — typically 6 to 10 mm² depending on cable length and installation method. The auxiliary/control terminals accept 2x (0.75 to 16 mm²) stranded, which is generous for control wiring.