The Siemens SIRIUS 3RT1034-1AP00 is a size S2 power contactor rated for 18.5 kW at 500 V in AC-3 duty, meaning it switches three-phase motor loads up to that power under full-load conditions. At 690 V the same contactor is rated for 10 kW AC-3, so the voltage derating is built in — match the motor nameplate voltage to the correct kW column. The coil is 230 V 50 Hz, with an operate range of 0.8 to 1.1 times rated voltage, which keeps it pulled in during a 20 % sag but drops out cleanly below that. Width is 55 mm, height 112 mm, depth 115 mm — the 115 mm depth matters when the gland plate is tight; allow clearance for the screw-terminal wiring exiting the front. Side-by-side mounting is permitted with no derating for the AC-3 ratings listed, but the switching frequency limits (1200 ops/h AC-1, 1000 ops/h AC-3, 250 ops/h AC-4) govern thermal rise in a densely packed row.
Solid wire accepted: 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), max 2x (0.75 to 4 mm²). Stranded: 2x (0.75 to 25 mm²). For mixed solid/stranded runs the common range is 2x (0.75 to 16 mm²). At 40 °C ambient the minimum permissible conductor is 16 mm² — that is the thermal limit for the terminal, not a sizing recommendation; motor full-load current determines the actual wire size.