Contactor selection memo
The Siemens SIRIUS 3RT1026-3BW40 is a size S0 power contactor rated for motor switching at 11 kW on 500 V AC-3 and also 11 kW on 690 V AC-3 — same power at both voltages, meaning the current draw drops as line voltage rises, so the contactor is current-limited at the lower voltage. For reversing or plugging duty (AC-4), it handles 15.5 A at 400 V. The coil is DC-operated, with a constant 5.4 W closing and holding power — no AC hum, and the coil driver sees a steady load regardless of line frequency.
Short-circuit coordination
For type 1 coordination (contactor may need replacement after a fault, but the panel is safe), the fuse can go up to 100 A. This matters for selectivity studies — the upstream breaker must coordinate with the chosen fuse rating to clear the fault before the contactor welds.
Termination and wiring
Main current circuit terminals are screw-type, accepting solid or stranded conductors: 2x (0.25–2.5 mm²), 2x (1–2.5 mm²), 2x (2.5–6 mm²), or up to 2x 10 mm². AWG equivalents: 2x (16–12), 2x (14–10), or 1x 8.
Environmental limits
Maximum installation altitude 2 000 m without derating.