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.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per EN 50022. The S0 footprint is 45 mm wide, 85 mm tall, 100 mm deep — fits standard panel cutouts for this frame class. Side-by-side mounting is permitted; allow 6 mm clearance at the side for heat dissipation when ganged. Front face carries IP20 protection; the terminal area is IP00, so live parts are exposed inside the enclosure — keep the panel door closed during operation.
Short-circuit coordination
For type 2 coordination (no damage to the contactor after a fault), use a gL/gG fuse rated 35 A. 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. Pollution degree 3 (conductive pollution or dry non-conductive that becomes conductive with condensation) — typical for control panels without climate control.
Environmental limits
Operates from –25 °C to +60 °C during operation. Maximum installation altitude 2 000 m without derating. Mechanical life is 10 million operations typical — the coil and armature should outlast the panel's service life under normal cycling.