SIRIUS S0 power contactor — 11 kW at 690 V, screw terminals
The Siemens SIRIUS 3RT1025-1BE44-1AA0 is a Size S0 power contactor rated for motor switching up to 11 kW at 690 V AC-3 and 10 kW at 500 V AC-3 — the AC-3 figure governs the real motor load, not the AC-1 resistive rating. In AC-4 reversing or plugging duty it handles 15.5 A at 400 V, so it suits frequent inching or jogging applications where the contactor sees high electrical wear. The coil draws 5.4 W DC for both closing and holding, which means the control transformer can be sized for a steady load — no inrush spike beyond the sealed power. Mounting is screw-and-snap-on onto 35 mm DIN rail per EN 50022, with a 45 mm width that leaves room for auxiliary contact blocks or a solid-state timer on the same rail. Side-by-side mounting is permitted — no gap needed between contactors — which simplifies panel layout when stacking multiple units for multi-motor groups. The front face carries IP20 finger protection; the terminal area is IP00, so the installer must guard live parts inside the panel. Pollution degree 3 means it tolerates conductive dust and occasional condensation — typical for industrial enclosures not rated clean-room.
Termination and wiring
Main current circuit uses screw-type terminals accepting 2x (1–2.5 mm²) solid, 2x (2.5–6 mm²) stranded, or max 2x 10 mm² — enough for the rated motor currents without piggyback lugs. The auxiliary contact terminal accepts 2x (0.5–1.5 mm²) solid, 2x (0.75–2.5 mm²) stranded, max 2x 4 mm². AWG equivalents for the main contacts are 2x (16–12), 2x (14–10), 1x 8.
Coordination and protection
For type 2 coordination (no damage to the contactor after a short circuit) the required upstream fuse is gL/gG 25 A. For type 1 coordination (contactor may need replacement after a fault) the fuse can be gL/gG 63 A. This lets the panel designer choose between tighter protection or higher fault-clearing capacity depending on the motor branch.