What it is and where it fits
The Siemens SIRIUS 3RT1025-1AL00 is a size S0 power contactor with a 24 VDC coil, three main NO contacts, and screw-type terminals. It mounts via screw or snap-on onto a 35 mm DIN rail per DIN EN 50022, so it drops straight into a standard panel enclosure alongside other SIRIUS components. Rated motor power is 10 kW at 500 V and 11 kW at 690 V; for AC-4 duty at 400 V it carries 15.5 A, making it suited for reversing or inching applications where the contactor sees frequent switching under load. The auxiliary contact block handles 10 A at 24 V (AC-12), and the coil holds at 24 VDC nominal with a rated frequency of 50 Hz.
DIN-rail footprint and wiring
At 45 mm wide, 85 mm tall, and 91 mm deep, the S0 frame leaves room for side-by-side mounting (permitted by the manufacturer) without derating, provided the ambient stays within -25 to +60 °C during operation. Main-circuit terminals accept 2x (1 to 2.5 mm²) stranded or 2x (2.5 to 6 mm²) solid, up to 2x 10 mm² max. Auxiliary terminals handle 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²), max 2x 4 mm² — typical for control wiring in a panel. IP20 on the front, IP00 at the terminals — the contactor is protected against finger contact on the front face but requires the panel enclosure to shield the wiring zone.