SIRIUS 3RT1025-1BB44-0AA1 — Power Contactor, 24 VDC Coil, S0 Frame
The Siemens 3RT1025-1BB44-0AA1 is a SIRIUS power contactor in the S0 frame size, designed for switching motor loads in industrial control panels. It mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 50022, fitting a standard 45 mm wide slot on the rail. Rated for AC-3 duty at 11 kW at 690 V and 10 kW at 500 V, this contactor handles three-phase induction motors up to those power levels. The 24 VDC coil draws 5.4 W during both closing and holding, so the control transformer or power supply needs to sustain that continuous draw. The front face carries an IP20 rating — protected against finger contact but not moisture, so it belongs inside a panel, not on a washdown line. Pollution degree 3 means it tolerates conductive dust and occasional condensation typical of factory-floor enclosures.
Mounting and Wiring
Screw-type terminals on the main circuit accept 2x (1 to 2.5 mm²) solid or stranded, up to 2x 10 mm² maximum. The auxiliary contact terminals take 2x (0.5 to 1.5 mm²) solid or 2x (0.75 to 2.5 mm²) stranded. Strip and torque per the terminal markings — no special tooling needed beyond a standard screwdriver. Side-by-side mounting is allowed with 6 mm spacing at the side, so you can gang multiple contactors on the same DIN rail without derating for heat buildup, provided the ambient stays within -25 to +60 °C during operation.
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), a 63 A gL/gG fuse is permitted. This matters when specifying the branch circuit protection in a UL 508A or IEC 60947-4-1 panel. Mechanical life is rated at 10 million operating cycles typical — that's the contactor itself, not the contacts under load. Electrical life will be lower and depends on the switching current and duty class (AC-3 vs AC-4).