Siemens SIRIUS 3RT1025-1BD40-1AA0 — Power Contactor, S0 Frame
The Siemens SIRIUS 3RT1025-1BD40-1AA0 is a power contactor in the S0 frame size, designed for switching motor loads in industrial control panels. It mounts on a 35 mm DIN rail per EN 50022, with screw-type terminals for the main current circuit. Rated for AC-4 duty at 15.5 A at 400 V, this contactor handles the severe switching conditions of reversing or inching motor starts where the contacts close under full load. For less demanding AC-2 applications (slip-ring motors), it carries 7.5 kW at 400 V. At higher line voltages, the motor power rating reaches 10 kW at 500 V and 11 kW at 690 V, making it suitable for 690 V distribution systems common in mining, marine, and heavy industrial installations. The coil draws 5.4 W for both closing and holding on DC, so the control transformer or DC supply must be sized for that inrush. Auxiliary contacts are rated for 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V — enough for PLC inputs or indicator lamps on the same panel.
Mounting and Integration
Snap-on mounting onto 35 mm DIN rail per DIN EN 50022. S0 footprint is 45 mm wide, 85 mm tall, and 101 mm deep. Side-by-side mounting allowed; 6 mm clearance recommended. Screw terminals accept solid conductors: 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), max 2x (0.75 to 4 mm²). For stranded wire: 2x (1 to 2.5 mm²), 2x (2.5 to 6 mm²), max 2x 10 mm². AWG equivalents: 2x (16 to 12), 2x (14 to 10), 1x 8. Strip length and torque values follow standard Siemens S0 practice. IP20 on the front protects against finger contact; the terminals themselves are IP00, so the contactor must be installed inside a panel or enclosure with a higher overall IP rating.