The Siemens 3RT1046-1BF44 is a SIRIUS power contactor in size S3, designed for switching motor loads in industrial control panels. It carries a 55 kW rating at 500 V in AC-3 duty, which is the standard category for squirrel-cage motors during starting and disconnection under load — that 55 kW figure is the key selection parameter for sizing the contactor to the motor nameplate. The contactor snaps onto 35 mm or 75 mm standard mounting rail, so panel integration is straightforward: no drilling, just clip and wire.
Ratings and what they mean for fit
AC-3 switching at 400 V delivers 45 kW, and at 690 V it delivers 25.4 kW — the voltage derating is normal for contactors, and the 690 V figure matters if you are running a 690 V motor in a European or marine installation. AC-4 at 400 V is rated at 80 A, which covers plugging and inching duty where the contactor makes and breaks under full locked-rotor current. Mechanical life is typical at 10 million operations, so this contactor is built for high-cycle applications like conveyor lines or pump panels. The main current circuit uses screw-type terminals, accepting solid wire from 2x (0.5... 1.5 mm²) up to max 2x (0.75... 4 mm²) for the control circuit, and stranded wire 2x (10... 50 mm²) for the power circuit. That means the power lugs handle up to 50 mm² stranded — common for 55 kW motor feeds. Degree of pollution 3 means it is rated for conductive pollution environments, typical in industrial panels without climate control. Operating temperature range is -25 to +60 °C, storage from -55 to +80 °C. The IP20 rating on the front with cover or box terminal means the front is touch-safe; the terminal itself is IP00, so the wiring compartment needs enclosure protection. Side-by-side mounting is allowed, which saves panel width when grouping multiple contactors.
Panel integration notes
The contactor measures 146 mm high, 70 mm wide, and 201 mm deep. The 70 mm width is the same as the S3 frame standard, so it shares a common footprint with other SIRIUS S3 devices for uniform panel layout. The depth of 201 mm includes the overhang of the screw terminals — allow clearance for the outgoing cable bend radius, especially with 50 mm² stranded conductors. Fastening method is screw and snap-on onto 35 mm and 75 mm standard mounting rail; no adapter plate needed.