What this SIRIUS contactor is and what it does
The Siemens 3RT1045-1BB48-3MA1 is a SIRIUS power contactor in size S3, built for switching motor loads in control panels. It carries a 45 kW rating at 500 V in AC-3 duty and 21.1 kW at 690 V in AC-3 — that is the motor-switching curve, so it handles induction motors up to those power levels without derating for the starting inrush. The AC-4 rating at 400 V is 66 A, which covers reversing or plugging duty where the contactor breaks full-load current at each reversal. The contactor mounts via screw and snap-on onto 35 mm or 75 mm standard mounting rail, and side-by-side mounting is permitted — no derating gap needed between units on the rail. That saves panel width when grouping multiple contactors for a multi-motor section.
Termination and wiring
Main current circuit uses screw-type terminals. Solid conductors accept 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), and max 2x (0.75 to 4 mm²). Stranded conductors take 2x (10 to 50 mm²) for the power wiring. The control circuit terminals handle 2x (2.5 to 16 mm²) solid or stranded. That range covers standard panel wire up to 50 mm² on the line side — no need for terminal adapters on a 45 kW feed.
Coil and switching performance
The coil is rated 24 V DC with a pick-up value of 0.8 x rated voltage and a drop-out of 1.1 x rated voltage. Arcing time sits at 10 to 15 ms, and the DC operating time is 14 to 20 ms. That means the contactor closes and opens fast enough for standard motor-starting sequences; the arcing window is short enough to keep contact erosion low across the mechanical life of 10 million operations typical.
Environmental and compliance
Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C. Degree of pollution is 3 (conductive pollution, typical for industrial control panels). The enclosure is IP20 on the front with cover or box terminal; the terminal itself is IP00 — so the contactor is intended for installation inside a panel that provides the overall enclosure rating. RoHS compliance date is 05/01/2012.