What this part is and what it does
The Siemens SIRIUS 3RT1944-5AB01 is a magnet coil for Size S3 contactors — the electromagnet that pulls the contactor in and holds it closed. It's a 24 V AC coil rated for 50 Hz operation, with a screw terminal connection for the control circuit. This is the replacement coil for a SIRIUS 3RT1 contactor that has lost its coil or needs a different control voltage.
Lifecycle reality — phased out, successor named
This part is flagged as a phased-out product. The lifecycle stage is listed as current, but the description explicitly calls it a phased-out product with a designated successor: the SIRIUS 3RT2 series. For a BOM freeze or a line-down replacement, the 3RT2 series is the official cross-reference from Siemens. If you're holding a panel with a 3RT1 contactor and need a spare coil, this 3RT1944-5AB01 is the direct fit — but for new designs or long-term spares planning, the 3RT2 successor is the path forward.
Fit and integration — Size S3, screw terminals, DIN rail
This coil mounts onto a SIRIUS Size S3 contactor frame. The contactor itself snaps onto a 35 mm DIN rail per DIN EN 50022. The coil has screw terminals for the 24 V AC control wiring — no special tooling needed, just a screwdriver. The 50 Hz rating means it's designed for 50 Hz mains; using it on 60 Hz without checking the coil's voltage tolerance band (0.8 to 1.1 times rated voltage) could cause overheating or failure to hold in.