The Siemens SIRIUS 3RT1944-5AF02 is a replacement magnet coil for Size S3 contactors in the SIRIUS family. It operates on 110 V AC at 50 Hz, with a rated operating range of 0.8 to 1.1 times the nominal voltage — meaning the coil will reliably pick up and hold as long as the supply stays between roughly 88 V and 121 V AC. The coil uses spring-loaded (cage-clamp) terminals, which speed up panel wiring compared to screw terminals: strip 8–10 mm, push the conductor in, done.
This coil is sized for SIRIUS Size S3 contactors — the frame that handles motor currents roughly in the 38–65 A range (AC-3). The spring-loaded connection technology matches the terminal style on later SIRIUS contactors; if your panel uses screw-type control wiring, you will need a ferrule or pin terminal to fit the cage clamp. The coil mounts directly onto the contactor magnet stack; no DIN-rail space consumed beyond the contactor itself.