What this part is and what it does
The Siemens 3RT1944-5BG41 is a replacement magnet coil for SIRIUS Size S3 contactors, rated for 125 V DC control supply voltage with screw-type terminals.
Lifecycle and sourcing reality
Siemens lists this coil as a phased-out product. The official successor is the SIRIUS 3RT2 series — if you're maintaining an existing panel, the 3RT1944-5BG41 remains the drop-in fit for the Size S3 contactor frame; a BOM change to the 3RT2 family requires verifying the mounting footprint and terminal arrangement.
Fit and integration
The coil mounts directly onto SIRIUS Size S3 contactors (e.g., the 3RT1044 frame). Screw terminals accept 2x (0.5... 1.5 mm²) solid or 2x (0.75... 2.5 mm²) stranded — standard control wiring. The 125 V DC coil rating means it pulls in reliably on a nominal 125 VDC control bus; verify your supply stays within the pickup and hold range for DC solenoids.