The Siemens 3RT1944-5BF41 is a SIRIUS magnet coil designed for Size S3 power contactors. It's the replacement coil you'd pull off the shelf when the original coil on a 3RT1 S3 contactor fails in the field — screw-terminal connection, 110 V DC control supply voltage. This is a phased-out product; the official successor is the SIRIUS 3RT2 series coil.
What the 110 V DC coil rating means on site
110 V DC is a common control voltage in industrial panels, especially where DC bus distribution is used for contactor coils. The screw terminals on this S3 coil match the existing wiring on 3RT1 contactors — no need to re-terminate or swap connectors. If you're swapping a failed coil in a live panel, verify the control supply is isolated and discharged before you touch the terminals; DC coils don't drop out as cleanly as AC on power loss.
Panel fit and mechanical integration
This coil mounts directly onto a SIRIUS Size S3 contactor frame — it's not a standalone device. The screw-terminal connection accepts the same wire gauges as the contactor's control circuit. No DIN-rail space consumed beyond the contactor itself; the coil is an integral part of the contactor assembly.