What this part is and what it does
The Siemens 3RT1944-5AB02 is a SIRIUS magnet coil designed for Size S3 contactors, providing the electromagnetic actuation that pulls in and holds the contactor's main and auxiliary contacts. It operates on a 24 V AC control supply at 50 Hz, with a rated operating range of 0.8 to 1.1 times the rated voltage — meaning the coil reliably picks up and seals in at voltages between about 19.2 V and 26.4 V, and drops out below the lower threshold. The spring-loaded connection technology (cage clamp) accepts solid or ferruled stranded conductors without needing screw torque verification, which speeds panel wiring and resists vibration loosening.
Where it fits in the panel
The coil mounts onto the Size S3 contactor frame via the standard Siemens snap-on interface — no tools needed for the coil swap. The spring-loaded terminals accept 0.2 to 2.5 mm² solid or ferruled stranded wire (per the contactor's terminal spec for the control circuit). Strip length is 8 to 10 mm for the cage clamp. The coil adds no additional DIN-rail width; it sits within the contactor's existing footprint.