The Siemens 3RT1944-5AG22 is a SIRIUS magnet coil designed for Size S3 contactors, rated 110 V AC at both 50 Hz and 60 Hz. It uses spring-loaded connection technology for the coil terminals — no screwdriver needed on the control wiring, which speeds panel wiring and stays tight under vibration. This coil is the replacement armature for any SIRIUS Size S3 contactor that lost its coil or was ordered without one. The operating voltage tolerance is 0.8 to 1.1 times the rated voltage at 50 Hz, meaning the coil pulls in reliably down to about 88 V and holds through line sags to that floor. At 60 Hz the same tolerance applies. That's a standard IEC coil drop-out margin — nothing unusual, but worth confirming if your control transformer is undersized or your line is long.
Lifecycle reality — this is a phased-out part
The manufacturer lists this as a phased-out product. The official successor is the SIRIUS 3RT2 series, which uses a different coil platform — the 3RT1944-5AG22 does not cross directly to a 3RT2 order code without also replacing the contactor itself. For an existing panel that already has a Size S3 contactor body, this coil is the drop-in service part. Once current stocks are exhausted, the only channel is the surplus and independent-distributor market.
This coil snaps onto the SIRIUS Size S3 contactor magnet system. No DIN-rail space consumed beyond the contactor itself; the coil is captive on the contactor frame. Panel builders should verify the existing contactor is a SIRIUS Size S3 (not S0, S00, S2, S6, S10, or S12) before ordering this coil as a replacement.