The Siemens SIRIUS 3RT1924-5AH21 is a magnet coil for Size S0 contactors, rated 48 V AC at both 50 Hz and 60 Hz. It snaps onto the contactor's coil terminals via screw connections — the same footprint as the standard S0 coil interface.
Lifecycle reality — phased out, successor available
This coil is a phased-out product. The official Siemens preferred successor is 3RT2924-5AH21, which drops into the same Size S0 contactor and shares the same 48 V AC 50/60 Hz coil rating. If you are stocking spares or filling a BOM line, the successor is a direct form-fit-function swap — no rewiring, no mounting change.
Sourcing posture
For the successor 3RT2924-5AH21, we can also quote that alongside the original code if you need a drop-in replacement for a BOM freeze.