What this part is and why it matters
The Siemens SIRIUS 3RT1934-5AN21 is a replacement magnet coil for Size S2 contactors in the SIRIUS family, terminated with screw terminals and rated for 220 V AC control supply at both 50 Hz and 60 Hz. This is a phased-out product; the official successor is the SIRIUS 3RT2 series. If you're holding a BOM line with this order code, the coil itself is still a standard Size S2 fit — the mounting footprint and terminal arrangement match the existing contactor frame — but the supply channel has shifted to the 3RT2 generation.
Coil ratings and what they mean for fit
The coil draws 0.8 to 1.1 A at 50 Hz (220 V). That's the holding current once the contactor is sealed — the inrush (pick-up) will be higher, but the steady-state load on the control transformer is what this figure governs. At 60 Hz the same 220 V coil holds within a similar band, so a panel wired for 50 Hz doesn't need a coil swap if the line frequency changes. The screw terminal connection is the standard Size S2 footprint — same as the contactor base. If your panel was built around a 3RT1 contactor, this coil drops in without rewiring the control circuit.