The Siemens 3RT1945-5AN21 is a SIRIUS magnet coil for Size S3 contactors, rated 220 V AC at both 50 Hz and 60 Hz, with a screw terminal connection. It is the replacement coil for the S3 frame — if you are servicing a panel with a failed coil on a SIRIUS 3RT1 contactor in this size, this is the drop-in part. The 220 V AC control supply voltage is common across European 230/400 V line panels; the dual-frequency rating means it works on 50 Hz or 60 Hz mains without a change.
Mounts directly onto the SIRIUS Size S3 contactor (3RT103/3RT104 frame). The screw terminals accept the same wire sizes as the contactor's control circuit — typically 0.5 to 2.5 mm² solid or stranded. No additional DIN-rail space is consumed; the coil clips onto the contactor magnet stack. For a panel-builder replacing a failed coil, the swap takes under five minutes: remove the four screws on the contactor arc chute, lift the old coil off the magnet yoke, drop the new one in, and re-torque.
The at 50 Hz value of 0.8... 1.1 is the operating voltage range as a factor of the rated voltage — so the coil holds in from 176 V to 242 V at 50 Hz. Below 176 V it drops out; above 242 V you risk overheating the winding. The same 0.8 to 1.1 factor applies at 60 Hz, giving a 176–242 V window there as well. This is standard for AC-operated contactor coils and matches the SIRIUS family derating guidelines.