What this part is and what it does
The Siemens 3RT1944-5AL21 is a SIRIUS magnet coil — the replaceable solenoid that pulls in the contactor armature. It's sized for Size S3 contactors and terminates via screw terminals. Coil voltage is 230 V AC, rated for both 50 Hz and 60 Hz supply.
What the ratings mean for fit
The 0.8... 1.1 figure at 50 Hz is the operating voltage range as a factor of the rated coil voltage (230 V). That means the coil reliably picks up and holds between roughly 184 V and 253 V AC — a ±15% tolerance that covers typical line sags without dropping out. The same 230 V rating applies at 60 Hz, so it's a straight swap across 50/60 Hz regions.
Deployment context
This coil mounts into a SIRIUS Size S3 contactor frame, which snaps onto a 35 mm DIN rail per EN 50022. The screw terminals match existing panel wiring practices — no crimp-tool change needed for the control circuit.