The Siemens 3RT1934-5AR61 is a SIRIUS magnet coil designed for Size S2 contactors. It provides the electromagnetic actuation for the main contactor, converting an AC control supply into the mechanical force that closes the power contacts. The coil is rated for 400 V AC at 50 Hz and 440 V AC at 60 Hz, with an operating range of 0.8 to 1.1 times the rated voltage — meaning it will reliably pick up and hold between 320 V and 440 V at 50 Hz, or 352 V and 484 V at 60 Hz.
The coil uses screw terminals for the control wiring. The AC control supply must match the coil rating — 400 V AC line-to-line or line-to-neutral depending on the supply configuration. The operating range of 0.8 to 1.1 times rated voltage means the coil will hold in during brownout conditions down to 320 V at 50 Hz, but verify the control transformer sizing if the panel feeds multiple coils.