The Siemens 3RT1934-5AU61 is an AC coil for the SIRIUS S2 contactor family, wound for 277 V at 60 Hz with screw terminals. It's the pull-in coil that makes the contactor pick up — no coil, no switching. The S2 frame size mates with SIRIUS 3RT2 contactors in the same mechanical envelope, so it swaps straight in on a panel rebuild or a coil failure.
The 277 V 60 Hz coil voltage is the standard North American control-voltage tap for a 480Y/277 V distribution system — common in industrial plants running 60 Hz. If your panel is 50 Hz or a different control voltage (120 V, 24 VDC), this coil won't pick up reliably. The S2 physical size matches the SIRIUS 3RT2 contactor range, so it bolts onto the contactor's magnet system without adapters. Screw terminals mean standard ring or fork lugs; no special crimp tool needed.