What it is and what it does
The Siemens 3RT1934-5AM21 is a SIRIUS magnet coil — the solenoid that pulls in and holds the main contacts of a Size S2 contactor. It is wound for 208 V AC control voltage and works on both 50 Hz and 60 Hz supplies, drawing a pick-up apparent power of 27 V·A and a holding apparent power of 4.4 V·A (typical for the S00/S0 coil family). The screw terminals match the contactor's control-circuit wiring; strip length and ferrule sizing follow the same 0.2–2.5 mm² range as the main power terminals.
What the ratings mean for fit
The 208 V AC coil voltage is the only control voltage variant on this order code — it is not a multi-tap coil. If your panel's control transformer delivers 208 V line-to-line or line-to-neutral (common in North American 208Y/120 V systems), this coil pulls in reliably. The 50/60 Hz dual-frequency rating means the same coil works on either supply without derating. The screw terminal design matches the SIRIUS Size S2 contactor base; no adapter or wiring harness is needed.
Integration into the panel
The coil snaps onto the Size S2 contactor magnet system. The contactor itself mounts on a 35 mm DIN rail per EN 50022, either screw-fixed or snap-on. Side spacing to grounded parts is 6 mm minimum. The IP20 finger-safe terminal cover is standard for the control circuit. For a panel-builder, the coil swap takes under a minute — no need to disconnect the main power wiring.