The Siemens SIRIUS 3RT6924-5AG21 is a replacement magnet coil for 7.5 kW motor contactors in size S0, terminated with screw terminals. It is the energizing element that pulls in the contactor armature — if the coil fails, the contactor drops out and the motor circuit opens. Rated for 110 V AC control supply at both 50 Hz and 60 Hz, with an operating voltage range of 0.8 to 1.1 times rated at 50 Hz and 0.85 to 1.1 at 60 Hz. That means the coil will reliably pick up and hold between 88 V and 121 V at 50 Hz, and between 93.5 V and 121 V at 60 Hz — useful to know if your control transformer is lightly loaded or if line drop is a concern.
The screw terminal design matches the existing wiring method on the contactor coil terminals.
The coil draws 7.9 V·A typical holding power at AC. That is the steady-state load the control transformer sees after the contactor picks up. Pick-up inrush is higher — for the SIRIUS S0 contactor family, expect around 27 to 32 V·A momentarily. Verify your control transformer can support the inrush if multiple coils pull in simultaneously. This coil is AC-operated only; there is no DC variant in this order code. If your control circuit is 110 V DC, this coil will not hold in — it will overheat or chatter. Confirm the control supply type before specifying.