Siemens SIRIUS 3RT5975-5AU31 — Magnet Coil for Size S12 Contactors
The Siemens SIRIUS 3RT5975-5AU31 is a withdrawal-type magnet coil designed for size S12 contactors. This is the replacement coil you pull when the original contactor coil fails — it's the service part, not the full contactor assembly.
What the 277 V AC/DC Rating Means for Fit
The 277 V rating covers both AC (50/60 Hz) and DC control circuits from a single coil — no need to swap coils when switching between control supply types. This is common in North American panels where 277 V phase-to-neutral is standard for lighting and control transformers, and in European 400 V systems tapped phase-to-neutral. The AC/DC compatibility simplifies stocking: one coil serves both architectures.
This coil mounts into the SIRIUS size S12 contactor frame — it's the withdrawable coil assembly, meaning you slide it into the contactor's coil cavity and secure it. No rewiring of the main power circuit; just the control wires to the coil terminals. The AC/DC coil holds at 277 V nominal; verify your control transformer or DC supply delivers that voltage under load.