The Siemens SIRIUS 3RT1935-5AU61 is a replacement magnet coil for Size S2 contactors, wound for 277 V AC at 60 Hz with screw terminals. It's the coil you'd order when the original in a SIRIUS S2 contactor fails — same footprint, same mounting, direct swap.
Lifecycle and Sourcing Reality
The lifecycle stage is listed as current, but the product description flags it as a phased-out product with the successor being the SIRIUS 3RT2 series. This means while it's still available through distribution channels, it's not a long-term production part. For a BOM line that needs this exact voltage and frequency, we source it to order against an RFQ — availability and pricing are confirmed at quote time. If you're designing a new panel, the 3RT2 series coil is the forward path.
What the Ratings Mean for Fit
Rated at 277 V AC, 60 Hz — that's a North American line-to-neutral voltage on a 480Y/277 V system. The 60 Hz spec is fixed; a 50 Hz coil won't pull in reliably on this winding. Screw terminals match the existing SIRIUS S2 contactor base, so no re-termination or adapter needed. Size S2 covers contactors in the 38–65 A AC-3 range, so this coil is sized for that mechanical stroke and holding force.
Panel Integration
The coil mounts directly onto the SIRIUS S2 contactor — no additional bracket or wiring harness. Screw terminals accept the same ring or fork terminals as the original. If you're replacing a failed coil in an existing panel, verify the contactor base is SIRIUS Size S2; the 3RT2 successor uses a different mechanical interface and won't interchange.