The Siemens 3RT1945-5AB02 is a SIRIUS magnet coil designed for Size S3 contactors, operating on 24 V AC at 50 Hz with spring-loaded connection technology.
Lifecycle and replacement
This coil is a phased-out product. The manufacturer lists the successor as the SIRIUS 3RT2 series. For a BOM freeze or line-down replacement, the 3RT2 equivalent is the cross-reference to specify.
What the ratings mean for fit
The coil's operating range of 0.8... 1.1 times the rated voltage (24 V AC) means it picks up reliably between about 19.2 V and 26.4 V at 50 Hz. That's the window the contactor's magnetic circuit needs to close fully; outside that range the coil may chatter or fail to seal.
Panel integration
Spring-loaded connection technology — no screwdriver needed for the control wiring. The coil mounts directly onto the SIRIUS S3 contactor frame, which itself snaps onto a 35 mm DIN rail per EN 50022. That's another SKU I don't need for termination hardware.