The Siemens 3VU2912-4AF0 is an undervoltage release unit designed for the 3VU2.1, 3VU2.2, and 3VU2.3 motor starter series. It trips the starter when line voltage drops below the coil's dropout threshold, preventing an automatic restart when power returns — a standard requirement for machine safety circuits and conveyor interlocking.
Fit & Integration
This undervoltage release mounts directly onto the 3VU2.1, 3VU2.2, or 3VU2.3 motor starter protector — no additional wiring or adapter plate needed. The 110/127V AC coil taps the control transformer secondary; verify the coil voltage matches your control circuit before installation.