The Siemens 3RV2922-2CV0 is a SIRIUS undervoltage release designed to trip a 3RV2 motor circuit breaker when its control supply drops below the dropout threshold. It is rated 400 V AC at 50 Hz, with the coil fed from the same AC control voltage. The release snaps onto the breaker via the standard DIN-rail mount — no additional panel space needed beyond the breaker's own 18.5 mm width.
Mounting is snap-on only — no screws required. The release fits 3RV2 breakers in sizes S00, S0, S2, and S3, which covers the common motor-protector range up to about 100 A frame. The front face is IP20 and finger-safe per IEC 60529, so it passes touch-protection checks without a separate cover. Two NO leading auxiliary contacts are integrated. These change state before the main contacts open, giving the PLC or safety relay a pre-trip signal — useful for controlled motor deceleration or process interlock sequencing.