The Siemens 3RV5902-1AV0 is a SIRIUS undervoltage release designed for motor circuit breakers in the S00, S0, S2, and S3 frame sizes. It drops the breaker open when the control supply falls below the dropout threshold, preventing an unexpected restart after a power dip — a standard requirement for machine safety circuits and conveyor interlock schemes. Rated 400 V AC at 50 Hz and 440 V AC at 60 Hz, the coil accepts a 50–60 Hz supply. The control voltage is AC only; no DC variant here. Screw-type terminals on the auxiliary and control circuit make for a straightforward field connection. Snap-on mounting onto a DIN rail keeps panel integration quick. The 19 mm width and 68 mm depth mean it tucks into a single modular space alongside the breaker.
The 20 ms maximum break time means the release opens the breaker within two line cycles at 50 Hz — fast enough to clear a sustained undervoltage before downstream contactors drop out. That timing matters when you're coordinating a multi-motor start sequence. The 690 V rated insulation voltage at pollution degree 3 confirms the release is suitable for 400/480 V line-to-line systems with margin. No derating needed unless you're pushing the upper ambient limit.