The Siemens 3UG5618-1CR21 is a digitally adjustable monitoring relay from the SIRIUS 3UG5 line monitoring family. It watches three-phase mains for phase failure, phase sequence, asymmetry, frequency deviation, and over- or under-voltage conditions, and it can correct a phase sequence error automatically. The input range covers 90 to 690 V AC at 15 to 70 Hz — wide enough to handle most low-voltage industrial supplies without an external PT. Two changeover contacts give you separate alarm and trip paths, or a single channel with a confirmation feedback loop.
RoHS compliance is declared effective 01 June 2023.
Screw terminals on the 3UG5618-1CR21 — not push-in. Budget an extra minute per wire versus a spring-cage terminal block; the trade-off is a more vibration-resistant connection in a panel that sees regular door-slamming or near a contactor bank. Strip length and torque spec are on the device label; no special tool needed. Packaged dimensions are 127 x 111 x 38 mm — standard SIRIUS 3UG5 width, snaps onto a 35 mm DIN rail. Single unit per box; order multiples if you are stocking spares for a multi-panel line.