The Siemens 3UG5616-2CR20 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 across a 90–690 V AC range at 15–70 Hz. Two changeover contacts signal the fault; spring-loaded terminals speed wiring in the panel.
Key ratings in practice
The wide voltage window (90–690 V AC) covers low-voltage distribution up to 690 V line-to-line, so it handles standard 400 V and 480 V systems without a separate PT. The 15–70 Hz frequency range means it works on 50 Hz and 60 Hz networks plus variable-frequency gensets. Two changeover contacts give independent NO/NC pairs for separate alarm and trip paths — one to a PLC input, one to a contactor coil.