The Siemens 3UG5512-2BR21 is a line-monitoring relay that watches three-phase supplies for phase failure, incorrect phase sequence, and asymmetry. It operates across 160-690 V AC at 15-70 Hz, covering the common 50/60 Hz industrial mains and the wider frequency range found on generator or variable-frequency feeds. Two changeover contacts give you independent signalling paths — one to a PLC input, another to a local alarm or contactor coil.
The 160-690 V AC range means this relay can be wired directly across most low-voltage three-phase systems without an external potential transformer — 400 V, 480 V, and 690 V line-to-line are all within its direct measurement window. The 15-70 Hz bandwidth catches not just the standard 50/60 Hz but also variable-frequency drives running at low output frequencies or emergency generators that droop below 50 Hz.
RoHS compliant since 01 June 2023.