Carlo Gavazzi Phase, Voltage Monitoring Relay, 3, 3+N Phase, SPDT, 177 → 550V ac, DIN Rail

The Carlo Gavazzi DPB51 is a 3-phase or 3-phase+neutral line voltage monitoring relay for phase sequence, phase loss, over and under voltage with built-in time delay function.

Detects when all 3 phases are present and have the correct phase sequence
Detects if all the 3-phase-phase or phase-neutral voltages are within the set limits
Upper and lower limits separately adjustable