Voltage & phase monitoring relays

Voltage & phase monitoring relays watch supply voltage and phase presence and open a breaker's release coil when the measured value leaves the set tolerance band.

An undervoltage release mounted on an MCCB drops the breaker the moment supply falls below its rated threshold, protecting motors from stalling damage, while phase-monitoring relays detect phase loss or wrong sequence before three-phase loads run unbalanced. Rated coil voltage must match the control supply — common values include 24 V DC, 48 V DC and 100–120 V AC.

• Monitored fault — undervoltage, overvoltage or phase failure/sequence, each protecting a different failure mode
• Rated voltage — match the release coil voltage (24 V DC, 48 V DC, 100–120 V AC) to the control circuit supply
• Mounting — auxiliary releases fit specific MCCB frame sizes per EN 60947-2, standalone relays mount on DIN rail