Phase Monitoring Relays

It's vital for 3-phase motors and other rotating equipment that the supplied voltage phases remain stable, balanced, and in the correct order. Several conditions can lead to unintended operation or failure.

• When a phase loss occurs due to a blown fuse, tripped breaker, open circuit, etc., the connected motors and other equipment will draw large amounts of current on the remaining two phases. This can quickly overheat and damage the internal circuitry of these devices
• A phase reversal is a situation where two out of the three phases have swapped in the sequence and can cause the connected equipment to run in the opposite direction
• Phase imbalances exist when one or more of the line-to-line voltages in a 3-phase system are mismatched

Phase monitor relays protect against equipment failure caused by these types of voltage faults and are compatible with typical Wye or Delta systems, protecting against single phasing, even when regenerative voltages are present.

• All relays offer 10A contact rating
• PMRU-TL series relays protect against phase loss, phase reversal, phase unbalance, undervoltage, and overvoltage for 3-phase systems from 190 VAC to 500 VAC
• PMRR-TL series relays provide phase reversal protection in a compact low-cost design; one relay will work on any 3-phase system from 190 VAC to 500 VAC
• PMRRL-TL series relays provide phase loss, phase reversal, and undervoltage protection for 208, 240, and 480 VAC systems
• PMRU-2C series true RMS relays protect against phase loss, phase reversal, phase unbalance, undervoltage, and overvoltage in most generator and other applications from 190 VAC to 600 VAC and with non-sinusoidal waveforms
• DIN rail mount or plug-in socket mount (sold separately), depending on model