What Is Phase Unbalance? How Can I Protect My Equipment?

Three-Phase Monitor Relays


What Is Phase Unbalance? How Can I Protect My Equipment?


Phase unbalance of a three-phase system exists when one or more of the line-to-line voltages in a three-phase system are mismatched. Three-phase power systems and equipment are intended to operate with phases (Lines) balanced. Line-to-line voltages in a three-phase circuit typically vary by a few volts, but a difference that exceeds 1% can damage motors and equipment. The unbalanced voltages cause unbalanced current in the motor windings; unbalanced currents mean an increase of current to at least one winding raising that winding temperature. Increased temperature reduces motor or equipment life leading to premature failure.

A phase unbalance may be caused by unstable utility supply, unbalanced transformer bank, unevenly distributed single-phase loads on the same power system, or unidentified single-phase to ground faults. Single phasing (phase loss) caused by utility supply faults, broken wires, failed fuses, damaged contacts, or malfunctioning overloads can also result in damaging unbalance conditions.

A Macromatic three-phase monitor relay, also known as a phase failure relay, is a cost-effective and easy to install solution to prevent costly damage from phase unbalance to your motors and equipment. A three-phase monitor relay protects against premature equipment failure by monitoring for several common fault conditions including phase unbalance. They notify of a fault condition and offer control contacts to turn off equipment or motor before damage occurs. A clear indication of the fault present is provided by these relays for rapid troubleshooting and reduced downtime.

Three-phase motors and other equipment are commonly used in a variety of industries:

  • HVAC
  • Mining
  • Pumping
  • Elevator
  • Crane
  • Lift
  • Generator
  • Irrigation
  • Petro-Chem
  • Wastewater
  • Industrial Machinery
  • And more

Macromatic offers three-phase monitor relays (phase failure relays) specifically engineered for detecting phase unbalance issues. Protect your equipment and prevent expensive repairs, learn more about Macromatic’s Three-Phase Monitor Relays.