What is a Phase Loss? How can I protect my equipment?

Three-Phase Monitor Relays


What is Phase Loss? How can I protect my Equipment?


When one phase of a three-phase system is lost, a phase loss occurs. This is also called ‘single phasing’. Typically, a phase loss is caused by a blown fuse, thermal overload, broken wire, worn contact or mechanical failure. A phase loss that goes undetected can rapidly result in unsafe conditions, equipment failures, and costly downtime.

Under phase loss conditions motors, pumps, blowers, and other equipment draw excessive current on the remaining two phases which quickly overheats the motor windings. Power output is greatly reduced and starting is not possible in this condition. This can potentially leave the equipment in a ‘locked rotor’ state which will overheat and damage the equipment even more rapidly.

Quickly troubleshooting a phase loss and determining the root cause is often difficult. Voltages and currents in a three-phase system do not typically just drop to zero when a phase is lost. Often measurements yield confusing values that require a great deal of complex analysis to correctly interpret. Meanwhile, damage and downtime of the equipment continues to rise.

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A three-phase monitor relay, also called a phase failure relay, is an economical investment that is simple to install. A three-phase monitor relay protects against damage caused by phase loss as well as other three-phase fault conditions. These relays notify of fault conditions and provide control contacts to turn off motors or other equipment before damage occurs for phase loss protection. Further, the relay provides clear indication of the fault present allowing for rapid troubleshooting and reduced downtime.

Phase loss protection relays can be designed into new installations or easily retrofitted into existing installations. Several models are available providing different types of phase loss protection and multiple voltage ranges are offered to fit most three phase applications.

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

Macromatic offers the only phase monitor product of its kind that retains fault indication and continues to monitor all voltages even with a phase loss present. Lose any phase. See it. Every time. Learn more about Macromatic’s Three-Phase Monitor Relays to prevent damage to your critical motors and equipment. Contact Macromatic’s experts for more information on Phase Failure Relays.