Watch how Macromatic's Three-Phase Monitor Relays Protect Motors

Macromatic Three-Phase Monitor Relays, or Protective Relays, provide protection against premature equipment failure caused by voltage faults on three-phase systems.

Depending on the unit selected, it will protect three-phase equipment against: 

• Phase loss - total loss of one or more of the three phases.  Also known as “single phasing.”  Typically caused by a blown fuse, broken wire, or worn contact.  This condition would result in a motor drawing locked rotor current during start-up.  In addition, a three-phase motor will continue to run after losing a phase, resulting in possible motor burn-out.
   
• Phase reversal - reversing any two of the three phases will cause a three-phase motor to run in the opposite direction.  This may cause damage to driven machinery or injury to personnel.  The condition usually occurs as a result of mistakes made during routine maintenance or when modifications are made to the circuit.
   
• Phase unbalance - unbalance of a three-phase system occurs when single phase loads are connected such that one or two of the lines (phases) carry more or less of the load.  This could cause motors to run at temperatures above published ratings.
   
• Undervoltage - when voltage in all three lines of a three-phase system drop simultaneously.  This could result in an increase in current and motor heating and a reduction in motor performance.
   
• Overvoltage - when voltage in all three lines of a three-phase system increase simultaneously.  Could cause a decrease in load current and poor power factor.

Watch the video to learn more.