Three-Phase Monitor Relays
Three Phase Monitoring Relays or Protective Relays, protect motors and equipment from expensive damage due to voltage faults on three-phase systems. Refer to the table below for more information on the level of protection offered by each product, then click one of the Series to see details about a specific product type.
| Series | ||||||
| Phase Reversal | Phase Loss | Undervoltage | Overvoltage |
Phase Unbalance |
Output |
|
| Plug-in Mounting | ||||||
| PCP | Yes | -- | -- | -- | -- | SPDT 10A |
| PLP | Yes | Yes | -- | -- | -- | SPDT 10A |
| PAP | Yes | Yes | Adjustable 75-95% |
-- | -- | SPDT 10A |
| PJPU-FA8X | Yes | Yes | No | Yes |
Indication Only |
SPDT/SPNO 5A* |
| PMP | Yes | Yes | Adjustable 80-95% |
Fixed at 110% | Adjustable 2-10% | SPDT 10A |
| PMP-FA8 | Yes | Yes | Fixed at 90% | Fixed at 110% | Fixed at 6% |
SPDT 10A |
| PMPU-FA8X | Yes | Yes | Fixed at 90% | Fixed at 110% | Fixed at 6% |
SPDT/SPNO 5A* |
| PMPU-FA12X | Yes | Yes | Fixed at 90% | Fixed at 110% | Fixed at 6% |
DPDT 5A* |
| Series | ||||||
| Phase Reversal | Phase Loss | Undervoltage | Overvoltage |
Phase Unbalance |
Output |
|
| DIN-Rail-Mount | ||||||
| PMD | Yes | Yes | Adjustable 80-95% |
Fixed at 110% | Adjustable 2-10% | DPDT 10A |
| PBDU | Yes | Yes | Adjustable 5-25% |
-- | -- | SPDT 5A |
| DIN-Rail-Mount -- PC Series with Communication | ||||||
| PC | Yes | Yes | Adjustable 80-95% |
Adjustable 105-120% |
Adjustable 2-10% | DPDT 5A |
Note: All products work on 50/60 Hz
* Provides isolated contact for alarm circuits | Learn more
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Operation:
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 & 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 & poor power factor.
 3 phase monitor video |
 3-phase monitor relay competitive comparison |
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Macromatic's Three-Phase Monitor Relays Knowledge Base contains general and technical industry articles to help you learn more about Three-Phase Monitor Relays.
