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Phase monitoring relays

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Phase monitoring relay F&f Filipowski PF-431 Screw connection AC

Phase monitoring relay F&f Filipowski PF-431 Screw connection AC

€59.44 +VAT
PLN 278.00
  • Manufacturer: F&f Filipowski
  • Manufacturer Code: PF-431
  • EAN: 5908312594024
  • Type of electric connection: Screw connection
  • Voltage type for actuating: AC
  • Number of contacts as normally closed contact: 0
  • Number of contacts as normally open contact: 3
  • Number of contacts as change-over contact: 0
Response time: usually up to 2 days
Phase monitoring relay F&f Filipowski PF-451 Screw connection AC

Phase monitoring relay F&f Filipowski PF-451 Screw connection AC

€60.60 +VAT
PLN 283.41
  • Manufacturer: F&f Filipowski
  • Manufacturer Code: PF-451
  • EAN: 5908312594031
  • Type of electric connection: Screw connection
  • Voltage type for actuating: AC
  • Number of contacts as normally closed contact: 0
  • Number of contacts as normally open contact: 3
  • Number of contacts as change-over contact: 0
Response time: usually up to 2 days
Phase monitoring relay F&f Filipowski PF-441 Screw connection AC

Phase monitoring relay F&f Filipowski PF-441 Screw connection AC

€55.15 +VAT
PLN 257.95
  • Manufacturer: F&f Filipowski
  • Manufacturer Code: PF-441
  • EAN: 5908312594048
  • Type of electric connection: Screw connection
  • Voltage type for actuating: AC
  • Number of contacts as normally closed contact: 0
  • Number of contacts as normally open contact: 3
  • Number of contacts as change-over contact: 0
Response time: usually up to 2 days
Phase monitoring relay Siemens 3UG45122AR20 Spring clamp connection AC

Phase monitoring relay Siemens 3UG45122AR20 Spring clamp connection AC

€81.79 +VAT
  • Manufacturer: Siemens
  • Manufacturer Code: 3UG45122AR20
  • EAN: 4011209642546
  • Type of electric connection: Spring clamp connection
  • Voltage type for actuating: AC
  • Number of contacts as normally closed contact: 0
  • Number of contacts as normally open contact: 0
  • Number of contacts as change-over contact: 1
Response time: usually up to 3 days
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Phase monitoring relays

Phase monitoring relays belong to the monitoring relays that are used in automation and control systems to control phase voltages in three-phase AC networks. Their role is to protect electric motors supplied from a three-phase network against voltage failure in at least one phase. They also prevent voltage asymmetry between phases. They also protect against damage to the operating contactor and change of the phase connection sequence, which may result in incorrect operation or damage to the motor.

Phase control relays are useful in three-phase networks, and their installation in the system is of great importance in the event of a power failure in one of the phases, or in the event of voltage unbalance. They detect cases where there is incorrect sequence of the power phases, which prevents the motor from rotating in the wrong direction.

Phase monitoring relays can be used to protect single motors or a group of motors. In such cases, they are powered by a common contactor or a magnetically latched switch. They are used for any three-phase motors, maintenance-free devices, e.g. fans, air conditioners, welders, pumps, cooling devices, computers. F&F relays perform very well in this role.

These types of relays are also used to protect equipment in a small installation from one external source. The phase control relay has an auto-reset capability to protect the motors without the compulsion of sensory control. In the event of a phase failure, the motor will be disconnected, and when the specified conditions are restored, the relay is reset.

Tasks of phase control relays

The sequence and phase failure relay detects accidents that could eventually damage the engine. The main tasks of phase control relays, in addition to detecting incorrect phase sequence and preventing the motor from starting in the wrong direction, also include immediate motor shutdown in the event of a change in the phase sequence in the supply voltage. The relay detects a phase failure and switches the output contact instantaneously. It detects the unbalance of the supply voltage (exceeding 40%) and, similarly to a phase failure, switches the output contact. The role of the relay also boils down to switching off the device when the supply voltage drops symmetrically below 0.8Un.

How phase control relays work

A loss of voltage in at least one phase, or voltage unbalance between phases above the threshold, will result in the motor being shut down. Usually, it is delayed (depending on the manufacturer, from one to several seconds), which allows to protect the device against accidental disconnection in the event of a temporary voltage drop. It is switched on again automatically when the voltage rises by 5V above the activation voltage. It is the value of the voltage hysteresis. The phase monitoring relay detects voltage failure. In normal operation, the three-phase voltage input phases present in the standard network are balanced.

When any phase is unbalanced by more than 12% with respect to the other two (high or low), phase failure occurs, the sensor network supplies an output voltage to activate the transistor circuit. As a consequence, the main output relay (phase-noise relay) trips. Most of the phase control relays have an adjustable switch-off and recovery delay and a different voltage unbalance threshold.

How to mount the relays

Most types of relays allow for easy surface mounting and mounting on a TH 35mm rail. They do not require a neutral conductor, and surface-mounted versions are available with a wire connection and / or connectors. Installation and commissioning is relatively easy as it does not require additional measurements and settings. It can be mounted in any position.