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The phase balance, sequence and voltage protector trip relay is designed to monitor a three-phase supply for phase imbalance, low, or missing phases or incorrect phase sequence, and to trip a relay if it detects any anomaly. Two versions are available to suit either three-phase three-wire (PSF/G3) or three-phase four-wire (PSF/G4) systems.
Operation
Rotating machines are particularly vulnerable to incorrect phase sequence, and rotate in the wrong direction, potentially leading to physical damage or the risk of injury to personnel. If one phase is lost because of a blown fuse, electric motors can continue to operate (single-phasing) which can result in severe electrical or mechanical damage.
The PSF protector continuously monitors the three-phase supply, with all correct phase sequence applied and all three voltages balanced within the required limits the front panel, the LED will be off and the relay energised. An incorrect sequence, missing phase, out of balance or under voltage condition will de-energise the relay and the LED will illuminate. The set point control allows adjustment of the voltage imbalance, if one phase voltage differs from the other by more than the set percentage, between 5% and 15%, than the relay will de-energise and the LED will illuminate. The time delay function operates only for the voltage imbalance condition. This delay can be used to prevent nuisance tripping due to short term imbalance situations.
Basic Parameters
- Available with three voltage ranges 100-120V, 173-240V and 380-480V (Un)
- Adjustable nominal voltage range
- Adjustable trip delay 0.5-10s
- Adjustable low voltage trip level 50-85%
- Adjustable phase imbalance trip level 5-15%
- Fixed differential (hysteresis) 1%
Click the PDF below to read more about the Crompton Instruments Three Phase Three Wire, Phase Loss/Unbalance and Under Voltage PSF Protector Trip Relay.
