PLR Series – Voltage Monitor Series - Littelfuse PLR Voltage Monitoring Relays Provide Superior Protection

Series: PLR Series – Voltage Monitor
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Littelfuse products are not designed for, and shall not be used for, any purpose (including, without limitation, automotive, military, aerospace, medical, life-saving, life-sustaining or nuclear facility applications, devices intended for surgical implant into the body, or any other application in which the failure or lack of desired operation of the product may result in personal injury, death, or property damage) other than those expressly set forth in applicable Littelfuse product documentation. Warranties granted by Littelfuse shall be deemed void for products used for any purpose not expressly set forth in applicable Littelfuse documentation. Littelfuse shall not be liable for any claims or damages arising out of products used in applications not expressly intended by Littelfuse as set forth in applicable Littelfuse documentation. The sale and use of Littelfuse products is subject to Littelfuse Terms and Conditions of Sale, unless otherwise agreed by Littelfuse. "Littelfuse" includes Littelfuse, Inc., and all of its affiliate entities.

The PLR series is a cost-effective, three-phase voltage monitor that prevents three-phase motor startups during adverse voltage conditions. The proper A-B-C sequence must occur in order for the monitor’s output contacts to energize. In addition, the relay will not energize when an undervoltage or phase loss condition is present. The PLR series protects a motor against undervoltage operation. The adjustment knob sets the undervoltage trip point.

Operation

The output relay is energized and the LED glows when all voltages are acceptable and the phase sequence is correct. Undervoltage must be sensed for a continuous dropout delay period before the relay de-energizes. Reset is automatic upon correction of the fault condition. The output relay will not energize if a fault condition is sensed as power is applied.

Field Adjustment

Turn the adjustment knob fully counterclockwise and apply three-phase power. The LED should be ON. Increase adjustment until the LED goes OFF. Decrease adjustment until LED glows again. If nuisance tripping occurs, decrease the adjustment slightly.

Note: When properly adjusted and operating in an average system, a voltage unbalance of 10 % or more is required for phase loss detection. When a phase is lost while the motor is running, a voltage will be induced into the open phase nearly equal in magnitude to the normal phase-to-phase voltage. This condition is known as regeneration. When regenerated voltages are present, the voltage unbalance during single phasing may not exceed 10 % for some motors. The PLR Series may not provide protection under this condition. For systems that require superior phase loss protection, select the PLMU Series.

Features

  • Continuous monitoring
  • Industry standard 8-pin octal plug connection
  • LED indication

Product Literature

For Technical Questions

Call +1 800-832-3873 or email us at relays@littelfuse.com 

Access specifications, certifications, check availability and order parts below

Catalog #Input
Voltage (V)		Output
Form		Termination TypeMounting MethodDimensionsWeight (lbs/g)Input AC Line Frequency (Hz)Input Phase SequenceInput TypeInput Voltage Maximum (V)Output Load Rating (VA)Output TypeMax. Output
Voltage (V)		Pull-in Response Time (ms)Storage Temperature (F/C)StockSamplesCompare
PLR120A95 - 140 VacSPDTOctal 8-pin plug-inPlug-in socket rated 600V3.2 H x 2.39 W x 1.78 D in. (81.3 x 60.7 x 45.2 mm)0 Kg50 / 60A; B; C3-phase delta or WYE with no connection to neutral1435 A resistive @ 240 Vac; 1/4 hp @ 120 VacElectromechanical relay energized when all voltages are acceptable250≤400; Hysterisis≅2%-40° to 85°C (-40° to 185°F)CheckOrder
PLR240A190 - 270 VacSPDTOctal 8-pin plug-inPlug-in socket rated 600V3.2 H x 2.39 W x 1.78 D in. (81.3 x 60.7 x 45.2 mm)0 Kg50 / 60A; B; C3-phase delta or WYE with no connection to neutral2705 A resistive @ 240 Vac; 1/4 hp @ 120 VacElectromechanical relay energized when all voltages are acceptable250≤400; Hysterisis≅2%-40° to 85°C (-40° to 185°F)CheckOrder
PLR380A340 - 450 VacSPDTOctal 8-pin plug-inPlug-in socket rated 600V3.2 H x 2.39 W x 1.78 D in. (81.3 x 60.7 x 45.2 mm)0 Kg50 / 60A; B; C3-phase delta or WYE with no connection to neutral4805 A resistive @ 240 Vac; 1/4 hp @ 120 VacElectromechanical relay energized when all voltages are acceptable250≤400; Hysterisis≅2%-40° to 85°C (-40° to 185°F)CheckOrder
PLR480A380 - 500 VacSPDTOctal 8-pin plug-inPlug-in socket rated 600V3.2 H x 2.39 W x 1.78 D in. (81.3 x 60.7 x 45.2 mm)0 Kg50 / 60A; B; C3-phase delta or WYE with no connection to neutral5305 A resistive @ 240 Vac; 1/4 hp @ 120 VacElectromechanical relay energized when all voltages are acceptable250≤400; Hysterisis≅2%-40° to 85°C (-40° to 185°F)CheckOrder
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