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

Series: PLMU 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 PLMU (PLMU11) series is a three-phase voltage monitor that continuously measures the voltage of each of the three phases to provide protection for motors and sensitive loads. Its proprietary microcontroller-based circuitry senses under and overvoltage, voltage unbalance, phase loss, and phase reversal. Protection is provided even when regenerated voltages are present. Universal voltage operation and standard base connection allows the PLMU11 to replace hundreds of competitive part numbers.

Operation

Upon application of power, a 0.6 s random start delay begins, and the PLMU11 measures the voltage levels and line frequency and then selects the voltage range. The output relay is energized and the LED glows green when all voltages are acceptable and the phase sequence is correct. LED flashes green during trip delay and glows red when output de-energizes. Undervoltage, overvoltage, and voltage unbalance must be sensed for continuous trip delay before the relay de-energizes. Re-energization is automatic upon fault correction. The output relay will not energize if a fault condition is sensed as three-phase input voltage is applied. The LED alternately flashes red/green when phase reversal is sensed. Line voltage is selected with the knob, setting the over and undervoltage trip points. The voltage range is automatically selected by the microcontroller.

LED Indicator

Steady green = Energized
Steady red = De-energized (tripped on fault)
Flashing green = Trip delay
Alternate flashing red/green = Phase reversal

Features

  • Proprietary microcontroller-based circuitry
  • Quick octal 8-pin mounting
  • LED diagnostics
  • Isolated, 10 A, SPDT output contacts
  • Simple three-wire connection for delta or wye systems – no connection to neutral
  • ASME A17.1 Rule 210.6
  • NEMA MG1 14:30, 14:35
  • IEEE C62.41-1991 Level B

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 Tolerance (%)Input TypeInput Voltage Maximum (V)Output Load Rating (VA)Output TypeOvervoltage Reset Voltage (%)Overvoltage Trip Voltage (%)StockSamples
PLMU11200 - 480 VacIsolated SPDTOctal 8-pin plug-inPlug-in socket rated 600V3.03 H x 2.39 W x 1.78 D in. (77 x 60.7 x 45.2 mm)0 Kg50 / 60 ±2; 200 - 240 V ac: 50 / 60; 340 - 420 V ac: 50; 400 - 480 V ac: 60A; B; C±15%3-phase delta or WYE with no connection to neutral55210 A resistive @ 240 Vac; 1/4 hp @ 125 Vac; 1/3 hp @ 250 Vac; 277 Vac maxEnergized when voltages are acceptable-2% of the trip voltage109 - 113% of the adjusted line voltageCheckOrder
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