PLMU11 - PLMU Series

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Littelfuse Voltage Monitoring Relays
The PLMU11 continuously measures the voltage of each of the three phases to provide protection for 3-phase motors and sensitive loads. Its microcontroller senses under and overvoltage, voltage unbalance, phase loss, and phase reversal. Protection is provided even when regenerated voltages are present. Universal voltage operation from 200 to 480 VAC and standard base connection allows the PLMU11 to replace hundreds of competitive part numbers.


Operation
Upon application of power, a 0.6s random start delay begins and the PLMU11 measures the voltage levels and line frequency and 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, glows red when output de-energizes. undervoltage, overvoltage, and voltage unbalance must be sensed for continuous trip delay before the relay de-energizes. Reenergization is automatic upon fault correction. The output relay will not energize if a fault condition is sensed as 3-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 under voltage trip points. Voltage range is automatically selected by the microcontroller.

Property (Mouseover for details) Value
Input Voltage (V) 200 to 480VAC
Input Tolerance (%) ±15%
Input Voltage Maximum (V) 552VAC
Input Type 3-phase delta or wye with no connection to neutral
Input AC Line Frequency (Hz) 50/60Hz ±2Hz; 200-240VAC: 50/60Hz; 340-420VAC: 50Hz; 400-480VAC: 60Hz
Input Phase Sequence ABC
Output Type Energized when voltages are acceptable
Output Form Isolated SPDT
Output Load Rating (VA) 10A resistive @ 240VAC; 1/4hp @ 125VAC; 1/3hp @ 250VAC; 277VAC max
Random Start Delay ≅0.6s
Reset Time (ms) Automatic
Response Time (ms) Phase loss: ≤200ms; Phase reversal: ≤200ms
Trip Delay Range Adjustable from 0.25-30s
Trip Delay Tolerance (%) ±15%
Overvoltage Trip Voltage (%) 109-113% of the adjusted line voltage
Overvoltage Reset Voltage (%) -2% of the trip voltage
Undervoltage Trip Voltage 88-92% of the adjusted line voltage
Undervoltage Reset Voltage (%) +2% of the trip voltage
Voltage Unbalance Trip Point (%) Adjustable from 2-10%
Voltage Unbalance Reset (%) Selected unbalance %/Reset %: 2/1.5; 3/2.5; 4/3.5; 5/4.5; 6/5.4; 7/6.3; 8/7.2; 9/8.1; 10/9
Severe Unbalance 0.25-2s; disabled when the trip delay is less than 2s
Phase Loss ≥15% unbalance
Isolation Voltage (V) ≥2500V RMS input to output
Surge Protection IEEE C62.41-1991 Level B
Type of Detection Voltage detection with delayed trip and automatic reset
Life Mechanical - 1 x 106; Electrical - 1 x 105
Termination Type Octal 8-pin plug-in
Mounting Method Plug-in socket rated 600V
Operating Temperature -40° to 60°C (-40°F to 140°F)
Storage Temperature (F/C) -40° to 85°C (-40°F to 185°F)
Dimensions 3.03 x 2.39 x 1.78 in. (77.0 x 60.7 x 45.2mm)
Weight (lbs/g) ≅8.6oz (244g)