PLMU Series - Voltage Monitor

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.

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.

Access specifications, certifications, check availability and order parts below

Catalog #Input
Voltage (V)
Termination TypeMounting MethodDimensionsWeight (lbs/g)
PLMU11200 to 480VACIsolated SPDTOctal 8-pin plug-inPlug-in socket rated 600V3.03 x 2.39 x 1.78 in. (77.0 x 60.7 x 45.2mm)≅8.6oz (244g)