Product Overview

© 2016 Littelfuse Protection Relays & Controls
Protection Relays
Voltage Monitoring Relays
www.littelfuse.com/plmu11
Rev: 1-A-062116
PLMU11
Voltage Monitor
Description
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 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.
Re-energization 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.
LED Indicator
Steady Green Energized
Steady Red De-engergized (tripped on fault)
Flashing Green Trip Delay
Alternate Flashing Red/Green Phase Reversal
Features & Benefits
FEATURES BENEFITS
Quick octal 8-pin
mounting
Small footprint with universal mounting: ideal
replacement for hundreds of competitive
part numbers.
Proprietary
microcontroller
based circuitry
Constant monitoring of single-phase, low voltage,
high voltage, voltage unbalance, phase reversal.
LED diagnostics
Quick visual indicator for cause of trip. LED
indications include: normal operation, trip delay,
phase reveral, fault
Isolated, 10A, SPDT
output contacts
Allows control of loads for AC voltages
Simple 3-wire connection
for delta or wye systems
Allows flexibility across wide range of systems
ASME A17.1 Rule 210.6
Complies with safety codes for elevators,
escalators, moving walkways
NEMA MG1 14:30, 14:35
Complies with safety codes for motors
and generators
IEEE C62.41-1991 Level B
Complies with safety codes for surge and
voltage protection
Wiring Diagram
F = Fuses
ØA = Phase A = L1
ØB = Phase B = L2
ØC = Phase C = L3
NO = Normally Open
NC = Normally Closed
2A fast acting fuses
recommended for safety
(not required).
Relay contacts are isolated
8-PIN