© 2016 Littelfuse Protection Relays & Controls

Protection Relays

Voltage Monitoring Relays

www.littelfuse.com/plm

Rev: 1-A-062116

PLM SERIES

Voltage Monitor

Description

The PLM Series is a 3-phase voltage monitor that continuously

monitors each of the three phases. Monitors both delta and

wye systems and no connection to neutral is required. The

microcontroller circuit design protects against undervoltage,

voltage unbalance, phase loss and phase reversal. Protection is

assured when regenerated voltages are present.

Operation

The output relay is energized and the LED glows green

when all voltages are acceptable and the phase sequence is

correct. Under and unbalanced voltages must be sensed for a

continuous trip 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. The LED flashes red during the trip delay, then glows

red when the output de-energizes. The LED flashes green/red if

phase reversal is sensed.

Field Adjustment

Set voltage adjustment knob at the desired operating line

voltage for the equipment. This adjustment automatically sets

the undervoltage trip point. Apply power. If the PLM fails to

energize, (LED glows red) check wiring of all three phases,

voltage, and phase sequence. If phase sequence is incorrect,

the LED flashes green/red. To correct this, swap any two

line voltage connections at the mounting socket. No further

adjustment should be required.

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 trip versus

normal operation.

Isolated, 10A, SPDT

output contacts

Allows control of loads for AC voltages

Adjustable nominal

voltage set point

Allows setting for specific application

voltage to optimize protection

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

Ordering Information

MODEL

LINE VOLTAGE

VOLTAGE

UNBALANCE (FIXED) TRIP DELAY (FIXED)

PLM6405

240VAC

4%

5 sec

PLM6502

240VAC

5%

2 sec

PLM6805

240VAC

8%

5 sec

PLM8405

380VAC

4%

5 sec

PLM9405

480VAC

4%

5 sec

PLM9502

480VAC

5%

2 sec

PLM9805

480VAC

8%

5 sec

If you don’t find the part you need, call us for a custom product 800-843-8848

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