Protection Relays
Voltage Monitoring Relays
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.
8-PIN
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
Features & Benefits
FEATURES
Quick octal 8-pin
mounting
Proprietary
microcontroller
based circuitry
LED diagnostics
BENEFITS
Small footprint with universal mounting: ideal
replacement for hundreds of competitive
part numbers.
Constant monitoring of single-phase, low voltage,
high voltage, voltage unbalance, phase reversal.
Quick visual indicator for trip versus
normal operation.
Ordering Information
MODEL
LINE VOLTAGE
VOLTAGE
TRIP DELAY (FIXED)
UNBALANCE (FIXED)
Isolated, 10A, SPDT
output contacts
Adjustable nominal
voltage set point
Allows control of loads for AC voltages
Allows setting for specific application
voltage to optimize protection
PLM6405
PLM6502
PLM6805
PLM8405
PLM9405
PLM9502
PLM9805
240VAC
240VAC
240VAC
380VAC
480VAC
480VAC
480VAC
4%
5%
8%
4%
4%
5%
8%
5 sec
2 sec
5 sec
5 sec
5 sec
2 sec
5 sec
Simple 3-wire connection
Allows flexibility across wide range of systems
for delta or wye systems
ASME A17.1 Rule 210.6
NEMA MG1 14:30, 14:35
IEEE C62.41-1991 Level B
Complies with safety codes for elevators,
escalators, moving walkways
Complies with safety codes for motors
and generators
Complies with safety codes for surge and
voltage protection
If you don’t find the part you need, call us for a custom product 800-843-8848
© 2016 Littelfuse Protection Relays & Controls
www.littelfuse.com/plm
Rev: 1-A-062116
Protection Relays
Voltage Monitoring Relays
PLM SERIES
Accessories
BZ1 Front Panel Mount Kit
Provides an easy method of through-the-panel
mounting of 8- pin or 11-pin plug-in timers,
flashers, and other controls.
OT08PC Octal 8-pin Socket
8-pin 35mm DIN rail or surface mount. Rated at
10A @ 600VAC. Surface mounted with two #6
screws or snaps onto a 35 mm DIN rail.
LPSM003ZXID (Indicating),
LPSM003Z (Non-indicating) Fuse Holders
Littelfuse POWR-SAFE Dead Front holders
provide optimum protection to personnel for
Class CC and Midget-Style fuses. 600 VAC/DC
0KLK002.T Midget Fuse (2 Amp)
10 x 38 fast acting, high-interrupting capacity,
current-limiting type fuse. 600 Vac/500 Vdc
C103PM (AL) DIN Rail
35 mm aluminum DIN rail available in a 36 in.
(91.4 cm) length.
Specifications
Line Voltage
Type
Operating Voltage
Model
240
380
480
AC Line Frequency
Phase Sequence
Power Consumption
Low Voltage &
Voltage Unbalance
Type
Low Voltage
Trip
Reset Voltage
Voltage Unbalance
Trip
Reset on Balance
Trip Delay
Range
Tolerance
Phase Reversal & Phase Loss
Response Time
Phase Loss
Reset
Output
Type
Form
Rating
Life
Protection
Surge
Isolation Voltage
Mechanical
Mounting*
Dimensions
Environmental
Operating/Storage
Temperature
Weight
Voltage detection with delayed
trip & automatic reset
88 - 92% of adjusted line voltage
Plus 3% of trip voltage
Factory fixed from 4 - 8%
-0.7% unbalance typical
Factory fixed from 2 - 20s
±15%
≤ 200ms
> 35% unbalance
Automatic
Electromechanical relay
Isolated, SPDT
10A resistive @ 240VAC, 277VAC max;
1/2 Hp @ 240VAC; 1/4 Hp @ 120VAC
Mechanical - 1 x 10
7
; Electrical - 1 x 10
5
IEEE C62.41-1991 Level B
≥ 2500V RMS input to output
8-pin plug-in socket rated 600VAC
H
81.3 mm (3.2”);
W
60.7 mm (2.39”);
D
45.2 mm (1.78”)
-40°
to 60°C / -40° to 85°C
≅
4.4 oz (125 g)
Adj. Line
Voltage Range
200-240VAC
360-430VAC
400-480VAC
50/100 Hz
ABC
≅
2W for 240V units
≅
3W for 380 - 480V units
Line Voltage Max
270VAC
480VAC
530VAC
3-phase delta or wye with no connection
to neutral
*CAUTION: Select an octal socket rated for 600VAC operation.
© 2016 Littelfuse Protection Relays & Controls
www.littelfuse.com/plm
Rev: 1-A-062116
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