Protection Relays
Voltage Monitoring Relays
PLR SERIES
Description
The PLR Series provides a cost effective means of preventing
3-phase motor startup during adverse voltage conditions. Proper
A-B-C sequence must occur in order for the PLR’s output
contacts to energize. In addition, the relay will not energize
when an undervoltage or phase loss condition is present. The
PLR Series protects a motor against undervoltage operation.
The adjustment knob sets the undervoltage trip point.
Operation
The output relay is energized and the LED glows when all
voltages are acceptable and the phase sequence is correct.
Undervoltage must be sensed for a continuous dropout 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.
Field Adjustment:
Turn the adjustment knob fully
counterclockwise and apply three-phase power. The LED should
be ON. Increase adjustment until the LED goes OFF Decrease
.
adjustment until LED glows again. If nuisance tripping occurs,
decrease the adjustment slightly.
NOTE: When properly adjusted and operating in an average system, a voltage unbalance of 10%
or more is required for phase loss detection. When a phase is lost while the motor is running, a
voltage will be induced into the open phase nearly equal in magnitude to the normal phase-to-
phase voltage. This condition is known as regeneration. When regenerated voltages are present,
the voltage unbalance during single phasing may not exceed 10% for some motors. The PLR
Series may not provide protection under this condition. For systems that require superior phase
loss protection, select the PLMU Series.
8-PIN
Wiring Diagram
F = Fuses
ØA = Phase A = L1
ØB = Phase B = L2
ØC = Phase C = L3
NO = Normally Open
NC = Normally Closed
Relay contacts are isolated
2A fast acting fuses recommended for
safety (not required).
Features & Benefits
FEATURES
Continuous monitoring
Industry standard 8-pin
octal plug connection
LED indication
BENEFITS
Prevents 3-phase motor startup when undervoltage
or phase loss condition is present
Eliminates need for special connectors
Quick visual indication of output status and correct
phase sequence
Ordering Information
MODEL
LINE VOLTAGE
PLR120A
PLR240A
PLR380A
PLR480A
95 to 140VAC
190 to 270VAC
340 to 450VAC
380 to 500VAC
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/plr
www.littelfuse.com/
Rev: 1-A-062716
Protection Relays
Voltage Monitoring Relays
PLR SERIES
Accessories
BZ1 Front Panel Mount Kit
Provides an easy method of through-the-panel
mounting of 8- 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
Nominal Voltage
120VAC
240VAC
380VAC
480VAC
AC Line Frequency
Phase Sequence
Response Times
Pull-in
Drop-out
Hysterisis
Pull-in/Drop-out
Output
Type
Form
Rating
Maximum Voltage
Protection
Phase Reversal/Failure
Motors and Generators
Surge
Isolation Voltage
120 & 240VAC
380 & 480VAC
Mechanical
Dimensions
Mounting*
Termination
Environmental
Operating/Storage
Temperature
Weight
3-phase delta or wye with no connection
to neutral
Undervoltage
Dropout Adj. Range
Line Voltage Max.
85 to 130VAC
143VAC
170 to 240VAC
270VAC
310 to 410VAC
480VAC
350 to 480VAC
530VAC
50/60Hz
ABC
≤ 400ms
≤ 100ms
≅
2%
Electromechanical relay, energized when all
voltages are acceptable
SPDT
5A resistive @ 240VAC, 1/4 Hp @ 120VAC
250VAC
ASME A17.1 Rule 210.6
NEMA MG1 14:30, 14:35
IEEE C62.41-1991 Level B
≥ 1500V RMS input to output
≥ 2500V RMS input to output
H
81.3 mm (3.2”);
W
60.7 mm (2.39”);
D
45.2 mm (1.78”)
Plug-in socket
Octal 8-pin, plug-in
0° to 55°C / -40° to 85°C
≅
6 oz (170 g)
*CAUTION: Select an octal socket rated for 600VAC operation.
© 2016 Littelfuse Protection Relays & Controls
www.littelfuse.com/plr
www.littelfuse.com/
Rev: 1-A-062716
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