PLM6502 - PLM Series

Series: PLM Questions? Contact Littelfuse Support
Littelfuse Voltage Monitoring Relays
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.

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 3 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.

Property (Mouseover for details) Value
Input Voltage (V) 200 to 240VAC
Input Voltage Maximum (V) 270VAC
Input Type 3-phase delta or wye with no connection to neutral
Input AC Line Frequency (Hz) 50/100Hz
Input Phase Sequence ABC
Output Type Electromechanical relay
Output Form Isolated SPDT
Output Load Rating (VA) 10A resistive @ 240VAC 277VAC max; 1/2hp @ 240VAC; 1/4hp @ 120VAC
Reset Time (ms) Automatic
Response Time (ms) Phase loss: ≤200ms; Phase reversal: ≤200ms
Trip Delay Range 2s fixed
Trip Delay Tolerance (%) ±15%
Undervoltage Trip Voltage 88-92% of the adjusted line voltage
Undervoltage Reset Voltage (%) +3% of the trip voltage
Voltage Unbalance Trip Point (%) 5% fixed
Voltage Unbalance Reset (%) -0.7% unbalance typical
Phase Loss ≥35% unbalance
Power Consumption ≤2W
Isolation Voltage (V) ≥2500V RMS input to output
Surge Protection IEEE C62.41-1991 Level B
Type of Detection Voltage detection with delayed trip and automatic reset
Life Mechanical - 1 x 106; Electrical - 1 x 105
Termination Type Octal 8-pin plug-in rated 600VAC
Mounting Method Plug-in socket
Operating Temperature -40° to 60°C (-40°F to 140°F)
Storage Temperature (F/C) -40° to 85°C (-40°F to 185°F)
Dimensions 3.20 x 2.39 x 1.78 in. (81.3 x 60.7 x 45.2mm)
Weight (lbs/g) ≅4.4oz (125g)