Voltage Monitoring Relays
102A Series
3-Phase Voltage/Phase Monitor
Description
The 102A series is a three-phase, auto-ranging, dual-range voltage monitor that protects 190–600 V ac, 50*/60 Hz motors
regardless of size. This monitor provides a user-selectable nominal voltage setpoint and will automatically select between
the 200 V and 400 V range. A unique microcontroller-based voltage and phase-sensing circuit constantly monitors the
three-phase voltages to detect harmful power line conditions. When a harmful condition is detected, the output relay is
deactivated after a specified trip delay. The output relay reactivates after power line conditions return to acceptable levels.
The 102A monitor includes advanced, single LED diagnostics with five different light patterns that distinguish between
faults and normal conditions. LED indications include normal operation, power-up restart delay, reverse-phase trip,
unbalance/single-phase trip, and high- or low-voltage trip.
*Note: 50 Hz will increase all delay times by 20%.
Features & Benefits
FEATURES
BENEFITS
Constant monitoring of single-phase, low-voltage, high-voltage
(102A-9), voltage unbalance, phase reversal, harmful power
line conditions
Proprietary microcontroller-based circuitry
Automatically senses system voltage between 190–480 V ac. Saves
setup time
Auto-sensing wide voltage range
Advanced LED diagnostics
Quick visual indicator for cause of trip
Prevents nuisance tripping due to rapidly fluctuating power
line conditions
Adjustable trip delay (102A2)
Applications
• Fan motors
• Air conditioners
• Compressors
• Heat, well, and sump pumps
• Small conveyer motors
Littelfuse.com/102A
©2023 Littelfuse, Inc.
Specifications are subject to change without notice.
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Revised: 07/13/2023