Product Overview

© 2016 Littelfuse Protection Relays & Controls
Protection Relays
Voltage Monitoring Relays
www.littelfuse.com/250a
Rev: 1-A-062116
Description
The 250A is a 3-phase, auto-ranging, dual-range voltage monitor
that protects 190-480VAC, 50/60Hz motors regardless of size
from low and high voltage, unbalance/single-phase, and reverse-
phase. The product provides a user selectable nominal voltage
setpoint and the voltage monitor automatically selects between
the 200V and 400V range. The 250A also features adjustable or
manual restart delay.
This unique microcontroller-based voltage and phase-sensing
device constantly monitors the 3-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 Model 250A includes advanced
single LED diagnostics. Five different light patterns distinguish
between faults and normal conditions.
Features & Benefits
FEATURES BENEFITS
Proprietary
microcontroller
based circuitry
Constant monitoring of single-phase, low voltage,
voltage unbalance, phase reversal, harmful power
line conditions.
Auto-sensing wide
voltage range
Automatically senses system voltage between
190 - 480VAC. Saves setup time.
Advanced LED
diagnostics
Quick visual indicator for cause of trip. LED
indications include: normal operation, power-up
restart delay, reverse-phase trip, unbalance/
single-phase trip, high or low voltage trip
Adjustable trip delay
Prevent nuisance tripping due to rapidly fluctuating
power line conditions.
DPDT relay output Allows for versitility to meet wide application needs
Manual Reset
Allows for inspection of equipment before system is
re-energized
3-Phase Voltage/Phase Monitor
250A SERIES
Wiring Diagram
MODEL 250
Ordering Information
MODEL
LINE
VOLTAGE
% OF SETPOINT
DESCRIPTIONLOW
VOLTAGE
TRIP
LOW
VOLTAGE
RESET
HIGH
VOLTAGE
TRIP
HIGH
VOLTAGE
RESET
250A 190-480VAC 90% 93% 110% 107% Provides high and low voltage protection at fixed percentage of nominal voltage.
250600 475-600VAC 90% 93% 110% 107% Provides high and low voltage protection at fixed percentage of nominal voltage.
250A-MET 190-480VAC 85% 88% N/A N/A
Designed for use with Fire Control Panels. Has 2 Form C contacts that operate
independently. Left Form C energizes when voltage conditions are good and
de-energize when a fault condition is detected. Right Form C only energizes
during a reverse-phase condition. No high voltage protection.
250-100-MET 95-120VAC 85% 88% N/A N/A
Designed for use with Fire Control Panels. Has 2 Form C contacts that operate
independently. Left Form C energizes when voltage conditions are good and
de-energize when a fault condition is detected. Right Form C only energizes
during a reverse-phase condition. No high voltage protection.