Protection Relays
Voltage Monitoring Relays
250A SERIES
3-Phase Voltage/Phase Monitor
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.
Wiring Diagram
Features & Benefits
FEATURES
Proprietary
microcontroller
based circuitry
Auto-sensing wide
voltage range
MODEL 250
BENEFITS
Constant monitoring of single-phase, low voltage,
voltage unbalance, phase reversal, harmful power
line conditions.
Automatically senses system voltage between
190 - 480VAC. Saves setup time.
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
Prevent nuisance tripping due to rapidly fluctuating
power line conditions.
Allows for versitility to meet wide application needs
Allows for inspection of equipment before system is
re-energized
Advanced LED
diagnostics
Adjustable trip delay
DPDT relay output
Manual Reset
Ordering Information
% OF SETPOINT
MODEL
LINE
VOLTAGE
LOW
VOLTAGE
TRIP
LOW
VOLTAGE
RESET
HIGH
VOLTAGE
TRIP
HIGH
VOLTAGE
RESET
DESCRIPTION
250A
250600
250A-MET
190-480VAC
475-600VAC
190-480VAC
90%
90%
85%
93%
93%
88%
110%
110%
N/A
107%
107%
N/A
Provides high and low voltage protection at fixed percentage of nominal voltage.
Provides high and low voltage protection at fixed percentage of nominal voltage.
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.
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.
Rev: 1-A-062116
250-100-MET
95-120VAC
85%
88%
N/A
N/A
© 2016 Littelfuse Protection Relays & Controls
www.littelfuse.com/250a
Protection Relays
Voltage Monitoring Relays
250A SERIES
Specifications
Frequency
Functional Characteristics
Voltage Unbalance (NEMA)
Trip
Reset
Trip Delay Time
Low Voltage, High Voltage
Unbalance, Phasing Faults
Restart Delay Time
After a Fault or Complete
Power Loss
Output Characteristics
Output Contact Rating
(DPDT - 2 Form C)
Pilot Duty
General Purpose
Temperature Range
Trip & Reset Accuracy
Maximum Input Power
Relative Humidity
Terminal Torque
Wire Size
Transient Protection
(Internal)
Approvals
UL
CSA
CE
Dimensions
Weight
Mounting Method
50*/60Hz Low Voltage
6%
4.5%
4 seconds
2 seconds
Manual, 2-300 seconds adj.
480VA @ 240VAC
10A @ 240VAC
-40° to 70°C (-40° to 158°F)
±1%
5W
Up to 95% non-condensing per IEC 68-2-3
7 in.-lbs.
12-18AWG
IEC 61000-4-5;1995 ±6kV
UL508 (File #E68520)
CSA 22.2 No. 14 (File#46510)
CE IEC 60947-6-2
H
74.4 mm
(2.93”); W
133.9 mm (5.27”);
D
74.9 mm (2.95”)
1.02 lb. (16.32 oz., 462.66 g)
#8 screws
*Note: 50Hz will increase all delay timers by 20%.
© 2016 Littelfuse Protection Relays & Controls
www.littelfuse.com/250a
Rev: 1-A-062116
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