3 PHASE MONITORS
PHONE (614) 889-6152
TECH. ASSISTANCE (614) 876-8308
FAX # (614) 876-8538
4970 Scioto Darby Rd.Hilliard, Ohio 43026
Div. Morlan & Associates, Inc. WWW.FLEX-CORE.COM
sales@flex-core.com
161
3 PHASE MONITORS
3 PHASE MONITOR MODEL 257
The Model 257 continuously monitors 3-phase power lines for
abnormal conditions. When properly adjusted, the Model 257
willdetectphaseloss ona loadedmotor evenwhenregenerated
voltage is present.This device consists of a solid-state voltage
and phase-angle sensing circuit, driving an electro-mechanical
relay.When correct voltage and phase rotation are applied, the
internal relay will energize.A fault condition will de-energize the
relay.When the fault is corrected, the monitor will automatically
reset. (A manual version is also available)
TheModel257 doesnotrequire a neutral connection and can
be used with Wye or Delta
systems. Voltage ranges are
sufficiently wide to allow for
proper adjustment to existing
conditions. Both TRIP and
NORM condition indicators are
provided to aid in adjustment
and system trouble-shooting.
Typical Application
Detects Phase Loss, Low Voltage, Phase Reversal
50Hz, 60Hz, and 400Hz Models
Automatic or Manual Reset
3 PHASE MONITOR
All Dimensions In Inches
**Order 8-Pin Socket Number 51X120 (UL Listing E126447)
Smart Socket Available for 480 to 635Vac Circuits
Mountthe8-pinsocketina suitableenclosure.ANEMA-1rated
enclosure, designed for socket-mounted relays is available
uponrequest.Connect3-phase powerto terminals3, 4, and5
on the socket.Phase rotation should be verified.Connect the
load control wiring to the appropriate terminals on the socket:
Motor Control Application...............Use terminals 1 and 8
Phase Loss Alarm Applications......Use terminals 1 and 2
Insert the Model 257 into the socket and apply power. If the
contact does not transfer (green light ON), check that all
phases are present, and of the correct voltage. If power is
correct, rotate the level adjustment counter-clockwise. If the
contactstill doesnottransfer,removepowerand reversetwoof
the three phase wires at the socket (phase rotation reversed).
Re-apply power.The contact should transfer to provide a signal
path between pins 1 and 8.
ADJUSTMENT SETTING
Thefollowingprocedure willallowtheModel 257tobe adjusted
to achieve a trip point just below the nominal phase-to-phase
voltage, where the unit is applied.
Rotate the adjustment control fully clockwise, or until the red
(TRIP) indicator illuminates. Slowly rotate the adjustment
control in a counter-clockwise direction, just until the green
(NORM) indicator illuminates. At this point, the Model 257 is
themostsensitivetoirregular powerlineconditions.If nuisance
tripping occurs, turn the control slightly further counter-
clockwise. A more accurate setting will require the use of a
3-phase variac to lower the voltage to an exact measurable
setting.A factory set version of all models and voltage ranges
are available.(Consult factory for details.)
TROUBLESHOOTING
Should the Model 257 fail to operate properly, check that all
three voltages are present, and are of the correct voltage
level and phase rotation. Check all fuses and verify that all
wiring connectionsare correct.If problemspersist,consult the
factory for assistance.
MANUAL RESET VERSIONS
If you do not wish to use the external reset switch on the
manual reset version, you must jumper pins 6 and 7.Refer to
the manual reset 8-pin diagram.
14
85
2
REMO
RESET
3OA
76
14
85
23
76
OB
OC
OA
OB
OC
DIMENSIONS
Automatic Reset Manual Reset
®
DESCRIPTION INSTALLATION
SPECIFICATIONS MODEL 257
DIMENSIONS PIN DESIGNATIONS
AUTO Reset B257B 257B A257B EX257B B257B-400 257B-400
Manual Reset B257BM 257BM A257BM WX257BM B257BM-400 257BM-400
Nominal AC Voltage
Phase-to-Phase 120VAC 208/240VAC 480VAC 380VAC 120VAC 208/240VAC
Case Color Gray Red Yellow Yellow Gray Red
Adjustment Range 85-
120VAC 160-
240VAC 380-
480VAC 300-
400VAC 85-120VAC 160-240VAC
Frequency 60Hz 60Hz 60Hz 50Hz 400Hz 400Hz
Power Consumption 1.4W 2.4W 3.7W 3.0W 1.4W 2.4W
Transient Protection 2500VAC for 10msec
Repeat Accuracy +0.1% of set point (fixed conditions)
Response Time 50msec (set or reset)
Dead Band Approximately 2%
Output Contacts SPDT 10 Amps at 240VAC
Expected Relay Life Mechanical: 10 Million Operations
Electrical: 100,000 Operations at rated load
Operating Temp. -20°F to +131°F
Humidity Tolerance 0-97% w/o condensation
Enclosure Material Dust Cover: ABS Plastic
Header: Nylon
Mounting 8-Pin Socket (**Sold separately)
Weight 5 ounces
Agency Approvals
UL Recognized* and CSA Certified
*Conditions of acceptability:
(1) The 380V and 480V versions must be used with a UL Recognized 600Vac socket
(2) For use in a Pollution Degree 2 Environment
(3) To Be Installed on the load side of branch circuit protection rated 10A.
E60400
FEATURES
