Protection Relays
Voltage Monitoring Relays
DLMU SERIES
Description
The DLMU Series is a universal voltage, 3-phase voltage
monitor. It continuously measures the voltage of each of the
three phases with microcontroller accuracy and compares the
value to preset trip points. It separately senses phase reversal
and loss; over, under and unbalanced voltages; and over or
under frequency. Protection is assured during periods of large
average voltage fluctuations or when regenerated voltages
are present. The unit trips within 200ms when phase loss
is detected. Adjustable time delays are included to prevent
nuisance tripping and short cycling of sensitive equipment.
The isolated, 10A, SPDT and 2A alarm output relay contacts
trip when a phase voltage exceeds the trip limits for the trip
delay. Nominal line voltage, voltage unbalance, and time
delays are knob adjustable. The phase loss setpoint and the
acceptable frequency range are fixed. Both delta and wye
systems can be monitored; no connection to neutral is required.
Wiring Diagram
L1, L2, L3 = Line Voltage Input
NO = Normally Open Contact
NC = Normally Closed Contact
C = Common,Transfer Contact
!
Operation
Upon application of line voltage, the output is de-energized
and the restart delay begins. If all the 3-phase voltages are
within the acceptable range, the output energizes at the end
of the restart delay. The microcontroller circuitry automatically
senses the voltage range, and selects the correct operating
frequency (50 or 60Hz). The over and undervoltage trip points
are set automatically. When the measured value of any phase
voltage exceeds the acceptable range limits (lower or upper)
the trip delay begins. At the end of the trip delay the output
relay de-energizes. If the phase voltage returns to an acceptable
value before the trip delay expires, the trip delay is reset and the
output remains energized. Under, over, and unbalanced voltages
plus over or under frequency must be sensed for the complete
trip delay before the unit trips. The unit trips in 200ms when
phase loss or reversal are sensed. The unit will not energize if a
fault is sensed as the line voltage is applied.
CAUTION: 2 amp max. fast acting fuses are
recommended to protect the equipment‘s wiring.
They are not required to protect the DLMU.
! = Select alarm contact connection as N.O. or N.C. when ordering;
N.O. Shown.
Features & Benefits
FEATURES
BENEFITS
Proprietary
microcontroller
based circuitry
Constant monitoring to protect against phase loss,
phase reversal, over voltage, under voltage,
unbalance, short cycling and over/under frequency
Universal line
voltage range
Flexibility to work in 200 to 480VAC or 500 to
600VAC applications
Reset: Reset is automatic upon correction of the voltage or
frequency fault or phase sequence.
DIN rail (35mm) or
surface mounting
Installation flexibility
Provides diagnostics of relay, fault and time
delay status
LED indication
User adjustable
time delays
Prevents nuisance tripping and short cycling of
sensitive equipment
Ordering Information
MODEL
LINE VOLTAGE
OUTPUT
RESTART FUNCTION
Staggered restart
Lockout, min off time
No restart delay
VOLTAGE UNBALANCE
Adjustable 2 - 10%
Adjustable 2 - 10%
Adjustable 2 - 10%
Adjustable 2 - 10%
TRIP DELAY
RESTART DELAY
Adjustable 0.6 - 300S
Adjustable 0.6 - 300S
None
DLMHBRAAA
DLMUBLAAA
500 to 600VAC SPDT & NO
200 to 480VAC SPDT & NO
Adjustable 1 - 30s
Adjustable 1 - 30s
Adjustable 1 - 30s
Adjustable 1 - 30s
DLMUBNAAN 200 to 480VAC SPDT & NO
DLMUBRAAA 200 to 480VAC SPDT & NO
Staggered restart
Adjustable 0.6 - 300S
If you don’t find the part you need, call us for a custom product 800-843-8848
© 2016 Littelfuse Protection Relays & Controls
www.littelfuse.com/dlmu
Rev: 1-A-062716
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