DLMU Series - Voltage Monitor

Littelfuse Voltage Monitoring Relays
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.


See datasheet for operation details.

Access specifications, certifications, check availability and order parts below

Catalog #Input
Voltage (V)
Termination TypeMounting MethodDimensionsWeight (lbs/g)Compare
DLMHBRAAA500-600VACScrew terminal with captive wire clamps for up to #14 AWG (2.5mm2) wireSurface mount with two #8 (M4 x 0.7) screws or snap on 35mm DIN rail4.33 x 2.95 x 1.97 in. (110 x 75 x 50mm)≅8.6oz (244g)
DLMUBLAAA200-480VACScrew terminal with captive wire clamps for up to #14 AWG (2.5mm2) wireSurface mount with two #8 (M4 x 0.7) screws or snap on 35mm DIN rail4.33 x 2.95 x 1.97 in. (110 x 75 x 50mm)≅8.6oz (244g)
DLMUBNAAN200-480VACScrew terminal with captive wire clamps for up to #14 AWG (2.5mm2) wireSurface mount with two #8 (M4 x 0.7) screws or snap on 35mm DIN rail4.33 x 2.95 x 1.97 in. (110 x 75 x 50mm)≅8.6oz (244g)
DLMUBRAAA200-480VACScrew terminal with captive wire clamps for up to #14 AWG (2.5mm2) wireSurface mount with two #8 (M4 x 0.7) screws or snap on 35mm DIN rail4.33 x 2.95 x 1.97 in. (110 x 75 x 50mm)≅8.6oz (244g)