DLM Series - Voltage Monitor

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Littelfuse products are not designed for, and shall not be used for, any purpose (including, without limitation, automotive, military, aerospace, medical, life-saving, life-sustaining or nuclear facility applications, devices intended for surgical implant into the body, or any other application in which the failure or lack of desired operation of the product may result in personal injury, death, or property damage) other than those expressly set forth in applicable Littelfuse product documentation. Warranties granted by Littelfuse shall be deemed void for products used for any purpose not expressly set forth in applicable Littelfuse documentation. Littelfuse shall not be liable for any claims or damages arising out of products used in applications not expressly intended by Littelfuse as set forth in applicable Littelfuse documentation. The sale and use of Littelfuse products is subject to Littelfuse Terms and Conditions of Sale, unless otherwise agreed by Littelfuse. "Littelfuse" includes Littelfuse, Inc., and all of its affiliate entities.

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)HumidityInput AC Line Frequency (Hz)Input Phase SequenceInput TypeInput Voltage Maximum (V)Isolation Voltage (V)Output Load Rating (VA)Output TypeOver/Under Frequency (%)Overvoltage Reset Voltage (%)StockCompare
DLMHBRAAA500 - 600 VacScrew terminal with captive wire clamps for up to #14 AWG (2.5 mm²) wireSurface mount with two #8 (M4 x 0.7) screws or snap on 35mm DIN rail4.33 H x 2.95 W x 1.97 D in. (110 x 75 x 50 mm)0 Kg95% non-condensing50 / 60A; B; C; L1; L2; L33-phase delta or WYE with no connection to neutral600≥2500 Vrms input to output10 A resistive @ 240 Vac; 8 A resistive @ 277 Vac; NO-1/4 hp @ 120 Vac; 1/3 hp @ 240 VacIsolated electromechanical relay±4%; Reset ±3%; 50 / 60 Hz≅-3% of the trip voltageCheck
DLMUBLAAA200 - 480 VacScrew terminal with captive wire clamps for up to #14 AWG (2.5 mm²) wireSurface mount with two #8 (M4 x 0.7) screws or snap on 35mm DIN rail4.33 H x 2.95 W x 1.97 D in. (110 x 75 x 50 mm)0 Kg95% non-condensing240 V ac: 50/60; 380 V ac: 50; 480 V ac: 60A; B; C; L1; L2; L33-phase delta or WYE with no connection to neutral550≥2500 Vrms input to output10 A resistive @ 240 Vac; 8 A resistive @ 277 Vac; NO-1/4 hp @ 120 Vac; 1/3 hp @ 240 VacIsolated electromechanical relay±4%; Reset ±3%; 50 / 60 Hz≅-3% of the trip voltageCheck
DLMUBNAAN200 - 480 VacScrew terminal with captive wire clamps for up to #14 AWG (2.5 mm²) wireSurface mount with two #8 (M4 x 0.7) screws or snap on 35mm DIN rail4.33 H x 2.95 W x 1.97 D in. (110 x 75 x 50 mm)0 Kg95% non-condensing240 V ac: 50/60; 380 V ac: 50; 480 V ac: 60A; B; C; L1; L2; L33-phase delta or WYE with no connection to neutral550≥2500 Vrms input to output10 A resistive @ 240 Vac; 8 A resistive @ 277 Vac; NO-1/4 hp @ 120 Vac; 1/3 hp @ 240 VacIsolated electromechanical relay±4%; Reset ±3%; 50 / 60 Hz≅-3% of the trip voltageCheck
DLMUBRAAA200 - 480 VacScrew terminal with captive wire clamps for up to #14 AWG (2.5 mm²) wireSurface mount with two #8 (M4 x 0.7) screws or snap on 35mm DIN rail4.33 H x 2.95 W x 1.97 D in. (110 x 75 x 50 mm)0 Kg95% non-condensing240 V ac: 50/60; 380 V ac: 50; 480 V ac: 60A; B; C; L1; L2; L33-phase delta or WYE with no connection to neutral550≥2500 Vrms input to output10 A resistive @ 240 Vac; 8 A resistive @ 277 Vac; NO-1/4 hp @ 120 Vac; 1/3 hp @ 240 VacIsolated electromechanical relay±4%; Reset ±3%; 50 / 60 Hz≅-3% of the trip voltageCheck
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