The multi-functional voltage relays of the VMD420 series are designed to monitor the frequency, undervoltage and overvoltage and the voltage between two threshold values (window discriminator function) in 3(N)AC systems. The voltages are measured as r.m.s. values. The currently measured value is continuously shown on the LC display. The measured value leading to the activation of the alarm relays will be stored. Due to adjustable response times, installation-specific characteristics, such as device-specific start-up procedures, short-time voltage fluctuations, etc. can be considered . Device version VMD420 requires an external supply voltage.

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  • Undervoltage, overvoltage and frequency monitoring in 3(N)AC systems 0…500 V
  • Asymmetry, phase failure and phase sequence monitoring
  • Different monitoring functions selectable
    < U, > U, < f, > f
  • Start-up delay, response delay, delay on release
  • Adjustable switching hysteresis
  • r.m.s. value measurement (AC)
  • Digital measured value display via multi-functional LC display
  • Preset function (automatic assignment of basic parameters)
  • LEDs: Power On, Alarm 1, Alarm 2
  • Measured value memory for operating value
  • Continuous self monitoring
  • Internal test/reset button
  • Two separate alarm relays (one changeover contact each)
  • N/C or N/O operation and fault memory behaviour selectable
  • Password protection for device setting
  • Sealable transparent cover
  • Two-module enclosure (36 mm)
  • Indication of the system frequency
  • RoHS-compliant
  • Monitoring of voltage-sensitive machines and electrical installations
  • Switching on and switching off at a certain voltage level
  • Monitoring of stand-by and emergency supply systems
  • Supply voltage monitoring of portable loads
  • Protection of three-phase motors against phase failure and
  • Transformer protection, asymmetrical load can be recognized


Optional accessories for LINETRAXX® VMD420

TypeArt No.
Mounting clip for screw fixing (1 piece per device)B98060008

Variants of LINETRAXX® VMD420

TypeSupply voltage US*Nominal system voltage Un*Art. No.**
VMD420-D-1AC 16…72 V / DC 9,6…94 V, 15…460 Hz3(N)AC 0…500 V / 288 V 15…460 HzB73010005
VMD420-D-2AC/DC 70…300 V, 15…460 Hz3(N)AC 0…500 V / 288 V, 15…460 HzB73010006
* absolute values
**(B7… = push-wire terminal / B9… = screw-type terminal)

Downloads for LINETRAXX® VMD420



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