Digital voltage and frequency relay for three-phase AC systems


The VMD421H is a powerful, all-in-one unit for monitoring three-phase AC systems up to 500 V. The VMD420 is capable of monitoring for overvoltage and undervoltage, overfrequency and underfrequency, asymmetry, phase sequence, and phase loss. Values are displayed and changed via a digital seven-segment display and menu. Values are displayed as true RMS values, and many different delays can be set.

The VMD421H unit powers itself off of the line being monitored. For the version that utilizes an external supply voltage, please see the VMD420.

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