Description
3-PH VOLTAGE MONITOR
Description
The DLMU Series is a universal voltage, 3-phase voltage
monitor. It continuously measures the voltage of each of the
three phases with micro-controller 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 set point and the
acceptable frequency range are fixed. Both delta and wye
systems can be monitored; no connection to neutral is required.
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 micro-controller circuitry automatically
senses the voltage range, and selects the correct operating
frequency (50 or 60Hz). The over and under voltage 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.
Reset: Reset is automatic upon correction of the voltage or
frequency fault or phase sequence
