Voltage
Monitor
Controls Switching of a Transfer Panel:
A three phase line monitor constantly reads the voltages on
the three phase lines. When a power interruption, low voltage, phase
unbalance or phase loss event occurs, the line monitor can switch the
supply voltage to a backup source. In the drawing, the Utility Power
Switch is held closed by the WVM Series whenever the three phase voltages
are within acceptable limits. The trip delay in the WVM Series allows it
to ignore momentary glitches in the utility’s power. If a voltage fault
occurs, the WVM’s contacts revert to the state shown in the diagram. The
Utility Power Switch is disconnected and the backup power start circuitry
is energized. When backup power is established the backup power switch is
energized and power is re-established in the building. The WVM Series is
an excellent choice for this application because it includes a restart
delay that allows the backup power supply to continue to operate until the
utilities power has been re-established for an acceptable period of time.
At the end of the delay, the WVM’s internal contacts transfer returning
the building to utility power. The WVM also includes a 10 fault memory
that remembers and displays the last 10 fault events on an LED status
panel.
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