3-10
Volt-Amps and Volt-Amps Reactive
Refer to the single-phase volt-amps and
volt-amps reactive section of this document
for definitions of these parameters.
The 1040C has a provision for displaying
and modifying both volt-amps and vars;
successively pressing the "Power" key during
operation will first display watts, then vars,
then volt-amps. The user can continue
indefinitely to scroll through these three
choices.
Some points of interest regarding va and
var measurements:
It is important to note that unless there is a
phase angle of greater than zero between
voltage and current, the var value will be zero.
Also, since va and var indications are sub-
functions of the power mode, adjustment of
these values using direct entry, the control
knob, or the up/down keys affects the value by
changing only the current, not the voltage or
the phase angle. The current can only be
modified to a point within the current range of
the 1040C. If the necessary current exceeds
this range, the display will indicate "Entry
Error". Additionally, if the phase angle is set
to zero and the user attempts to enter any var
value other than zero, "Entry Error" will be
indicated. This is because under these
conditions, no value of voltage or current will
produce anything other than zero vars.
Typical applications of va and var meters
or transducers for multi-phase systems
involve circuit connections which are similar,
if not identical to those employed by multi-
phase watt and power factor meters and
transducers. Therefore, representative circuit
connections and calibration connections for
these devices are shown in figures 9 and 10,
respectively. When connected per the
calibration setup diagram, calibration of these
instruments can be performed in accordance
with the meter manufacturer's
recommendations. For more detailed
instructions on operating the 1040C in the
volt-amps and volt-amps reactive modes, refer
to section 2.5.6 of the operation manual.
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