Measurement Computing WavePort 312P rev.1.0 - Manual (Page 52)

5-4 Phaser Diagram PowerVista/312 User’s Manual
5.3.2 Total vs. Displacement Power Factor
The Phasor Demand Window displays all fundamental phasor and total RMS demand quantities. Of interest for
this application note is the viewing of power factors and understanding their use.
The power factor listed beneath RMS results is the Total Power Factor. This power factor is defined as the
cosine of the arc-tangent of the RMS Vars divided by the RMS Watts. Since both RMS power quantities by
definition are point-by-point on wave, they include all higher frequency energy, as high as the system has
adequately digitized. For EasyPower Measure, this includes the fundamental frequency to the 50
th harmonic.
The power factor listed beneath Fundamental results is the Displacement Power Factor. This power factor is
defined as the cosine of the angle of displacement between voltage and current vectors. Thus, Displacement
Power Factor by definition only includes the fundamental energy in the system.
From the above definitions, the magnitude of the Total Power Factor will thus always be less than or equal to the
Displacement Power Factor. If there is no harmonic energy, they are equal. For all other conditions, Total
Power Factor is less than Displacement Power Factor. Harmonic currents are highly reactive in nature and will
almost always cause a reduction Total Power Factor.
5.3.3 Harmonics Tabulation
The integer harmonic result tabulation in the Phasor Harmonics Window is a complete 1 st to 50 th harmonic
decomposition plus THD of a single cycle (the one displayed) for all signals measured. All magnitudes and
angles for all signals of course will not fit within the display area, so the user is allowed to choose columns as
defined in the Phasor Diagram Configuration. Several toolbar buttons can be used to move quickly through all
display options.
Toggle Engineering vs. Percent in Harmonic Tabulation
Cycle Forward Through Harmonics Tabulation Column Options.
Cycle Backward Through Harmonics Tabulation Column Options.
Since we are decomposing a 128 point single cycle, only integer harmonics can be calculated. For display of
non-integer frequencies refer to Detailed Harmonics.
As a verification to the accuracy of calculation, two quick checks can be used. The Phasor Demand Window
displays phasors for fundamental frequencies as well as any harmonic phasors. The calculation used in the
demand calculations is a single frequency Fourier multiplication technique, different from the FFT routine used
in the harmonic decomposition. The decomposed fundamental in the harmonics tabulation should (and will)
match the fundamental phasor magnitude in the demand tabulation. This will also hold for the decomposed
harmonic voltage and the harmonic phasor tabulated in the demand data when harmonic phasors are being
viewed. The harmonic display selection in the Phasor Diagram Configuration should not be set for percent, but
for viewing Volts and Amps, to make these comparisons.