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Harmonic Measurements in PSM
The consumption data log can record the average THD-F of each phase of voltage and each phase of
current for each logging period. The summary values at the top of the screen are the average of all the
values shown on the screen.
When viewing a consumption waveform, transforming it into a harmonic graph presents a bar chart
showing the relative magnitude of each of the first 50 harmonics. The THD-F is listed at the lower right.
Transforming a consumption waveform into harmonic data presents a chart of the magnitudes and
phase angles of each harmonic. The THD-F and K factor are also listed.
The measurements of voltage presented on the ATPOL II can also be displayed in PSM by using the
remote control feature.
In addition our Report Generator software will present average THD-F for voltage and current of each
phase during any one or two intervals of time set by the user. If the use of two time intervals is chosen,
it will report the percent change and the actual change between the two intervals. For instance, if a
comparison report is chosen and THD-F of V
1N
is 4.8% during the first interval and 4.7% during the
second interval, then the report would show:
Before After Units Change
%
Change
THD, Voltage, Phase 1
4.8
4.7
%
-0.01
-2.1%
Swells (Surges) and Inrush Measurements
Voltages and currents may grow suddenly due to temporary or switched conditions in the load or supply
of power. Examples of this occurring are a current inrush when a motor is first turned on, a swell in
voltage when the power source is switched from a weak source to a stronger one or when a large load
is suddenly taken off-line.
In each of these conditions, the waveform remains basically the same as it was before, but the
amplitude (or scale) of the waveform has grown. Since it is still a periodic waveform, it makes great
sense to measure it in RMS. This allows for simple comparison to the voltage or current levels before
and after the swell has occurred. For this reason, swells and inrush are measured in RMS. For highest
accuracy, ATPOL II calculates the RMS of each ½ cycle of each voltage and current input in order to
detect even the smallest swells and inrush. In this way, no swells or inrushes are missed.
Dips (Sags) Measurement
Voltages and currents may shrink suddenly due to temporary or switched conditions in the load or
supply of power. Examples of this occurring are a current dropout when a motor is suddenly turned off,
a dip in voltage when the power source is switched from a strong source to a weaker one or when a
large load is suddenly put on-line.
In each of these conditions, the waveform remains basically the same as it was before, but the
amplitude (or scale) of the waveform has shrunk. Since it is still a periodic waveform, it makes great
sense to measure it in RMS. This allows for simple comparison to the voltage or current levels before
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