9-6 IM02601001E www.eaton.com
Functions on the Web Server Pages
From the Power page, click one of the radio buttons on the left side of the page that rep-
resents the type of power measurement you want to view. The page will update to display
a graph with minimum, maximum and average values as per the selection.
Power Factor (Apparent)
The page contains information about the present power quality for PXM2260 and
2270 meters. These meters calculate the following instantaneous values, averaged over
a period of 60 cycles:
Percent THD of Current for Phases A, B, and C•
Percent THD of Voltage for Phases A, B, and C.•
Using the drop-down box above the graph, you can select to view this information as a
trend, with minimum and maximum values, or as harmonics.
The PXM2250 meter does not measure %THD.
THD
The Total Harmonic Distortion (THD) is the ratio, expressed as a percentage, of the rms
value of the ac signal after the fundamental component is removed and inter-harmonic
components are ignored to the rms value of the fundamental. The formula for THD is
provided below. The variables X
1
and x
n
may represent either voltage or current and may
be expressed either as rms or peak values, as long as all are expressed in the same
fashion.
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