2-8
IM 760201-01E
Elements
Element refers to a set of input terminals that can receive a single phase of voltage
and current to be measured. The WT500 can contain up to three elements, numbered
from 1 to 3. The element number follows the function symbols discussed in “Input
Element Harmonic Measurement Functions” earlier in this section. For example, “U1(2)”
corresponds to the voltage of the second harmonic of element 1.
Wiring Systems
The selectable wiring system patterns vary depending on the number of input elements
that are installed in the WT500.
Wiring Unit
The wiring unit is a set of two or three input elements of the same wiring system that
are grouped to measure three-phase power. The wiring unit is represented by
Σ
. The
measurement function of a wiring unit is called a
Σ
function.
For example, “U
Σ
(1)” corresponds to the average of the fundamental voltages of the
input elements that are assigned to the wiring unit.
PLL Source (See section 6.3 for operating instructions)
To measure harmonics, the fundamental period (the period of the fundamental
signal) that will be used to analyze the harmonics must be determined. The signal for
determining the fundamental period is the PLL (phase locked loop) source. For stable
harmonic measurement, choose an input signal for the PLL source that has as little
distortion and fluctuation as possible. The ideal signal when the crest factor is set to 3
(see section 5.11 for details) is a rectangular wave with an amplitude that is 50% or more
of the measurement range (see section 1.3 for details). When the crest factor is set to
6, the ideal signal is a rectangular wave with an amplitude that is 100% or more of the
measurement range.
Also, applying a clock signal (Ext Clk) with the same period as the waveform whose
harmonics are being measured makes stable harmonic measurement possible.
2.2 Measurement Functions and Periods
