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8.2 Setting the Element, PLL Source and Harmonic Distortion Method
Explanation
8-4
Setting the Element
Only one input element should be set for harmonic analysis. The initial value is EL1. At the
WT110 the element setting menu does not appear.
• EL1 : Element 1 will be used for analysis;
• EL2 : Element 2 will be used for analysis; In case of the 253502, this menu will not be shown;
• EL3 : Element 3 will be used for analysis.
Setting the PLL source
For harmonic analysis, it is necessary to select the input to be used as the fundamental
frequency (PLL source) for synchronization. (PLL stands for Phase Locked Loop.)
• V1: Sets the voltage of element 1 as the PLL source;
• A1: Sets the current of element 1 as the PLL source;
• V2: Sets the voltage of element 2 as the PLL source;
• A2: Sets the current of element 2 as the PLL source;
• V3: Sets the voltage of element 3 as the PLL source;
• A3: Sets the current of element 3 as the PLL source.
Note
• If the fundamental frequency of the PLL source cannot be measured due to fluctuations or distortion, it is
not possible to obtain correct measurement results. In this case, it is suggested that voltage with
relatively small distortion be selected as the PLL source.
• It is recommended to turn ON the filter in cases where the fundamental frequency is 300Hz or less and
high frequency components are present.
• If the amplitude of the input signal selected as the PLL source is smaller than the rated range value, PLL
synchronization may sometimes fail. In this case, it is suggested that a suitable measurement range be
selected so that the input level exceeds 30% of the rated range value.
Setting the Computation Method of Harmonic Distortion
The computation method of harmonic distortion can be selected from the following two. In the
following explanation a maximum of 50 analysis orders is assumed. In case of a maximum less
than 50, computation/display will be performed up to that order.
• iEC : Computes the ratio of the rms value of the 2nd to 50th order component to that of the
fundamental (1st order).
• CSA : Computes the ratio of the rms value of the 2nd to 50th order component to that of the
rms value of the 1st to 50th component.
Computation Equation
In case of iEC
n
/
2
(C
)
C
1
k
k=2
In case of CSA
n
n
/
2
(C
)
k
k=2
k=1
C1 : Fundamental component (1st order)
Ck : Fundamental or harmonic component
k
: Analysis order
n
: Maximum order. The maximum order depends on the fundamental frequency of the input set
as the PLL source. Refer to Ch. 15 for more details.
2
(C
)
k
IM 253401-01E
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