6-7
IM WT310E-01EN
Harmonic Measurement (Option)
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App
Index
Note
• If the fundamental frequency of the PLL source cannot be measured due to fluctuations or distortion,
correct measurement results cannot be obtained. We suggest that you set the PLL source to the voltage,
which has relatively smaller distortion than the current.
• If the fundamental frequency is 200 Hz or less and high frequency components are present, we suggest
that you turn on the frequency filter (500 Hz cutoff frequency).
• If the amplitude of the PLL source input signal is small compared to the rated range, PLL synchronization
may fail. Change the measurement range so that the amplitude level of the PLL source is 50% or higher
than the rated range (100% or higher if the crest factor is set to 6 or 6A).
Measured Harmonic Order
You can set the upper limit of measured harmonic order in the range of 2 to 50. However, the range
varies depending on the fundamental (1st harmonic) frequency. This is because the upper limit of
harmonics that are computed varies depending on the fundamental frequency. The default value is 50.
Example
• Up to 50 when the fundamental frequency is 50 Hz
• Up to 4 when the fundamental frequency is 1.2 kHz
Note
• When a harmonic order exceeding the upper limit is specified, display B shows hyphens (-----).
• For details on the upper limit of measured harmonic order, see section 7.3 in the Getting Started Guide,
IM WT310E-02EN.
THD equation
Select the THD equation from below. The default value is iEC.
The following explanation is for when the upper limit of measured harmonic order is 50. If the upper
limit is less than 50, computation is performed to the upper limit.
• iEC: Computes the ratio of the rms value of the 2nd to 50th harmonic component to that of the
fundamental (1st order).
• CSA: Computes the ratio of the rms value of the 2nd to 50th harmonic component to that of the rms
value of the 1st to 50th component.
Equation
iEC
/
C
1
n
k=2
(C
k
)
2
×100
CSA
/
n
k=2
(C
k
)
2
n
k=1
(C
k
)
2
×100
• C
1
: Fundamental (1st harmonic) component
• C
k
: Fundamental or harmonic component
• k: Measured harmonic order
• n: Upper limit of measured harmonic order. This value varies depending on the fundamental
frequency of the PLL source.
6.3 Setting the PLL Source, Measured Harmonic Order, and THD Equation
