9-2
IM WT3001E-51EN
In IEC harmonic measurement, this instrument performs Fourier transform on the input
signal and divides the signal into frequency components as follows:
• Interharmonics
If the input signal is 50 Hz, 10 periods of the waveform are divided in 5-Hz resolution.
Thus, the section between each harmonic order is divided into 10 sections. The
components between each harmonic order are called interharmonics.
100
150
Interharmonics
Rms component
Frequency [Hz]
50
100
150
200
250
dc
2
nd
harmonic 3
rd
harmonic 4
th
harmonic 5
th
harmonic
Fundamental
2
nd
harmonic
3
rd
harmonic
When the fundamental signal is 50 Hz
If the input signal is 60 Hz, 12 periods of the waveform are divided in 5-Hz resolution.
Thus, the section between each harmonic order is divided into 12 sections.
Rms component
Frequency [Hz]
60
120
180
240
dc
2
nd
harmonic
3
rd
harmonic
4
th
harmonic
Fundamental
When the fundamental signal is 60 Hz
9.1 IEC Harmonic Measurement Function
