17-9
IM DLM3054-01EN
Interharmonics (interharmonics)
If the input signal is 50 Hz in IEC harmonic measurement, a Fourier transform is taken on 10 periods of the
input signal to derive frequency components in 5-Hz resolution. As a result, the area between two harmonics is
divided into 10 frequency components. Interharmonics is the term used to refer to these intermediate frequency
components.
If the input signal is 60 Hz, a Fourier transform is taken on 12 periods of the input signal to derive frequency
components in 5-Hz resolution. As a result, the area between two harmonics is divided into 12 frequency
components.
Measurement Conditions
To analyze harmonics, use the following measurement conditions.
trigger mode
To continuously analyze harmonics while acquiring waveforms, set the trigger mode to Normal.
Time Window
Rectangle (rectangular window)
Number of Waveforms and Number of Waveform Data Points
To perform analysis in accordance with harmonic current emission standards, you must configure the instrument
so that the number of data points and the number of periods meet the following conditions.
• Number of data points
9000 points or more in 200 ms of data
• Period
50-Hz power supply (45 Hz to 55 Hz): 10 periods of data
60-Hz power supply (55 Hz to 65 Hz): 12 periods of data
Probe Setup (ProbeSetup)
The channel selection, probe attenuation, voltage-to-current conversion ratio, and deskew settings are the same
as those for the switching loss analysis feature.
Analysis Start Point (Start Point)
Set the analysis start point.
Power Supply Voltage of the EUT (System Voltage)
Set the power supply voltage of the device that you want to perform harmonic analysis on. The instrument uses
the power supply voltage to determine the harmonic limits set by the harmonic current emission standard and
uses the limits as references (see below for more information). The default setting is 230 V.
Selectable range: 90 V to 440 V
Resolution: 1 V
The harmonic current emission standard lists the limits for each harmonic when the (single-phase) power
supply voltage is 220 V, 230 V, or 240 V. The limits for other power supply voltages must be determined through
conversion. When the power supply voltage is outside of the range of 220 to 240 V, the instrument’s power
supply analysis feature uses the following equation to determine the limits for each class.
Converted limit = Limit for each class × 230/Equipment power supply voltage
Setting the Applicable Class (Class Setup)
Configure class-related settings.
Class (Class)
Sets the applicable class to A, B, C, or D.
17 Power Supply Analysis Feature (Power Analysis and Power Measurement, Option)