WT3000 can carry out interharmonics testing

IEC standard 61000-4-7 Ed2, which is now obligatory as the test method for harmonics testing, specifies that the test instrument must be able to accept current input signals with a crest factor (peak current divided by RMS current) of at least four for inputs up to 5A RMS, 3.5 for inputs up to 10A RMS and 2.5 for higher RMS currents.

The Yokogawa WT3000 has its input current ranges specified in RMS, and a crest factor of three or six can be selected.

It therefore more than satisfies the accuracy requirements for testing higher harmonics according to the standard, for continuous input currents up to 33A RMS.

The WT3000 can also carry out interharmonics testing (also required by IEC 61000-4-7 Ed2) with the sample rate controlled by a phase-locked loop multiplying the input frequency by either 900 (for 50Hz) or 750 (for 60Hz).

This means that the interharmonics frequencies, which occur at 5Hz intervals, are sampled.

This so-called advanced Fast Fourier Transform (FFT) method results in an accurate and fast measurement of the interharmonics.

Yokogawa has released an updated version (5.11) of its IEC compliance software for the WT3000, which also incorporates the latest amendments to IEC standards IEC 61000-3-2 and IEC 61000-3-12 for harmonics and IEC 61000-3-3 and IEC 61000-3-11 for flicker and voltage fluctuations.