Power meter complies with latest obligatory EN standards on harmonics testing
07 May 2009
The Yokogawa WT3000 digital power analyser equipped with IEC harmonics testing software complies with the latest EN standard on harmonics testing: EN61000-3-2:2006. IEC Standard 61000-4-7 Ed. 2, 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 4 for inputs up to 5 A RMS, 3.5 for inputs up to 10 A RMS and 2.5 for higher RMS currents.
Unlike other instruments, the Yokogawa WT3000 has its input current ranges specified in RMS, and a crest factor of 3 or 6 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 33 A 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 50 Hz) or 750 (for 60 Hz). This means that the interharmonics frequencies, which occur at 5 Hz intervals, are sampled. This so-called advanced FFT (Fast Fourier Transform) method results in an accurate and very 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.
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