Errors in the IEC-61000-4-7 measurement procedure for AC arc furnaces

This paper studies the analysis of typical AC arc furnace voltage and current wave procedure. In order to do so, the special behaviour of this kind of device with load fluctuations is taken into account, due to the existence of interharmonics created as a result of the fast current and voltage wave fluctuations. The FFT is used to identify harmonics and inter-harmonics and then the IEC 1000-4-7 procedure is applied to evaluate the effects of the interharmonics existence in the results, demonstrating the inaccuracy of this rule when it is used with AC arc furnaces.