ABSTRACT
Cycloconverters are a major source of interharmonics. Large mill motor drives using cycloconverters ranging up to 8 MVA appeared in 1970s. Electrical arc furnaces are another major source. Arcing devices give rise to interharmonics. These include arc welders. Practically, the ideal conditions of operation are not obtained, which give rise to non-characteristics harmonics and interharmonics. The interharmonics can originate from the converters by interaction of a harmonic from the dc link into the power source. Certain relationship exists between the converter pulse numbers, the harmonic frequencies present in the output voltage, and the input current. The furnace is generally operated with static var compensation systems and passive shunt harmonic filters. The installations can compensate rapidly changing reactive power demand, arrest voltage fluctuations, reduce flicker and harmonics, and simultaneously improve the power factor to unity. The interharmonic frequency components, greater than the power frequency, produce heating effects, similar to those produced by harmonics.
