Effect of supply network harmonics to frequency converter intermediate circuit capacitor temperatures

Uncertainties in measurement due to varying environmental conditions make the benchmarking of frequency converter's intermediate circuit capacitors difficult. The effect of changes in supply network quality, especially the changes in harmonic distortion, to capacitor's temperature-rise is analyzed. The capacitor lifetime is as a function of its temperature and thus more precise measurements and knowledge of the dependencies will lead to a more cost-efficient and reliable design. According to the tests all studied supply network parameters and unidealities in temperature measurement affect clearly the results. All discussed properties must be known if a test is to be repeated under the same conditions. An unexpected finding in the tests was that high frequency supply voltage distortion decreases capacitor temperature and thus extends its lifetime.