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.