Failure analysis of dielectric of low voltage power capacitors due to related harmonic resonance effects

This paper presents an investigation on the failure of low voltage power capacitors used in the textile industry located in Thailand. The causes of the failure as well as the failure mechanisms of the dielectric used as the insulation of such capacitors are analyzed. It is found that the harmonic resonance can increase the current flowing through the capacitors. This results in extra heat, generated inside the dielectric, which exceeds the level under normal operation. Such heat results in an increase of the partial discharge inside the capacitors. This can eventually lead to the reduction of the lifetime of the capacitors.