Observations in Strain Sensing of Metallized Film Capacitors for AC filtering during Degradation

This paper investigates the aging and failure phenomena of metallized film capacitors (MFCs) for AC filtering based on strain sensing. A strain sensing-based health indicator of capacitors has recently been reported with the advantages of being non-invasive, having high sensitivity to degradation, and less susceptible to interference. This discovery provides new opportunities for degradation analysis of MFCs. The strain sensing results of MFCs are collected by an accelerated aging platform in this paper. The testing results of AECs and MFCs in strain sensing are different due to different degradation mechanisms. During the aging stage, there is almost no physical deformation for AC film capacitor. Close to the moment of failure, the strain sensing resistance of the MFC changes significantly due to the deformation caused by the cauterization of the dielectric film. Meanwhile, the case temperature change of MFCs at the moment of failure is insignificant compared to strain sensing. The observation results of MFCs give a new perspective on the fault diagnosis and condition monitoring of this type of capacitor.