Critical Parameters of Metallized Film Capacitor’s Failure

During metallized film capacitors (MFCs) operation in high electric field modes, when operating voltage is in 3 – 5 times higher than its nominal value, there is a deterioration of their performance due to self-healing processes. Usual parameter for performance evaluation is relative capacitance changing. In the same time another capacitor’s parameters, such as dissipation factor and equivalent parallel resistance are rarely used for this purpose. Dependencies of capacitor’s parameters on accumulated self-healing energy (a sum of all previous self-healing act energies) are presented. It was found that MFC’s failure in high electric field modes is associated with equivalent parallel resistance decreasing. The relationship between critical value of accumulated self-healing energy and equivalent parallel resistance was obtained.

I. Introduction

Metallized film capacitors (MFCs) are widely used in modern electric equipment. Distinctive feature of this capacitor’s type is self-healing (SH) ability, i.e., restoring its operational voltage after sudden dielectric breakdown. Due to this ability, MFCs have high operational electric field strength and high reliability [1 – 5] .