High energy density capacitor dielectric mismatch and aging characteristics

The aging characteristics of two high energy density capacitor dielectric films, polypropylene and polyvinylidene fluoride, with transformer oil and glycerine as dielectric fluids, were obtained using the step-stress test. The inverse power law was used in the analysis of the experimental data. With the value of power exponent determined from the step-stress for each dielectric film/fluid combination, an equivalent constant stress lifetime was estimated for the two configurations tested, with and without a void in the middle layer. The results show that lifetime was longer for the matching dielectric film/fluid combination. Also, the lifetime and the breakdown strength ratio was significantly reduced for the dielectric film/fluid mismatch, especially in the presence of a void