Influence of electrode area on dielectric breakdown strength of thin poly(ethylene terephthalate) films [power capacitor applications]

DC breakdown voltages of 8-20 μm thick poly(ethylene terephthalate) (PET) films were measured as a function of electrode area. The area of the measurement electrodes were between 0.045-9.3 cm². Also 13-15 m² capacitor elements were tested. Weibull distribution parameters, scale parameter α and shape parameter β, were fitted to the obtained breakdown strength data. Based on the small area results, short term breakdown strength of large area capacitor elements was predicted. Area extrapolation based on the scale parameter α was compared with Weibull extrapolation, in which also the shape of the distribution is taken into account. It was concluded that the Weibull extrapolation better represented the large area breakdown strength than the area extrapolation.