Weibull statistical analysis of area effect on the breakdown strength in polymer films

The area and film thickness effects on the breakdown strength were examined for different polymer films at room temperature. Electrodes of four different diameters were used for this experimental work, which were in the range of 1/2 to 2 inches in diameter. Materials of various thickness used for this investigation were aramid paper (NOMEX type 410), Polyimide film (KAPTON), Mylar Polyester film, and Nomex-Polyester-Nomex composites. Two-parameter Weibull distribution has been used to analyze the results. The experimental analysis shows that the breakdown strength decreases as the electrode area increases. In case of thickness of 125 μm film, change of 10-12% in the breakdown strength was observed, where as for 25 μm thickness, 30-35% change in the breakdown strength was noticed. It was also noticed that the 25 μm thickness films are more exposed to the mechanical damage during handling process, thus chances of lower breakdown strength of such films are more, as probability of covering the mechanically damaged area increases with the increase in the electrode area.