Effect of Intense DC Electric Field on Energy Density of BOPP Films for Capacitor Applications

During operation, the energy storage dielectric inside the electromagnetic propulsion system is subjected to extremely high electric field strengths for a period of time. Current research lacks comprehensive investigation into how high electric fields influence energy storage dielectric properties. This study systematically investigates the effects of prolonged DC electric field exposure on the energy storage characteristics of biaxially oriented polypropylene (BOPP) films employed in high-field capacitor applications. Compared to untreated films, field-exposed BOPP exhibits significantly increased dielectric and conductive losses, coupled with a 42.9 % reduction in DC breakdown strength. The discharge energy density decreases from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4.62 \mathrm{J} / \text{cm}^{3}$</tex> in pure film to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.91 \mathrm{J} / \text{cm}^{3}$</tex> in treated samples. Furthermore, substantial electrode evaporation is observed in metallized films, with approximately <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{2 2. 4 \%}$</tex> of the metallized electrode surface area affected. These results and conclusions provide an important understanding of the performance degradation mechanism and failure pathway of dielectric films in pulsed power applications under extreme electric field conditions.