Investigation of the Breakdown Testing Method for Bopp Films Under Interlayer Pressure

New energy power systems, high-performance electric vehicles, energy storage, aerospace equipment and other fields have raised demands for high-energy-density capacitors. Therefore, capacitors need to have a compact structure and a large number of winding layers. However, high interlayer pressure may lead to a decrease in the breakdown performance of BOPP. It is necessary to study the breakdown characteristics of BOPP films under pressure. The existing reference standards for micron-scale films mainly stipulate the electrode system, such as the form and material of the electrodes, while the application methods of pressure are rarely mentioned. Based on the references of “GB/T 13542.2-2009, Films for electrical insulation-Part 2: Test methods” and “GB/T 13542.2-2021, Films for electrical insulation-Part 2: Test methods”, this paper adds an adjustable pressure module and studies the influence of the application rate and application time of pressure on the breakdown characteristic test. The results show that when the application rate of pressure increases from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.078 \text{MPa} / \mathrm{s}$</tex> to approximately <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.111 \text{MPa} / \mathrm{s}$</tex>, the breakdown field strength value decreases by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{3. 8 2 \%}$</tex>, and the dispersion decreases from about 8.61 to 6.41. Considering the reliability of the data in the breakdown experiment and the fact that the pressure increase rate during the manufacturing and winding of actual capacitors is not fast, the pressure rate should be minimized as much as possible in the experiment. The application time of pressure within <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{0}-\mathbf{2 4}$</tex> hours has no significant influence on the breakdown field strength value and dispersion, and its influence can be ignored. The research results of this paper can provide a reference for the breakdown test method of micronscale films under pressure.