Study on insulation failure characteristics of all-film pulsed capacitors

The all-film pulsed capacitor is an important energy storage unit for many high-power pulse devices, and its lifetime will seriously affect the stability and reliability of the device operation. In this paper, based on the working conditions of the linear transformer drive source, a test platform is designed and built, and the life test of the all-film pulsed capacitors used in the linear transformer drive source under DC and pulse conditions is carried out respectively, and it is found that the failure mode of the capacitor is mainly insulation breakdown, and the life of the capacitor is widely dispersed. The failure capacitors in the dismantling test were disassembled, and the breakdown points were found to be mainly concentrated in the folds, creases of the components, and winding arcs on both sides of the capacitor components, and the electric field simulation showed that the cause of the breakdown in the above areas was the electric field distortion. The microscopic observation of the films with different lifetime failure capacitors was carried out by SEM, and it was found that the presence of aluminum metal impurities on the early failure capacitor films was the main reason for their early failure. However, there are different degrees of damage marks on the surface of the capacitor film after a long life test, and the severity of the damage gradually deepens and shows dendritic with the increase of the capacitor charge and discharge times, indicating that the cause of the fatigue failure of the capacitor is related to the aging damage of the insulating medium. Based on the test results and analysis, an optimal design idea to improve the service life of the full-film pulse capacitor is proposed.