Study on failure of DC-link capacitor destruction test

In recent years, domestic capacitor manufacturers have developed DC-link capacitors under the guidance of the State Grid Corporation of China (SGCC), and have conducted performance optimization iterations of a large number of domestically produced DC-link capacitors. This paper presents a failure analysis of a 2.8kV-10mF DC-link capacitor sent by a manufacturer, which failed during destruction test according to the SGCC's test program. The failure of the capacitor is introduced, and the cause of the failure is analyzed based on the test results. Then, an anatomical analysis is conducted on the faulty specimen, and it is finally determined that the reason for the failure is that, with the design of the outer wrapping of the 5mm polypropylene film, the heat dissipation conditions of the capacitor components deteriorate, and the internal temperature is too high in the rated ripple current, resulting in damage to the insulation between the ends of the capacitor and increased leakage current. At the same time, the high temperature caused by the heat of the components causes poor contact between part of the component ends and the converging copper row of the connection, and the poor contact generates a continuous discharge current. The heat generated by the discharge erodes the capacitor component ends and the converging copper row, causing further damage to the insulation properties between the capacitor core and the shell.