The metallized layers in these capacitors are <100 nm thick. The two films are wound around a hollow mandrel. On each end of the winding is a sprayed-on metal schoopage. The schoopage connects the metallizations of the film to the terminals of the package. Each film has one clear edge.
Metallized film capacitors generally use polypropylene as the dielectric film, and use the metallized layer evaporated on the dielectric film as the electrode, which are the important power devices.
When the metallized film capacitor is working at a high field strength, the weak point of the dielectric film is first broken down, and the energy stored in the dielectric film at the breakdown point is released instantaneously, causing the breakdown point and the surrounding metal electrodes to evaporate and form insulation recovery.
After successful self-healing, the metallized film capacitor can continue to work, so this type of capacitor has high reliability (Sarjeant et al., 1998). Although metallized capacitors rarely fail, once a metallized film capacitor has an accident, the impact on the application system cannot be ignored.
However, the thick metal foils prevent these capacitors from exhibiting the self-healing phenomena observed in metallized film capacitors . Metallized film capacitors are non-polar. They consist of two polymer films on which thin coatings of metal have been deposited. The films are wound and packaged into a capacitor as shown in Fig. 1.
Metallized film capacitors are used to reduce electromagnetic interference (EMI) in electric power mains due to their high voltage capability and their open circuit failure mode, which aids in safe operation. This paper presents a comprehensive review of metallized film capacitors used for EMI filtering and their failure modes and mechanisms.