The cause of damage to the film capacitor

A film capacitor is a capacitor in which a metal foil is used as an electrode, and a plastic film such as polyethylene, polypropylene, or polycarbonate is stacked from both ends and wound into a cylindrical shape, and is widely used. There are also imaginary reflections that are reflected in damage, including self-healing damage and non-self-healing damage.

Film capacitors Due to raw materials and manufacturing processes, early damage is mostly due to manufacturing reasons. Because of the possibility of impurities in the medium during the manufacturing process, mechanical damage, pinholes, low cleanliness, etc., problems such as overvoltage, overcurrent and surrounding high and low temperatures may cause problems such as thin film capacitors. breakdown. Sparks are usually generated during breakdown, further expanding the range to form a multilayer short circuit or even a short circuit of the entire component.

The voltage across the component in series with the breakdown element will increase, causing the voltage across the remaining groups to increase and the current through each component to increase. This series of reactions will lead to rapid aging of individual components and increase heat generation. At the same time, partial discharge of the edge of the plate will also occur under the action of a higher voltage. After a certain period of time, the film capacitance of the entire group in series with the faulty component will be successively broken down, and a new group will be connected. The number of groups is further reduced, the component voltage is further increased, the overcurrent phenomenon is more serious, the medium is further deteriorated, the temperature is further increased, and the arc is further increased. As this continues, the component damage is more and more, and the casing expansion becomes more and more serious.

The thickness of the film capacitor also affects the self-healing properties of the capacitor. The thinner the metal film, the stronger its self-healing properties, but the more fragile it is with the gold-plated layer. If the film capacitor is required to have good self-healing properties and sufficient thickness to increase the gold-injection strength, then an edge-thickened film capacitor can be used, which has a thickened metallized film wound core. It can withstand the impact of surge current, high reliability, good self-healing performance and long service life. Its theoretical life can reach 100 years.