The capacitor is a complicated thing because it is composed of many basic components. Due to the raw materials and manufacturing process, the capacitor medium produced by many small factories is prone to impurities, mechanical damage, pinholes, and low cleanliness.
The early damage of the capacitor is mostly due to manufacturing reasons. High voltage capacitor: usually composed of multiple components in parallel, each component is made of aluminum foil as an electrode, and a solid medium is placed between the electrodes. It is made by winding. The plate area of the component is very large. Due to raw materials and manufacturing processes, there may be impurities in the medium, mechanical damage, pinholes, and low cleanliness. This has become a hidden danger inherent in capacitors. In the system, due to overvoltage, overcurrent and surrounding high and low temperature caused by various reasons, these weak points will cause dielectric breakdown. During breakdown, sparks are usually generated to further expand the range, thereby forming a multilayer short circuit or even a short circuit of the entire component. The voltage on the element in series with the breakdown element will increase accordingly, and the element group in parallel with it will be shorted, so that the voltage on the remaining series group will increase, and the current through each element will also increase Increase. It will cause the rapid aging of various components and increase the heat generation. At the same time, a partial discharge at the edge of the plate will also be generated under the action of higher voltage. In addition, the discharge of the breakdown point will cause the impregnating agent to emit a large amount of gas. After a certain period of time, the other elements of the entire series group connected in series with the faulty component will break down in succession, and a new series group will be shorted. If it 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, the arc will be further increased, and the impregnating agent will further release the gas. getting more serious. In this case, the protection fuse and relay protection should promptly remove the faulty capacitor. If it cannot be removed, further breakdown will form a strong arc in the cabinet. Other parallel capacitors and system energy surges will be very short. Within a short period of time, the dielectric of the capacitor quickly ages and expands, and eventually the case expands. In severe cases, it will explode. This accident cannot be eliminated for the user. It belongs to the early damage of the capacitor, and the cycle is usually about one year. Only manufacturers try to improve product quality and strengthen detection methods in order to reduce the early damage rate. Therefore, when selecting the compensation capacitor, the conditional unit should try to choose a collective and self-healing capacitor with reliable performance.
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