Absorption coefficient and life level of film capacitor

1. The absorption coefficient of the film capacitor

The 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. The film capacitance of polypropylene has a small absorption coefficient, and the capacity and loss tangent tg σ vary little with temperature, and the dielectric strength increases with temperature. This is a feature of his, which is difficult for other capacitors to possess. . So what is its absorption coefficient? This is a numerical value used to describe the dielectric absorption phenomenon of a film capacitor. We call it the absorption coefficient, which is related to the dielectric, the polarization of the dielectric, and the absorption phenomenon of the capacitor. This coefficient is not the same. Different manufacturers and different model batches will be different. Even each film capacitor produced by the same manufacturer model batch may have different.

The dielectric absorption effect of the film capacitor determines the low frequency characteristics of the capacitor. The smaller the absorption coefficient, the better the film capacitor and the faster the charge and discharge of the capacitor. In the *ideal state, if the absorption coefficient can be 0, the dielectric (ie, the insulator) has no polarization under the action of the applied electric field, the dielectric surface has no traction binding force on the charge, and the capacitor charge and discharge response has no hysteresis.

2. Lifetime rating of film capacitor

Film capacitors are widely used in electronics, home appliances, telecommunications, electric power, electrified railways, hybrid electric vehicles, wind power generation, solar power generation and other industries. Due to non-polarity, high insulation resistance, excellent frequency characteristics, and low dielectric loss. Other advantages are favored by major manufacturers. According to the CQC standard, the level of the capacitor is divided into four levels of ABCD, the level A is continuous operation of 30,000 hours, the B level is 10,000 hours, the C level is 3000 hours, and the D level is 1000 hours.

The life of a thin film capacitor is affected by temperature and shortens with increasing temperature. For example, a quality C-level capacitor, his life is 3000 hours, it can work normally for 3,000 hours, even longer, under normal temperature (room temperature) work. But if its working temperature is at his extreme working temperature, its normal working time may be only 500 hours. And if the temperature exceeds its limit operating temperature, then it will not work properly and will be damaged. Therefore, in order to extend the life of the film capacitor, it is necessary to operate it at a suitable temperature.