Film capacitance absorption coefficient

Film capacitors are ubiquitous in our lives. Its applications are very wide. For example, our common air conditioners, refrigerators, washing machines, water heaters, etc. Today, the editors will take a look at the film capacitors and what is the absorption coefficient of the film capacitors. The effect of the absorption coefficient of the film capacitance and the occurrence of an abnormality. Let's take a look at the progress of the editor together.

The film capacitor is a capacitor in which a metal foil is used as an electrode and a plastic film such as polyethylene, polypropylene, polystyrene 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 have little change 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 charging and discharging of the capacitor. In the absolute 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. Of course, this is an ideal state, in fact, the current technology can not be achieved.

If the absorption coefficient is too large, the charging/discharging response of the capacitor is severely delayed, the time constant of the ultra-low frequency smoothing filter becomes large, the zero point of the DC amplifier is disturbed, the unidirectional drift, the ripple of the power supply circuit is increased, and the like, so that the film capacitor is The smaller the absorption coefficient, the better.