Capacitance is the electronic component that holds releases electric charge. The basic working principle of capacitor is charging discharging, of course, rectification, oscillation other functions. In addition, the structure of the capacitor is very simple, mainly composed of two positive negative electrodes the insulating medium sandwiched in the middle, so the type of capacitor is mainly determined by the electrode the insulating medium. In the circuit of main board, card power supply of computer system, several kinds of capacitors, such as electrolytic capacitor, paper capacitor porcelain capacitor, are applied, electrolytic capacitor is the main one.

The paper capacitor is composed of two layers of positive negative tin foil electrodes one layer of insulating wax paper sandwiched in the middle of the tin foil, which is disassembled stacked into a flat rectangle. The rated voltage is generally between 63v 250V, the capacity is small, which is basically the order of PF (leather method). Due to the use of rigid plastic shell resin sealed packaging, modern paper capacitors are easy to age, because they basically work in the low-voltage area, the withstand voltage value is relatively high, so the possibility of damage is small. In case of electric damage, the general symptom is a heating on the surface of the capacitor.

1. Capacitor is mainly used in AC circuit pulse circuit. In DC circuit, capacitor generally plays the role of isolating DC.

2. The capacitor is an energy storage element, which neither generates nor consumes energy.

3. Capacitor is an important device to improve the power factor in the power system; in the electronic circuit, it is the main component to obtain the functions of oscillation, filtering, phase shift, bypass, coupling, etc.

4. Because the load used in the industry is mainly the inductive load of the motor, it is necessary to combine the capacitive load of capacitance to make the grid balanced.