Commonly used capacitors

　　Commonly used capacitors

　　1. Ceramic Capacitors

　　Ceramic capacitors have strong insulation performance, high insulation resistance, can be used in high-voltage circuits, and have good heat resistance characteristics; ceramic materials have a wide range of temperature coefficients, and capacitors with different temperature coefficients can be produced to suit different applications. The loss tangent of ceramic capacitors has a very small relationship with frequency, and can be widely used in high-frequency circuits of switching power supplies. The capacitance of ceramic capacitors is relatively small, generally only a few picofarads to a few tenths of a microfarad. Ceramic capacitors are generally wafer-shaped, cylindrical or laminated. Low mechanical strength and easy breakage are the disadvantages of ceramic capacitors.

　　2. Film capacitors

　　Film capacitors are made of materials such as polystyrene, polytetrafluoroethylene, polypropylene or polycarbonate. Film capacitors are divided into polar organic film and non-polar organic film capacitors. Polar organic film capacitors have the advantages of large capacitance to volume ratio, high temperature resistance, and high voltage strength. Non-polar organic film capacitors have the advantages of small loss tangent, large insulation resistance, small dielectric absorption coefficient, and negative temperature coefficient. If a metal film is uniformly plated on one side of an organic film and then rolled to form a capacitor, it is called a metalized organic film capacitor. Film capacitors have cylindrical, flat, laminated block shapes and so on. In the product model of film capacitor, C means capacitor, and B means polystyrene. It is small in size, light in weight, and has a "self-healing" function.

　　Film capacitors include six types of film capacitors including polystyrene capacitors, polytetrafluoroethylene capacitors, polypropylene capacitors, polyester capacitors, and polycarbonate capacitors. Polystyrene film capacitors have the following characteristics:

　　a) Wide withstand voltage range, 30V~15KV. The working voltage of ordinary polystyrene capacitors is 100V, and the working voltage of high-voltage polystyrene capacitors can reach 10KV~15KV;

　　b) The insulation resistance is high, generally greater than or equal to 100000000000 ohms, so the leakage current is small. It can still maintain 95% of the charge after being charged for 1000 hours, while the low-quality capacitors are charged for 200 hours after being charged. Just put it all out

　　c) The tangent value of the loss angle is large, and metallized polystyrene capacitors should not be used in high-frequency circuits;

　　d) Capacitors have a wide capacity range, and can produce 100PF~100uF capacitors;

　　e) The accuracy of the capacitor is high, and it can produce 0.3%~0.1% high-precision capacitors;

　　f) The temperature coefficient is small, the performance is stable, acid and alkali resistance, moisture resistance, etc., pay attention to the marked withstand voltage and capacitance when using it.

　　3. Electrolytic capacitor

　　Electrolytic capacitors have adopted many new technologies in the production process. Expand the etching rate of electrode foil, improve the chemical stability and thermal stability of the electrolyte film, develop high-conductivity electrolyte with good heat resistance, and use high-airtight heat-resistant sealing linings, etc. At present, the factors that affect the basic performance of aluminum electrolytic capacitors, such as the operating temperature, high-frequency impedance, and service life, are electrolytes. The sealing gasket of the capacitor plays an important role in controlling the drying of the electrolyte, so the gasket material has a great influence on the life of the aluminum electrolytic capacitor. The following parameters should be considered when choosing aluminum electrolytic capacitors: rated capacity, nominal temperature (generally 105°C), withstand voltage and leakage current. All aluminum electrolytic capacitors that can withstand various tests are rarely damaged in practical applications.

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