The basic unit of capacitance, conversion method and common capacitance classification



The basic unit and conversion method of capacitance

The basic units of capacitance are: farad F, millifarad mF, microfarad μF, nanofarad nF, picofarad pF

Conversion method: 1F=1000mF 1mF=1000μF 1μF=1000nF1nF=1000pF

Conversion: 1F=103mF=106μF=109nF=1012pF

Commonly used various capacitor classification (by material) usage and picture display:

1. Porcelain chip capacitors are cheap and have small capacity. They are mainly used in low-frequency circuits and can be seen everywhere on various circuit boards.

2. Polyester capacitors have the same characteristics and uses as above, and are generally green.

3. Monolithic capacitors are very expensive, have small capacity and stable properties, and are generally light yellow.

4. Electrolytic capacitors have large capacity and have positive and negative poles. It is mainly used in power circuits. When used for filtering, attention should be paid to whether the withstand voltage value meets the circuit requirements.

5. Mica capacitors, withstand voltage (250v-450v), small capacity, very expensive, and large in size. It is used in the important part of the communication machine.

6. Tantalum capacitors are mostly used in power amplifier circuits. They have long life, high temperature resistance, high precision, and excellent high-frequency filtering performance, but they have low capacity and relatively expensive prices.

7. CBB film capacitors, also called polypropylene capacitors, are generally brown, and are commonly used in resistance-capacitance step-down circuits.

8. The starting capacitor is relatively large in size. A large and suitable starting capacitor is connected in series with the starting winding of the motor, so that a 90-degree phase is formed between the starting winding and the running winding of the motor to make the motor rotate.

9. Audio coupling capacitors, pre-amplifiers, and crossovers are often used, and some are very expensive.

10. Resonant capacitor, such as the 0.3 microfarad resonant capacitor commonly found on the mainboard of an induction cooker.

11. Safety X capacitors are generally yellow, and can be divided into three types according to the withstand voltage value: X1, X2, and X3, and X1 has the highest withstand voltage. When installing, it is generally connected between the neutral line and the live line. The nameplate is usually marked with safety certification mark, withstand voltage value, capacity and other words. Unlike ordinary capacitors, even after the external power supply is disconnected, the charge inside the capacitor will remain for a long time, but safety capacitors will not.

12. Safety Y capacitors, generally blue, flat and round like piezoresistors, are generally installed between the cold ground and the hot ground or between the live wire and the ground at the input end, between the neutral wire and the ground, or is between the output terminal and ground. It has the function of suppressing common mode interference.

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