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# Capacitor-general knowledge analysis

1. The meaning of a capacitor: a physical quantity that measures the capacity of a conductor to store charges.

2. Capacitor: C (capacitor)

3. Symbols for Capacitors in Circuits: C or CN (Volume Discharge)

4. Common units of capacitors: millimeter method (mF), micromethod (uF), nanometer method (nF), skin method (pF)

5. Unit conversion of 2.5 capacitors: 1 farad = 103 millimeter method = 106 millimeter method = 109 nanometer method = 1012 skin method; 1 pf = 10-3 NF = 10-6 UF = 10-9 MF = 10-12 f;

6. Functions of Capacitors: DC Isolation, Bypass, Coupling, Filtering, Compensation, Charging and Discharging, Energy Storage, etc.

7. Characteristic of Capacitor: Capacitor capacity is the capacity to store electric energy. Capacitance’s impediment to AC signal is called capacitance reactance, which is related to the frequency and capacity of AC signal. The main characteristics of capacitors are DC-AC, low frequency resistance and high frequency.

8. capacitors are usually represented by “C” plus numbers in circuits. For example, C25 represents capacitors numbered 25.

9. The method of capacitor identification is basically the same as that of resistance identification, which is divided into three kinds: direct marking method, color marking method and number marking method.

• A. The direct labeling method is to express the nominal value of capacitance in terms of numbers and units in the capacitor itself. For example, 220MF means 220UF; 01UF means 0.01UF; R56UF means 0.56UF; 6n8 means 6800PF.
• B. The numeric representation of non-standard units. One to four digits are used to represent the valid digits, generally PF, while the capacity of electrolytic capacitors is UF. For example, 3 represents 3PF; 2200 represents 2200PF; 0.056 represents 0.056UF;
• C. Number representation: Generally, three digits are used to represent the size of capacity, the first two are valid digits, and the third is 10 times the power. For example, 102 is 10102=1000PF; 224 is 22104=0.2UF.
• D. The main parameters of capacitors are represented by color rings or color dots. The colour mark method of capacitors is the same as that of resistors. Capacitor deviation symbol: +100%-0-H, +100%-10%-R, +50%-10%-T, +30%-10%-Q, +50%-20%-S, +80%-20%-Z.

10. Capacitance Classification: According to polarity, it can be divided into polar capacitance and non-polar capacitance. The common electrolytic capacitance is polar, with positive and negative poles.

11. The main performance indicators of capacitors are: capacitance of capacitors (i.e. capacity to store charges), withstand voltage (i.e. the maximum DC voltage or the effective value of the maximum AC voltage that capacitors can work reliably for a long time in the rated temperature range), withstand temperature (i.e. the maximum operating temperature that capacitors can withstand). .

12. Capacitor brands are: main board capacitors are divided into two types: platform and Japanese, Japanese brands are: NICHICON, RUBICON, RUBYCON (ruby), KZG, SANYO (Sanyo), PANASONIC (Panasonic), NIPPON, FUJITSU (Fujitsu) and so on; Taiwan brands are TAICON, G-LUXCON, TEAPO, CAPXON, OST, GSC, RLS, etc.

13. Formulas for calculating series and parallel capacitors: C series: 1/C=1/C1+1/C2+1/C3+…. +1/CN C parallel C=C1+C2+C3++CN~6

14. Measurement of Capacitors:

• A. When disconnecting from the line, the multimeter R *1k block is used. Before the detection, the two pins of the electrolytic capacitor are touched to release the residual charge in the capacitor. When the pen is connected, the meter needle deflects an angle to the right, then the meter needle turns slowly to the left, and finally the meter needle stops. The resistance indicated by the stop of the meter needle is the leakage resistance of the capacitor. The greater the resistance, the better, it should be close to infinity. If the leakage resistance is only several tens of kiloohms, the leakage of this electrolytic capacitor is serious. The larger the angle of the needle swinging to the right (the needle should swing to the left), the larger the capacity of the electrolytic capacitor, and vice versa, the smaller the capacity.
• B. On-line direct detection is mainly to detect whether the capacitor has been opened or broken down. However, the leakage fault is generally not accurate because of the influence of external circuit. When the circuit is disconnected, the charge remaining in the capacitor is discharged first with the multimeter R * 1 block. If the needle is deflected to the right during measurement, the internal circuit break of the electrolytic capacitor is explained. If the resistance value indicated after the needle deflects to the right is very small (close to short circuit), it indicates that the capacitor is seriously leakage or has been broken down. If the needle does not turn to the right, but the resistance value indicated is not very small, it indicates that the open circuit of the capacitor may be very large, and it should be further detected after disconnecting the circuit.
• C. When the line is on-line, if it is suspected that the breakdown fault of the electrolytic capacitor exists only in the on-line state, the circuit can be energized, and then the DC voltage at both ends of the capacitor can be measured with a multimeter DC block. If the voltage is very low or 0 V, the capacitor has been broken down. If the sign of positive and negative electrodes of electrolytic capacitors is not clear, the positive and negative electrodes of electrolytic capacitors must be distinguished first. Measure two times with a multi-meter pen, with a large leakage (small resistance value) as the criterion. One foot of the black pen is negative, and the other foot is positive.