The main functions of capacitors (referred to as capacitors) in the electronic circuit of the air conditioner are filtering, delay, boost, energy storage, bypass, decoupling, etc., and can also be used to start the compressor. The symbol of the capacitor is shown below. The two most important parameters of the capacitor are the withstand voltage and the capacitance.
Capacitance identification symbol
1 basic capacitance symbol, such as ceramic capacitor electrolytic capacitor mica capacitor film capacitor.
2-6 has a polar capacitor, electrolytic capacitor symbol, the bent piece is the negative pole, and the hollow is the positive pole.
7 adjustable capacitor symbol.
8 trimmer capacitor symbol.
1. Classification and Labeling Method of Capacitor Capacitor can be divided into ordinary capacitor and electrolytic capacitor according to its structure. It can be divided into fixed capacitor and variable capacitor according to the application. Ordinary capacitors (such as disk capacitors) are non-polar and there is no problem with the connection.
The electrolytic capacitor has polarity and cannot be connected incorrectly in the circuit: if it is connected incorrectly, it will cause breakdown of the electrolytic capacitor. The electrolytic capacitor has a long positive lead and a short negative lead. It is marked with positive and negative polarity on the outer casing, so it is easy to distinguish.
Domestic capacitors are marked with capacity and withstand voltage: foreign CK-type ceramic capacitors are digitally represented, that is, a 3-digit number is used to represent the capacity value, followed by an English letter to indicate the error. Among them, the first two digits represent the effective number of the capacity, and the third digit represents the magnification. If the third digit is 9, it means that the magnification is 10 instead of 10°. The unit of capacity represented is pF, and the English letters represent the error. The letter representation of the capacitance error is shown in the table below.
For example, 220 means 22×10^0pF=22pF, 23 means 22×10^3pF=0.022uF, and 104 means 10×10^4pF=0.1uF with an error of ±10%.
2. Capacitance detection
(1) Capacitor with good or bad capacitance The common faults are open circuit, short circuit, and leakage. The fault can be easily checked with a multimeter, but if the capacitance is small or slight leakage, it is more difficult to measure directly with a multimeter. In addition to electrolytic capacitors, the general capacitance is very large, above tens of megaohms. If it is less than a few megaohms, it means that the capacitor is leaking.
The large-capacity electrolytic capacitor can be measured by a multi-block high-blocking, that is, the two ends of the connecting capacitor are removed, and the two terminals of the capacitor are directly connected to the discharge. After the capacitor is discharged, use the multimeter to touch the capacitor with two feet. If the pointer jumps, then slowly return to the resistance value infinite direction, indicating that the capacitor is normal; if the pointer jumps in a small range, it means that the capacitance is small; if the pointer jumps, it returns. Stopping at a certain resistance does not move, indicating that the capacitor is leaking. For small-capacity capacitors, replace them with the same type of capacitors to judge whether they are good or bad.
(2) The polarity of the electrolytic capacitor discriminates that the electrolytic capacitor is being charged in the forward direction, and the leakage current is small: reverse charging and large leakage current. According to this feature, the capacitance of unknown polarity can be judged. Use the multimeter R × 10 block, R × 100 block, the two test pens respectively contact the two poles of the capacitor, the pointer swings to the right and gradually returns to the left somewhere, do not move, write down the scale indicated by the pointer, and then measure the meter again, twice The data is compared, and the black pen with a small resistance is connected to the positive pole of the capacitor.
Post time: Mar-22-2019