The air conditioner compressor does not start, it may be its problem-capacitor

The air conditioner compressor does not start, it may be its problem-capacitor

The main functions of capacitors (capacitors for short) in the electronic circuit of air conditioners are filtering, delay, boosting, energy storage, bypass, decoupling, etc., and can also be used to start the compressor. The symbol of the capacitor is shown in the figure below. The two most important parameters of a capacitor are withstand voltage and capacitance.

Capacitor identification symbol

　　①Basic capacitance symbol, such as ceramic capacitor, electrolytic capacitor, mica capacitor, film capacitor.

　　②-⑥There are polar capacitors, electrolytic capacitor symbols, the bent piece is the negative pole, and the hollow is the positive pole.

　　⑦ Adjustable capacitance symbol.

　　⑧ Fine-tune the capacitor symbol.

　　1. Classification and labeling method of capacitors

Capacitors can be divided into ordinary capacitors and electrolytic capacitors according to their structure, and can be divided into fixed capacitors and variable capacitors according to their uses. Ordinary capacitors (such as magnetic chip capacitors) have no polarity and there is no problem of wrong connection.

　　Electrolytic capacitors have polarities, so they cannot be connected wrongly in the circuit: if they are connected wrongly, the electrolytic capacitor will break down. The electrolytic capacitor has a long positive pin and a short negative pin. The case is marked with positive and negative polarity, so it is easy to distinguish.

　　 Domestic capacitors are marked with capacity and withstand voltage: foreign CK-type ceramic capacitors are expressed in numbers, that is, a 3-digit number is used to indicate the capacity value, followed by an English letter to indicate the error. Among them, the first two digits represent the effective digits 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 indicated capacity unit is pF, and English letters represent errors. The letter of capacitance error indicates the code table as shown in the following table.

2. Capacitance detection

　　 (1) Checking the quality of the capacitor The common faults of the capacitor are open circuit, short circuit and leakage. The fault can be easily detected with a multimeter, but if the capacitance is small or there is a slight leakage, it is more difficult to directly measure with a multimeter. Except for electrolytic capacitors, the resistance of general capacitors is very large, above tens of megohms. If it is less than a few megohms, it means the capacitor is leaking.

　　 Large-capacity electrolytic capacitors can be measured with a multimeter for high-barrier measurement, that is, remove the two terminals connecting the capacitor, and use a wire to directly connect the two terminals of the capacitor to discharge. After the capacitor is discharged, if the pointer jumps when touching the two legs of the capacitor with a multimeter pen, and then slowly returns to the direction of infinite resistance, it means that the capacitor is normal; if the pointer jumps in a small range, it indicates that the capacitance is small; if the pointer returns after it jumps Stopping somewhere on the resistance value means that the capacitor is leaking. For small-capacity capacitors, you can replace them with capacitors of the same type to judge whether they are good or bad.

capacitance 　　 (2) Electrolytic capacitor polarity discrimination The electrolytic capacitor is charged in the forward direction, and the leakage current is small: reverse charging, the leakage current is large. According to this feature, capacitors with unknown polarity can be judged. Use a multimeter with R×10 and R×100 gears, the two test pens respectively touch the two poles of the capacitor, and the pointer swings to the right and gradually returns to some place to the left. Note the scale pointed by the pointer, and then adjust the test pen again and measure it twice. The data is compared, the first black test lead with a small resistance is connected to the positive electrode of the capacitor.