"Common faults of electrolytic capacitors include capacity reduction, capacity disappearance, breakdown short circuit and leakage. The capacity change is caused by the gradual drying up of the electrolyte inside the electrolytic capacitor during use or placement, while the breakdown and leakage are generally caused by the high applied voltage or poor quality. The resistance gear of the multimeter is generally used to judge the quality of the power capacitor."
1. Filtering function: in the power supply circuit, the rectifier circuit changes AC into pulsating DC, and a large capacity electrolytic capacitor is connected behind the rectifier circuit to make use of its charge and discharge characteristics (energy storage function) to change the pulsating DC voltage after rectification into a relatively stable DC voltage. In practice, in order to prevent the power supply voltage of each part of the circuit from changing due to the load change, the output end of the power supply and the input end of the load are generally connected with dozens to hundreds of micro methods of electrolytic capacitors. Since large capacity electrolytic capacitors generally have certain inductance and can not effectively filter high-frequency and pulse interference signals, a 0.001-0 LPF capacitance to filter out high-frequency and pulse interference.
2. Coupling: in the process of low-frequency signal transmission and amplification, capacitor coupling is often used to prevent the interaction between the static working points of the front and rear circuits. In order to prevent excessive loss of low-frequency components in the signal, electrolytic capacitors with large capacity are generally used.
Next, we need to know how to judge electrolytic capacitors
Common faults of electrolytic capacitors include capacity reduction, capacity disappearance, breakdown short circuit and leakage. The capacity change is caused by the gradual drying up of the electrolyte inside the electrolytic capacitor during use or placement, while the breakdown and leakage are generally caused by the high applied voltage or poor quality. Generally, the resistance gear of the multimeter is used to measure the power capacitance. The specific method is: short circuit the two pins of the capacitor for discharge, and connect the black probe of the multimeter to the positive pole of the electrolytic capacitor. The red probe is connected to the negative pole (for a pointer multimeter, the probes are mutually adjustable when measured with a digital multimeter). In normal conditions, the probe should first swing in the direction of low resistance, and then gradually return to infinity. The greater the swing amplitude of the meter needle or the slower the return speed is, the greater the capacity of the capacitor is. On the contrary, the smaller the capacity of the capacitor is. If the meter needle does not change anywhere in the middle, it indicates that the capacitor is leaking electricity. If the resistance indication value is very small or zero, it indicates that the capacitor has broken through the short circuit. Because the battery voltage used by the multimeter is generally very low, it is more accurate to measure the capacitance with low withstand voltage. When the withstand voltage of the capacitor is high, Although the measurement is normal during driving, leakage or breakdown may occur when high voltage is applied.
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