​What is the method of electrolytic capacitor withstand voltage test circuit? The withstand voltage of a capacitor indicates the voltage that the capacitor can withstand when it is used continuously under certain conditions. If the working voltage applied to the capacitor exceeds the rated voltage, the insulating medium inside the capacitor may be broken down, resulting in short circuit between electrodes or serious leakage. Therefore, the working voltage of the capacitor should not be greater than its rated withstand voltage to ensure the reliable operation of the circuit. For electrolytic capacitors, leakage current is an important performance index.

The leakage current of electrolytic capacitor is closely related to the voltage, and the leakage current increases with the increase of working voltage. When the working voltage is close to the anode enabling voltage, the leakage current will rise sharply. By testing the leakage current of electrolytic capacitor, the limit withstand voltage and rated withstand voltage can be calculated. It has direct reference significance for the value of capacitor withstand voltage in the circuit.

According to this principle, a capacitor withstand voltage tester is designed and manufactured. The circuit is simple, the cost is low, and the manufacture is easy.

The type of transformer T1 and T2 are the same, back-to-back docking, providing two groups of high and low voltage power supply, and playing the role of isolation. After rectifying and filtering, R1, DWL, Q1, ral-ral1 are used to form a constant current source with adjustable current. After rectifying and filtering, the high voltage is divided by RBL ~ rblo, dw2, and output adjustable DC voltage by Q2. When using, select the appropriate voltage UC and current JC, and connect the measured capacitance to two points of CXA and CXB. At this time, you will see the pointer of the voltmeter slowly deflect and come to rest after reaching a certain position. The voltage indicated by the pointer is the withstand voltage of the capacitor when the leakage current is LC.

Band switches K3 and K4 (11 positions in each single gear) are test voltage and current (i.e. leakage current) selection switches with their test ranges.

1. Adjust the test voltage to a gear higher than the rated voltage of the capacitor. For example, test the application capacity of 35V. The higher the gear is, the higher the power consumption of transistor Q1 will be.

2. Select the appropriate test current. The test current should be selected according to the capacitance. The larger the capacitance is, the larger the test current is. For 4700 μ If the capacitance is larger than 10 Ma, the test current can be selected; For 1000-4700 μ F, capacitance, about 5mA test current can be selected: for 10 μ 0.2 ~ 1mA test current can be selected for capacitance below F.

3. The red crocodile is clamped to the positive pole of the capacitor, and the Black Crocodile is clamped to the negative pole of the capacitor. After connecting, we can see that the pointer of the voltmeter first deflects slowly at a constant speed. Under normal conditions, the deflection position should exceed the rated voltage. When it reaches a certain value, the pointer deflection becomes slower and slower, and finally comes to a standstill. At this time, the leakage current of the capacitor is equal to the constant current of Q1 collector, and the voltage indicated by the voltmeter. Therefore, the withstand voltage of the capacitor when the leakage current is IC can be roughly considered as the limit withstand voltage of the capacitor.

4. After the test, close the switch K2 and remove it after the capacitor is discharged.