Method of testing capacitors

1. Multimeter testing method

For fixed capacitors above 0.01μF. The R×1k block of a multimeter can be used to directly test whether the capacitor has the charging process and whether there is internal short circuit or leakage, and the capacity of the capacitor can be estimated according to the magnitude of the pointer swing to the right. During the test operation, first touch the two pins of the capacitor at will with two test leads, then change the test leads and touch again. If the capacitor is good, the pointer of the multimeter will swing to the right and then quickly return to the infinity position to the left. The larger the electric capacity, the larger the pointer swing. If the meter pen is repeatedly exchanged and touched on the two pins of the capacitor, the pointer of the multimeter never swings to the right, indicating that the capacity of the capacitor has been lower than 0.01μF or has disappeared. During the measurement, if the pointer cannot return to the infinity position to the left after swinging to the right, it indicates that the capacitor has leaked or has been broken down.

2. Simple fuse detection method

Use a fuse (the rated current In of the fuse is determined by the following formula: IN=0.8/C (A), where C is the capacitance of the capacitor) and the capacitor to be tested are connected in series to the 220V AC power supply. If the fuse is The fuse blows, indicating that the capacitor has been short-circuited. If the fuse of the fuse does not explode, after a few seconds of charging, cut off the power supply, and use a screwdriver with an insulating handle to short-circuit the two poles of the capacitor to discharge. Sparks occur, indicating that the capacitor is good. On the contrary, it means that the capacitance of the capacitor has become smaller or has been opened. Use this method to judge the quality of the capacitor should be repeated several times to get the correct conclusion.

3. Incandescent bulb and capacitor series detection method

Connect the incandescent bulb and capacitor in series to the 220V AC power supply. If the brightness of the incandescent bulb is darker than connecting it directly to the 220V AC power supply, the capacitor is good; if the incandescent bulb is not bright, it indicates the inside of the capacitor to be tested It has been disconnected; if the brightness of the incandescent bulb is the same as that when it is directly connected to the 220V AC power supply, it means that the capacitor has a short circuit.

4. Megger detection method

Megger (250V class) can also be used for testing. Shake the handle, if the pointer is at infinity, it means that the capacitor is open; if the pointer is at zero, it means that the capacitor is short-circuited. The ground test of the capacitor can also be done by connecting the terminals of the megohmmeter to the terminals and the shell of the capacitor respectively. Shake the handle, if the pointer is at zero, it means that the capacitor is connected to ground.

5. Measurement of capacitor capacitance

In the absence of special meters, a multimeter can be used to measure the capacitance of a power capacitor. The specific method is: use a fuse (its specification is determined by the capacitance of the capacitor) and the capacitor to be tested are connected in series to the 220V AC power supply. Use the AC voltage file of the multimeter to measure the voltage U (V) across the capacitor.

Use the AC current file of the multimeter to measure the current I (mA) through the capacitor. Because I=U/XC and XC=1/(2πfC), where f is the frequency of alternating current. So the capacitance of the capacitor CC=3.18&TImes; (I/U) (microfarad).