How to screen electrolytic capacitors?

Electrolytic capacitors are a kind of components in the electronics industry that are difficult to control. There are many product quality problems caused by electrolytic capacitors. Many manufacturers do not know how to check the quality of electrolytic capacitors and have to buy brand-name electrolytic capacitors at high prices, which will increase A lot of cost.






1. Principle: The main problem of electrolytic capacitors used in electronic ballasts is that the withstand voltage is insufficient or the temperature coefficient is poor during operation, which causes damage to the electrolytic capacitors. This method is to test the quality of the electrolytic capacitor through charging and discharging under the condition of the extreme working voltage of the electrolytic capacitor. If possible, it is better to screen at high temperature. If the performance of the electrolytic capacitor is not enough, when there is a slight leakage, the charge stored in other electrolytic capacitors will be discharged through the capacitor, and the capacitor with poor performance will be blown up as a result. The electrolytic capacitor with good performance is intact.


2. Selection of main components: T1 uses a 0-250V/1KW self-coupling voltage regulator, T2 needs to be customized, and the parameter is 500W, 220/380V step-up isolation transformer. The DC voltmeter uses 1000V range. S1 and S2 use linked switches, and it is best to use the emergency brake switch on the machine tool instead. An ordinary incandescent lamp can be used for the bulb. The fuse uses the delay fuse on the color TV.


3. Production method: first make a fixture, which can fix the pins of many electrolytic capacitors to be tested, and can be electrically connected reliably. Use another box to install everything in the box. Install the voltmeter, light bulb, switch and voltage regulating handle on the outer surface of the box. After connecting the electrical wiring, you can screen the electrolytic capacitors.


4. Instrument debugging method: first adjust the working voltage according to the requirements of the electrolytic capacitor, mount the electrolytic capacitor on the clamp, close the box cover, and press the power switch. At this time, the bulb lights up and the pointer of the voltmeter is rising. , Which means that the circuit is charging the electrolytic capacitor, and when the voltage reaches the specified voltage, the bulb is extinguished. Turn the switch again to make the switch jump. At this time, the light bulb lights up, indicating that the electrolytic capacitor is discharging and the voltmeter pointer is dropping. This indicates that the instrument is working properly.


5. How to select the rated working voltage: In general, the rated working voltage is selected as 110-120% of the electrolytic capacitor identification voltage. If the identification voltage is 400V, then the working voltage is selected between 440-480V. If the instrument is at high temperature, select 440V, and at low temperature, select 480V. Screening operation method: first adjust the working voltage according to the electrolytic capacitor identification, turn off the power switch, install the electrolytic capacitor, clamp, and cover the box. Turn on the power switch, turn it off, repeat three times, then turn on the power switch, keep it for half an hour, repeat the switch three times, and finally turn off the power switch and take out the electrolytic capacitors. This step of screening is completed. Note: If the electrolytic capacitors that explode, rupture, or leak during the test are all unqualified products, others can be used as qualified products. A comprehensive screening method also includes the detection of capacitance, leakage current and loss angle.