Qunio Electronics tells you how to increase the life of electrolytic capacitors
Article Source：QUNIO ELECTRONICS
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issuing time：2019-04-11
1、Control the ripple current value during operation
Aluminum electrolytic capacitors are used in pulsating circuits, causing power consumption. The main factor for heating and heating is the ripple current (the ripple voltage for smaller capacitors). The general relationship between failure rate and temperature is generally The ripple current is measured only under the DC voltage without ripple, and the internal center temperature of the core is almost the same as the ambient temperature. However, in practical applications, the heat generated by the ripple current can raise the temperature of the core center, and can reach several tens of degrees Celsius at the highest. (The temperature rise of the core depends on the ambient temperature of the electrolytic capacitor and the control of the ripple current). Therefore, the high ripple current tends to cause the electrolyte of the core to dry out, and the capacitor fails early. At the same time, the long-time ripple current exceeds the specified value, which is also one of the factors that cause the capacitor explosion-proof valve to open.
2、Select a capacitor with a small leakage current value
As an electrolytic capacitor for long-life use, in addition to the above four factors, it is also necessary to select a capacitor with a particularly small leakage current in the same type. This indicates that it has a higher quality oxide film and a suitable working electrolyte. Once the ambient temperature is high, the corresponding leakage current increases slowly. Otherwise, in the case of mutual influence, when the leakage current increases sharply, the internal temperature will rise, which in turn causes the leakage current to rise again, and deteriorates until the thermal balance is lost and destroyed.
3、Reduce the upper limit of the rated voltage
Lowering the upper limit of the rated voltage, that is, reducing the working field strength of the dielectric oxide film, will apply to electrolytic capacitors. After half the load reduction, the life of the capacitor can be increased by as much as two orders of magnitude.
In fact, if the aluminum oxide film is damaged and corroded, the repair oxide film can only be performed at the highest working voltage, and it is difficult to restore the thickness of the oxide film under the original formation voltage value, so the operating voltage is excessively lowered, and the aluminum electrolytic capacitor is excessively reduced. It is not the most appropriate measure.
4、Reduce the ambient temperature
Reducing the ambient temperature so that the electrolytic capacitor does not work at the upper temperature category, and also consider the thermal effects of the capacitor itself, which is especially important for liquid electrolyte type products. If high temperature is generated, the leakage current will increase sharply, the gas will increase, and the outer casing will be in a state of rapid increase in internal pressure; in addition, the high temperature can accelerate the drying of the electrolyte and shorten the life of the product. Therefore, for electrolytic capacitors with long life requirements, the operating temperature should be controlled below 50 °C, so that the corresponding life can be increased by about 1-2 orders of magnitude. For example, a computer capacitor that can operate for 20 years at 45 ° C can only work for 1 to 2 years at 85 ° C. If it is required to apply to the upper category temperature (85 ° C), the capacitor core center temperature should not exceed 95 ° C, and depends on the nature of the selected working electrolyte. This high temperature effect is not as severe as a solid tantalum capacitor, but it is certainly harmful.
