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PatchAluminum Electrolytic capacitorWhen used in pulsating circuits, the main factor that causes power consumption and heating is the ripple current (ripple voltage for capacitors with smaller capacity). Generally, the relationship curve between Failure rate and temperature is measured under DC voltage without ripple, only considering the leakage current, which is almost the same as the temperature in the center of the core and the ambient temperature at this time.
However, in practical applications, the heating caused by the ripple current can cause the center temperature of the core to rise, reaching a maximum of tens of degrees Celsius. (The core temperature rise depends on the ambient temperature of the Electrolytic capacitor and the control of ripple current). Therefore, high ripple currents can easily cause the electrolyte of the core to dry up, leading to early failure of the capacitor. Meanwhile, prolonged ripple current exceeding the specified value is also one of the factors leading to the opening of the capacitor explosion-proof valve.
2. Choose capacitors with lower leakage current values
As a long-life Electrolytic capacitor, in addition to the consideration of the above four external factors, capacitors of the same type with very small leakage current should also be selected. This indicates that it has a high-quality oxide film and suitable working electrolyte. Once the ambient temperature is high, the corresponding leakage current increases slowly. Otherwise, under the condition of mutual influence, when the leakage current sharply increases, the internal temperature will rise, which in turn will make the leakage current rise again, and it will deteriorate until the Thermal equilibrium is lost and destroyed.
3. Reduce the upper limit of rated voltage usage
Reducing the upper limit of the rated voltage, that is, reducing the working field strength of the dielectric oxide film, will be applicable to Electrolytic capacitor. After reducing the load by half, the lifespan of the capacitor can be increased by up to two orders of magnitude.
In fact, if the aluminum oxide film is damaged and corroded, the repair oxidation worship can only be carried out at the highest working voltage, and it is difficult to restore the thickness of the oxide film at the original formation voltage locally, so excessively reducing the working voltage is not the most appropriate measure for Aluminum electrolytic capacitor.
4. Reduce ambient temperature
Reduce the ambient temperature so that the Electrolytic capacitor does not work at the upper limit temperature. In addition, consider the heating effect of the capacitor itself, which is particularly important for liquid electrolyte products. If high temperatures are generated, it will cause a sharp increase in leakage current and gas, causing the shell to be in a state of rapid internal pressure increase; In addition, high temperature can accelerate the drying of the electrolyte, which relatively shortens the product life.
Therefore, for the Electrolytic capacitor with long service life requirements, the working temperature should be controlled below 50 ℃, so that the corresponding service life can be increased by 1~2 orders of magnitude. For example, a computer capacitor that can work for 20 years at 45 ℃ can only work for 1-2 years at 85 ℃. If it needs to be applied at the upper limit category temperature (85 ℃), the center temperature of the capacitor core should not exceed 95 ℃, and it depends on the properties of the selected working electrolyte. This high temperature effect on solid tantalum capacitors is not as serious as Aluminum electrolytic capacitor, but it is certainly harmful.