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The correct selection of Capacitor in Modern Power supply Technology(III)

Views: 0     Author: Site Editor     Publish Time: 2018-03-22      Origin: Site

Voltage and life test


A factor of safety is left between the rated voltage and the breakdown voltage of the capacitor, such as a 400V electrolytic capacitor with a breakdown voltage of not less than 450 V and a film capacitor with a breakdown voltage of 1.5 to 2 times the rated voltage, Therefore, it cannot be said that the capacitor may break down when it reaches the rated voltage.

The life test of thin film capacitor is to apply 1.5 times rated voltage at its highest working temperature to ensure that it will not be damaged within 500h or 1000h. The life test of electrolytic capacitor is that under the condition of the highest working temperature and rated voltage, the main parameters of the electrolytic capacitor meet the prescribed requirements during the rated life period.


The life of electrolytic capacitor is directly related to the ambient temperature of the capacitor working for a long time. The higher the temperature, the shorter the life of capacitor. Common electrolytic capacitors have been damaged at ambient temperature of 90 ℃, such as 1: B41303 / B43303 type electrolytic capacitors. However, there are many kinds of electrolytic capacitors with high ambient temperature. For example, B43502 is at 90 ℃, and the ratio of AC current to rated pulse current through electrolytic capacitor is 0.5. The lifetime is still 10, 000 h, but if the temperature rises to 95 ℃, the electrolytic capacitor is damaged. Therefore, when selecting capacitors, we should select them according to specific ambient temperature and other parameters. If the influence of ambient temperature on capacitor life is ignored, the reliability and stability of power supply will be greatly reduced. Even damaged equipment and equipment. Generally speaking, the electrolytic capacitor can reach the requirement of 10000h life when the ambient temperature is 80 ℃.

On the other hand, the life of the electrolytic capacitor is also associated with the AC current and rated pulse current of the capacitor operating for a long time (usually measured at an ambient temperature of 85 ℃), But there are some high temperature resistant electrolytic capacitors that are measured at 125 ℃) of the ratio. In general, the larger the ratio, the shorter the life of the electrolytic capacitor. When the current passing through the electrolytic capacitor is 3.8 times the rated current, the electrolytic capacitor is generally damaged.


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