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Why can't aluminum electrolytic capacitance withstand reverse voltage? - News

Why can't aluminum electrolytic capacitance withstand reverse voltage?

280 Published by http://weixin.sogou.com/ at February 24,2018

We all know that capacitors have always played a very important role in electronic circuits, in which they are responsible for the differential characteristics of volt-ampere characteristics in the coupled RC circuits of signals, such as integrals. Aluminum electrolytic capacitor consists of anodic aluminum foil which is corroded and formed oxide film, and cathodic aluminum foil that is corroded. Then sealed in an aluminum shell.

So why can't aluminum electrolyte capacitance withstand reverse voltage?

Due to the polarity of electrolytic capacitor, we must pay attention to the correct connection method of positive and negative electrode in use, otherwise, not only the capacitor can not play a role, but also the leakage current is very large. In a short time, the inside of the capacitor will heat up, destroy the oxide film, and then damage.

The basic structure of the aluminum electrolytic capacitor, which consists of the anode, the aluminum layer formed by alumina attached to the insulating medium, the cathode aluminum layer of the receiving pole, The electrolyte is immersed on the paper between two aluminum layers. The alumina layer is electroplated on the aluminum layer, which is very thin relative to the voltage added on it and is easily broken down, resulting in capacitor failure.

The alumina layer can withstand a forward DC voltage, and if it has a reverse DC voltage, it can easily fail in seconds. This phenomenon is called 'Valve Effect', which is why aluminum electrolytic capacitors have polarity. If there is an oxide layer on both electrodes of the electrolytic capacitance, a non-polar capacitor is formed.

Many articles reported the phenomenon of threshold mechanism of aluminum electrolytic capacitor of reverse voltage, called the theory of hydrogen ion, when the electrolytic capacitor under reverse DC voltage, the cathode electrolyte under positive voltage and negative voltage withstand oxidation layer, hydrogen ions in the oxide layer will be set through the medium to medium and metal the boundary layer, into hydrogen, hydrogen oxidation layer expansion force makes off, so the current direct circulation capacitor breakdown in electrolyte capacitor failure, the DC voltage is very small, the direct current voltage in the reverse 1~2V, aluminum electrolytic capacitor In a few seconds, the hydrogen ion effect causes immediate invalidation. On the contrary, when the electrolytic capacitance is subject to a forward voltage, the negative ions are concentrated between the oxide layers, because the anion is so large in diameter that it does not break through the oxide layer. So it can withstand higher voltage.

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