An electrolytic capacitor is a polarized capacitor whose anode or positive plate is made of a metal that forms an insulating oxide layer through anodization. This oxide layer acts as the dielectric of the capacitor. A solid, liquid or gel electrolyte covers the surface of this oxide layer and acts as the cathode or negative plate of the capacitor. Due to their very thin dielectric oxide layer and enlarged anode surface, electrolytic capacitors have a much higher product of capacitance voltage (CV) per unit volume than ceramic capacitors or film capacitors, so they can have large capacitance values. There are three families of electrolytic capacitors: aluminum electrolytic capacitors, tantalum electrolytic capacitors, and niobium electrolytic capacitors.
The large capacity of electrolytic capacitors makes them especially suitable for passing or avoiding low-frequency signals and for storing large amounts of energy. They are widely used to decouple or filter noise in power supplies and DC link circuits for variable frequency drives, to couple signals between amplification stages and store energy as in a flash lamp. Electrolytic capacitors are polarized components due to their asymmetric construction and must operate with a higher voltage (that is, more positive) at the anode than at the cathode at all times. For this reason, the anode terminal is marked with a plus sign and the cathode with a minus sign. Applying a reverse polarity voltage, or a voltage that exceeds the maximum rated working voltage of just 1 or 1.5 volts, can destroy the dielectric and therefore the capacitor. Electrolytic capacitor failure can be dangerous and cause an explosion or fire. Bipolar electrolytic capacitors are also manufactured that can operate with any polarity, using special constructions with two anodes connected in series. A bipolar electrolytic capacitor can also be made by connecting two normal electrolytic capacitors from anode to anode or from cathode to cathode.
These are used in current feeder filters, where they are used to store the load, and stabilize and / or filter the electrical output voltage, reducing the ripple of the alternating component and the current fluctuations in the rectified output. They are also widely used in circuits that must conduct direct current but not alternating current.
Electrolytic capacitors can have a lot of capacity, allowing the construction of very low frequency filters
There are several types of electrolytic capacitors such as: