Niobium electrolytic capacitors use a sintered "slug" of high-purity niobium or niobium oxide powder with niobium pentoxide as dielectric.Tantalum electrolytic capacitors use a sintered pellet (“slug”) of high-purity tantalum powder with tantalum pentoxide as dielectric.Aluminum electrolytic capacitors use a high-purity etched aluminium foil with aluminium oxide as dielectric.There are three different anode metals in use for electrolytic capacitors: Each of these three capacitor families uses non-solid and solid manganese dioxide or solid polymer electrolytes, so a great spread of different combinations of anode material and solid or non-solid electrolytes is available.īasic principle of anodic oxidation (forming), in which, by applying a voltage with a current source, an oxide layer is formed on a metallic anodeĮlectrolytic capacitors use a chemical feature of some special metals, previously called "valve metals", which on contact with a particular electrolyte form a very thin insulating oxide layer on their surface by anodic oxidation which can function as a dielectric. General information Electrolytic capacitors family tree Īs to the basic construction principles of electrolytic capacitors, there are three different types: aluminum, tantalum, and niobium capacitors. 5.3 Failure modes, self-healing mechanism and application rules.4.10 Current surge, peak or pulse current.4.2 Capacitance, standard values and tolerances.2.3 Styles of aluminum and tantalum electrolytic capacitors.2.2 Comparison of electrical parameters.2.1 Comparison of electrolytic capacitor types.2 Types and features of electrolytic capacitors.1.6 Basic construction of solid tantalum electrolytic capacitors.1.5 Basic construction of non-solid aluminum electrolytic capacitors.1.4 Capacitance and volumetric efficiency.1.1 Electrolytic capacitors family tree.A bipolar electrolytic capacitor can also be made by connecting two normal electrolytic capacitors in series, anode to anode or cathode to cathode. Bipolar electrolytic capacitors which may be operated with either polarity are also made, using special constructions with two anodes connected in series. The failure of electrolytic capacitors can be hazardous, resulting in an explosion or fire.
Applying a reverse polarity voltage, or a voltage exceeding the maximum rated working voltage of as little as 1 or 1.5 volts, can destroy the dielectric and thus the capacitor.
For this reason the polarity is marked on the device housing. They are widely used for decoupling or noise filtering in power supplies and DC link circuits for variable-frequency drives, for coupling signals between amplifier stages, and storing energy as in a flashlamp.Įlectrolytic capacitors are polarized components due to their asymmetrical construction and must be operated with a higher potential (ie, more positive) on the anode than on the cathode at all times. The large capacitance of electrolytic capacitors makes them particularly suitable for passing or bypassing low-frequency signals, and for storing large amounts of energy. There are three families of electrolytic capacitor: aluminum electrolytic capacitors, tantalum electrolytic capacitors, and niobium electrolytic capacitors. Due to their very thin dielectric oxide layer and enlarged anode surface, electrolytic capacitors have a much higher capacitance- voltage (CV) product per unit volume than ceramic capacitors or film capacitors, and so can have large capacitance values. A solid, liquid, or gel electrolyte covers the surface of this oxide layer, serving as the cathode or negative plate of the capacitor. This oxide layer acts as the dielectric of the capacitor. For other types of polarized capacitors, see Supercapacitor.Īn electrolytic capacitor is a polarized capacitor whose anode or positive plate is made of a metal that forms an insulating oxide layer through anodization.
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