CharacteristicThe characteristics of electrolytic capacitor: the volume of the unit volume is very large, larger than other types of capacitors to tens of hundreds of times.
PrincipleElectrolytic capacitor is usually made of metal foil (aluminum / tantalum) as positive electrode, insulating oxide layer of metal foil (alumina / tantalum oxide five) as dielectric, electrolytic capacitors with different positive electrode for aluminum electrolytic capacitors and tantalum electrolytic capacitor. The negative electrode of aluminum electrolytic capacitor is soaked in electrolyte (liquid electrolyte) composed of thin film or polymer / electrolyte; the negative electrode of tantalum electrolytic capacitor is usually used manganese dioxide. Because the electrolyte is used as the negative electrode (the distinction between attention and dielectric), the electrolytic capacitor is named.
ApplicationThe polarity electrolytic capacitor is usually used in the power supply circuit or the intermediate frequency and low frequency circuit, such as power supply filter, decoupling, signal coupling and time constant setting, DC blocking and so on. Generally cannot be used for AC power supply circuit for filter capacitor used in DC power supply circuit, the anode (positive) should be positive end and the supply voltage is connected, the cathode (negative electrode) is connected with the negative terminal of the power supply voltage, cannot be reversed, otherwise it will damage the capacitor.
The polarity of the electrolytic capacitor, observe the electrolytic capacitors in the side "-" and "+" is the anode cathode electrolytic capacitor, if not marked on the positive and negative pole, can also be judged according to its pin length, long legs short legs is positive, negative.
In terms of current production, aluminum electrolytic capacitors account for second. This type of capacitor is the DC capacitor in general, but now, from DC to AC from low temperature to high temperature, development from low to high pressure, the development from the universal development of special type, type, structure, development from the general to the flat book type structure. Its upper limit capacity has been extended to 4F or so, the frequency has reached 30kHz, the operating temperature range has reached -55 - 125 degrees C, and some even up to 150 degrees centigrade, the rated voltage has reached 700V. In a word, the development of aluminum electrolytic capacitor is more and more widely. The reasons for these developments are as follows:
1, in the material
Aluminum foil is now used in the composition and structure are very elegant. It is no longer required for high purity, for example, for anode foils, requiring high purity to be appropriate. In order to improve the starting point, mechanical strength and the properties of the oxide film, some impurities should be included in the foil. In the structure, the low voltage foil, does not require a large proportion of cubic structure, but for high pressure foil, the structure is required to account for more than 80% of a more than 90%. On the cathode foil. In order to improve the specific requirements of grain irregular orientation impurity content of the alloy foil. There are three kinds of working electrolyte components. That is, the solute solvent and additives, such as long-term use of electrolyte, the composition of ethylene glycol, glycerol, boric acid and ammonia. Due to the development of aluminum electrolytic capacitor, the electrolyte has been far from meeting the requirements, resulting in a lot of new electrolyte, in order to reduce the capacitor temperature range (such as -55 C - L25 C). The principles of these new electrolytes are as follows: two kinds of solvents are used to complement each other. Two kinds of weak acids are used to provide the required two anionic groups. Adding alkali, such as organic amine, to adjust the pH value of the electrolyte and the flashover voltage. The improved properties of electrolyte additives, such as to prevent the aluminum oxide film hydration of phosphoric acid or its salts, hydrogen absorption of two nitrobenzene, improve ethylene oxide electrolyte sparking voltage.
2, in the process
In addition to the realization of production mechanization and automation, the process of aluminum electrolytic capacitors in the process of corrosion is the main phase of the two processes. The corrosion coefficient of Al foil has not only very high (low voltage capacitor foil has reached 100, up to 25 HP), and according to the requirements for the performance of the capacitor, different morphologies of aluminum foil corrosion pits. The corrosion process is a kind of dynamic balancing process, such as the type, concentration, temperature, original foil composition, structure, surface state, the speed of foil and the type of power supply, waveform, frequency, voltage and so on. The problem is how to get the best dynamic balance and how to determine the most balanced. Therefore, the corrosion process can not be said to have reached the best state.
Now the empowerment process has been producing dielectric oxide film quality, but also can according to different requirements, produce different dielectric oxide film, for example, the DC capacitor, produce gamma and gamma 'crystalline alumina film, the AC capacitor is amorphous film. Empowerment is the biggest progress process can be transformed into medium alumina aluminum hydroxide membrane, and can form a waterproof layer on its surface. In addition, but also can eliminate the film defects and cracks.
3, in the structure
The structure of aluminum electrolytic capacitor has been diversified, in addition to the liquid aluminum electrolytic capacitor. There are two main structural forms, one is the foil winding shape, and the other is the aluminum powder sintered porous block, the solid electrolyte is mainly MnO2. The structure of aluminum electrolytic capacitor has been diversified, such as double anode structure, cathode structure, book structure, triangular structure, chip structure. The appearance of chip aluminum electrolytic capacitor is the progress of aluminum electrolytic capacitor. Because if there is no high specific capacitance of aluminum foil, high temperature resistant electrolyte, excellent sealing structure and fine processing technology, it is difficult to produce electrolytic capacitor in line with the requirements of the chip aluminum, at present, the chip rate is still at a relatively low level.
The capsun and TDK developed the YDK-700V capacitor for the 820V material has been used in Japan capsun group's sound, this great landmark, which means that the series to 380V rectifier after coming out, 537V no longer have 2 400V. In the future, the performance of aluminum electrolytic capacitor will be further developed with the development of science and technology. 700V100uf normal capacitance is usually 35*80-100MM or 50*80-96MM price of about $22. Currently used in the world's top capsun, YAMAHA audio widely exported to Europe and the United States upscale hotels, the price of 1200 U.S. dollars to millions of dollars a set of audio expensive, mostly used in aristocratic families and hotels. The small size and large capacitance is also being developed
The test method and test conditions of the leakage current of the aluminum electrolytic capacitor are as follows: at 25 DEG C, a protective resistor connected in series with a measuring capacitor of 1000 ohms is connected with the rated voltage, and the leakage current is measured. When the applied voltage is 5 min, the leakage current shall not exceed the maximum value of the specification. Electrolytic capacitor with small capacity can be used to test results of 1min aluminum electrolytic capacitors, high-capacity aluminum will require a longer test time, the curve can be seen, the current will be infinitely close to "leakage" of the value of supply current value of medium alumina. The factor (dissipation, DF) of the electrolytic capacitor can be understood as the active power of the reactive power and the equivalent series resistance (ESR) of the electrolytic capacitor under the alternating current excitation. Obviously, this is the capacitance and equivalent series resistance (ESR) ratio. The RC circuit in AC circuits, and the ratio is very much like trigonometric function on the side near the edge of the tangent function. Therefore, the loss factor of the electrolytic capacitor (DF) also known as many in the technical literature for loss tangent. The voltage index of aluminum electrolytic capacitor is rated DC voltage, rated surge voltage, transient overvoltage and reverse voltage,
Rated DC voltage VR rated DC voltage VR is the capacitor in the rated temperature range allowed by the continuous working voltage, which includes the capacitor between the two electrodes of the DC voltage and pulse voltage or continuous pulse voltage and. Typically, the rated voltage of the tantalum capacitor is indicated on the surface of the capacitor. Usually the rated voltage is less than or equal to 100V T491B107M004AT for the "low" tantalum capacitors, and rated voltage of more than 150V high-voltage capacitor
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