China
Africa
Explore chapters and articles related to this topic
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
There are two main classes of capacitors - electrolytic and electrostatic. Electrolytic capacitors include aluminum and tantalum types, used in applications where large capacitance values are needed. Electrostatic capacitors include plastic, ceramic disk, ceramic chip, mica, and glass. Aluminum electrolytics are constructed from high-purity aluminum foils that are chemically etched to increase the surface area, then anodized to form the dielectric. The thickness of this anodized layer determines the voltage rating of the capacitor. If only one foil is anodized, the capacitor is a polarized unit, and the instantaneous voltage cannot be allowed to reverse polarity. Porous paper separates the two foils and is saturated with a liquid electrolyte; therefore, the unit must be sealed, and leakage is a common failure mode. During extended periods of storage, the anodized layer may partially dissolve, requiring the unit to be reformed before rated voltage can be applied. Aluminum electrolytics exhibit a large series inductance, which limits the useful range of frequencies to about 20kHz. They also have a large leakage current. Nevertheless, because of low cost and very large values of capacitance (up to 1F), they are a popular choice for filtering applications.
Electric Circuits and Components
Published in Quamrul H. Mazumder, Introduction to Engineering, 2018
The second most commonly used capacitor type is the electrolytic capacitor that consists of three subtypes: tantalum, aluminum, and niobium. The dielectric is made using tantalum, aluminum, or niobium plates to sandwich a semiliquid borax electrolyte paste. Among the three subtypes, the ones most commonly used are tantalum and aluminum. Tantalum capacitors generally reach up to 1000 µF, whereas aluminum capacitors can go as high as a few hundred millifarads. Tantalum capacitors, unlike aluminum capacitors, have more stable characteristics due to lower losses, and are often used in circuits with high-precision requirements. On the other hand, aluminum capacitors are typically used in power supplies and motor drive circuits for filtering, coupling, and bypassing signal noise.
Nanoengineered Material Applications in Electronics, Biology, and Energy Harnessing
Published in Anupama B. Kaul, Microelectronics to Nanoelectronics, 2017
Daniel S. Choi, Zhikan Zhang, Naresh Pachauri
Capacitors (formerly known as condensers) store electric energy charges and release them as needed. Traditional electrolytic capacitors work by utilizing two conducting plates (usually made of metals that are capable of being charged) and a thin film dielectric (insulating material) as a separator in an electrolyte. The amount of capacitance that can be achieved is described in this simple equation: Capacitance = dielectric constant of medium × area of plate/distance between platesLeonard et al. (2009) have demonstrated high electrostatic double layer (EDL) capacity with porous carbon supports as well as the potential that is developed on the insulating oxides. The difference here is that most of the charge is stored by the insulating film of nanoparticulate insulating oxides. The charge on the oxide is developed by a potential determining ion such as a proton.
New DC Hybrid Filter for Attenuating Low-Frequency Ripple of AC-DC Power Converter
Published in Electric Power Components and Systems, 2019
Jinn-Chang Wu, Hurng-Liahng Jou, Tse-Yu Lin
Electrolytic capacitors are generally acting as the energy buffer due to advantages of high energy density and low cost. However, electrolytic capacitors incur significant reliability problems due to the increasing ESR and the decreasing the capacitance with age. Accordingly, the most serious problem affecting the reliability of AC-DC power converter is the DC bus capacitor. A new DC hybrid power filter is proposed for replacing the electrolytic capacitor in this article. The feedforward control is used to control the DC hybrid power filter to simplify the control circuit as compared with the controller used in the conventional active decoupling circuits. The experimental results, verify that the DC hybrid power filter has superior performance in suppressing the twice-utility frequency ripple of output voltage under the steady state and transient state. In addition, the proposed DC hybrid power filter can also improve the transient response of AC-DC power converter because of the reduction of DC bus capacitor. The proposed DC hybrid power filter can also be applied to be the power conversion interface between a single-phase utility and a DC microgrid to attenuate the pulsation power of twice-utility frequency. Additionally, the DC hybrid power filter is also suitable to be used in the applications of DC microgrid to protect the power sources, such as battery set and fuel cell, from the low-frequency current harmonics.
Battery energy storage system with functions of wide AC voltage range and battery current filtering
Published in International Journal of Electronics, 2022
Jinn-Chang Wu, Hurng-Liahng Jou, You-Chen Ji
The power stored in a battery set is the DC power; however, the AC distribution power system is popular worldwide. Therefore, incorporating the battery set into the grid must rely on a power conversion interface for AC-DC and DC-AC power conversion (Chen et al., 2020; Hashempour et al., 2019; Lamsal et al., 2019; H. Liu et al., 2017; Manandhar et al., 2019; Morstyn et al., 2018; Rocabert et al., 2019; Wang et al., 2019; Wu et al., 2019; Yang et al., 2018; Zhang et al., 2019). The nominal voltage of single-phase grid in each country is different. For example, the nominal voltage of single-phase grid is 100 V/200 V in Japan, 110 and 220 V in Taiwan, 120 and 240 V in United States. For satisfying the AC voltage in different countries, the amplitude range of the AC voltage for single-phase power conversion interface should be wide (Fan et al., 2019; Ham et al., 2018). In general, the DC bus voltage of single-phase power conversion interface is designed to be larger than the peak of maximum single-phase grid voltage. This results in the larger power loss in the lower single-phase grid voltage. Besides, the double-frequency instantaneous power injection on the DC side regardless of the direction of power conversion occurs in the single-phase power conversion. Therefore, in the applications of single-phase BESS, a large double-frequency ripple current will be generated to charge/discharge the battery set. Conventionally, a large-capacity electrolytic capacitor is connected in parallel on the DC terminal of the single-phase power conversion interface to filter out the double-frequency ripple. However, its filtering characteristic is degraded due to the large equivalent resistance of the electrolytic capacitor. In addition, the short life of the electrolytic capacitor affects the reliability of the power conversion interface (Barth et al., 2019). Therefore, several DC active filter technologies have been developed to replace the electrolytic capacitor (Bhowmick & Umanand, 2018; Li et al., 2016; W. Liu et al., 2015; Wu, Jou, Wu et al., 2020). In (W. Liu et al., 2015), a series type DC active filter is configured by inserting a power converter between the AC-DC power converter and the DC load, where the power converter generates a voltage to eliminate the double-frequency ripple of output voltage of the AC-DC power converter. The power converter can also be connected in parallel to the output of AC-DC power converter to form a parallel type DC active filter to generate a double-frequency instantaneous power and thus attenuates the double-frequency ripple of output voltage of the AC-DC power converter (Bhowmick & Umanand, 2018; Li et al., 2016; Wu, Jou, Wu et al., 2020).