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capacitors
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RCD snubber design based on reliability consideration: A case study for thermal balancing in power electronic converters
, Article Microelectronics Reliability ; Volume 88-90 , 2018 , Pages 1311-1315 ; 00262714 (ISSN) ; Zarghani, M ; Kaboli, S ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In a turn-off RCD snubber, the capacitor value is usually optimized in order to minimize the power dissipated in the switch and snubber circuit. However, it may not be the best value of the snubber capacitor from the reliability point of view. In this paper, the capacitor value is optimized based on reliability considerations. Proposed method presents a new design to achieve the maximum reliability for the set of switch and its snubber. Mathematical analysis of the proposed method is conducted in MATLAB environment. Also, the experimental results are presented for validity of the theoretical analysis. © 2018 Elsevier Ltd
Precise formulation of electrical capacitance for a cylindrical capacitive sensor
, Article Journal of Applied Sciences ; Volume 9, Issue 8 , 2009 , Pages 1556-1561 ; 18125654 (ISSN) ; Golnabi, H ; Sharif University of Technology
2009
Abstract
In this study a more precise formulation of electrical capacitance for a cylindrical capacitive sensor is reported. By using different theoretical models such as Coulomb law, Gauss law and Laplace equation the electrical capacitance is calculated. Based on the given models the relation between the capacitance and the geometrical parameters (e.g., cylindrical length) is formulated and by using suitable software capacitance variation is computed and compared for different methods. In Coulomb method, the electrical potential is first solved numerically by using Mathematica and then the electrical capacitance is computed. It is found that the active capacitor length is crucial parameter in the...
Low-noise differential transimpedance amplifier structure based on capacitor cross-coupled gm-boosting scheme
, Article Microelectronics Journal ; Volume 39, Issue 12 , 2008 , Pages 1843-1851 ; 00262692 (ISSN) ; Nabavi, A ; Moravvej Farshi, M. K ; Fotowat Ahmady, A ; Sharif University of Technology
2008
Abstract
This paper presents a capacitor cross-coupled gm-boosting scheme for differential implementation of common-gate transimpedance amplifier (CG-TIA). A differential transimpedance amplifiers (DTIA) is designed by this scheme using two modified floating-biased CG stage with improved low corner frequency. Despite conventional methods for single-ended to differential conversion that increase the power and the noise for the same gain, the new DTIA gives a higher gain and hence reduces the input-referred noise power. Design of the DTIA circuit using 0.13 μm CMOS technology illustrates near 1.7 dB improvement in the circuit sensitivity and 5.2 dB enhancement in transimpedance gain compared to its...
Theoretical analysis of the performance of a model supercapacitor consisting of metal oxide nano-particles
, Article Journal of Solid State Electrochemistry ; Volume 11, Issue 8 , 2007 , Pages 1085-1092 ; 14328488 (ISSN) ; Gobal, F ; Sharif University of Technology
2007
Abstract
The factors influencing the electrochemical behaviour of a supercapacitor have been partly examined in this work. The effects of so-called intrinsic parameters, i.e. exchange current density, unit cell length and double layer (DL) capacitance; as well as the so-called application parameters, i.e. cell current, on the cell potential discharge time have been considered. The contributions of each type of capacitors, DL capacitor and faradaic supercapacitor under various states of operation and material have been analyzed, and the competing (compensating) effects of the two types of capacitors as regards to the discharge and power characteristics manifested by current-potential and energy-power...
Theoretical investigation of dielectric corona pre-ionization TEA nitrogen laser based on transmission line method
, Article Optics and Laser Technology ; Volume 39, Issue 5 , 2007 , Pages 1014-1019 ; 00303992 (ISSN) ; Fallah, R ; Ganjovi, A. R ; Bahrampour, A ; Sharif University of Technology
2007
Abstract
This paper models the dielectric corona pre-ionization, capacitor transfer type of flat-plane transmission line traveling wave transverse excited atmospheric pressure nitrogen laser by a non-linear lumped RLC electric circuit. The flat-plane transmission line and the pre-ionizer dielectric are modeled by a lumped linear RLC and time-dependent non-linear RC circuit, respectively. The main discharge region is considered as a time-dependent non-linear RLC circuit where its resistance value is also depends on the radiated pre-ionization ultra violet (UV) intensity. The UV radiation is radiated by the resistance due to the surface plasma on the pre-ionizer dielectric. The theoretical predictions...
Effects of the electric field configuration's variation due to micro-cantilever beam's curvature on pull-in phenomenon
, Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 1096665X (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2006
Abstract
Micro-electromechanical systems (MEMS) have wide application in the development of sensors for the detection of magnitudes in almost any domain [1]. Resonant mode operation of micro and nano-scale oscillators have gained wide interest for applications including filters, amplifiers, non-linear mixers, atomic scale imaging, biological and chemical sensors. The device that we propose is an electrically actuated microcantilever beam. More precisely, in our design the microcantilever constitutes the movable plate of a micro-capacitor and its displacement is controlled by the voltage applied across the plates. Review of literature shows that the electric field pattern between the beam and the...
A genetic based method for optimal reactive power compensation of transmission network
, Article Australian Journal of Electrical and Electronics Engineering ; Volume 3, Issue 1 , 2006 , Pages 47-55 ; 1448837X (ISSN) ; Vakilian, M ; Sharif University of Technology
Institution of Engineers (Australia)
2006
Abstract
Reactive power compensation is known as an effective tool to overcome the violations of voltage limits in electric power systems. It is also deployed to be an efficient method to minimise transmission losses. In order to maximize the effectiveness of reactive power compensation, VAr sources of proper sizes should be placed at some network buses. In this paper, a new VAr expansion tool has been developed to improve the voltage profile and reduce MW losses in a bulk power network. Keeping the minimum expansion cost and minimum switching of capacitor banks during change of load level of the system are emphasized in the proposed method. This method is based on application of genetic algorithm in...
A geometric approach to fault detection and isolation in a grid-connected inverter
, Article IEEE Transactions on Control Systems Technology ; Volume 29, Issue 6 , 2021 , Pages 2622-2629 ; 10636536 (ISSN) ; Namvar, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
We present a nonlinear geometric approach to fault detection and isolation (FDI) in a grid-connected inverter system. Open-switch faults in inverter power transistors together with faults in grid voltages and source current sensors are detected and isolated in the presence of disturbance. The detection process is based on dynamic model of an inverter, including a dc-bus capacitor and an output $RL$ filter. The proposed FDI system does not rely on balanced or zero-sum conditions in the grid point and is functional under nonsinusoidal voltages and currents. © 1993-2012 IEEE
A voltage balancing scheme for series igbts to increase their expected lifetime in pulsed load applications
, Article IEEE Journal of Emerging and Selected Topics in Power Electronics ; Volume 9, Issue 1 , 2021 , Pages 461-471 ; 21686777 (ISSN) ; Zarghani, M ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
Clamp mode resistor capacitor diode (CMRCD) snubbers have a simple and easy implementing structure. They have been widely adopted in the pulsed power supplies to provide a safe operating condition for the series insulated gate bipolar transistors (IGBTs). The main problem of the CMRCD snubbers is their poor performance in the voltage balancing of the series IGBTs. They are essentially overvoltage protectors and clamp the voltage of the IGBTs in a probable potentially dangerous condition. This issue diminishes the expected lifetime of the series IGBTs, where a number of them face a higher level of the voltage than that of the others. The unbalanced voltage of the series IGBTs will result in a...
Reactive compensation techniques for increasing loadability of long primary distribution lines
, Article 37th Annual North American Power Symposium, 2005, Ames, IA, 23 October 2005 through 25 October 2005 ; Volume 2005 , 2005 , Pages 233-237 ; 0780392558 (ISBN); 9780780392557 (ISBN) ; Stefopoulos, G. K ; Parniani, M ; Sharif University of Technology
2005
Abstract
Electric networks often consist of remote cities or villages with low population densities, which consume a considerably small amount of energy. This can be in the order of a few megawatts for places that are up to 100 km away from the source. Typical uncompensated primary distribution lines are not an effective option for these situations, since line loadability drastically decreases as the line length is increased. Increasing the voltage level, on the other hand, is not cost effective. This paper investigates different reactive compensation techniques for increasing the loadability of these lines. Effect of series capacitors, shunt capacitors and voltage regulating transformers in such...
Electrical properties of nanocontacts on silicon nanoparticles embedded in thin SiO2 synthesized by ultralow energy ion implantation
, Article Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures ; Volume 23, Issue 6 , 2005 , Pages 2821-2824 ; 10711023 (ISSN) ; Shalchian, M ; Coffin, H ; Claverie, A ; Grisolia, J ; Dumas, C ; Atarodi, S. M ; Sharif University of Technology
2005
Abstract
In this paper, we present the room temperature current-voltage characteristics of large (100×100 μ m2) and a nanoscale (100×100 nm2) metal-oxide-semiconductor (MOS) capacitor containing few silicon nanocrystals. The layer of silicon crystals is synthesized within the oxide of this capacitor by ultralow energy ion implantation and annealing. Current fluctuations in the form of discrete current steps and sharp peaks are apparent in the static and dynamic I (V) characteristics of the capacitor. These features have been associated to quantized charging and discharging of the nanoparticles and the resulting Coulomb interaction to the tunneling current. © 2005 American Vacuum Society
An enhanced dynamic range low-power delta-sigma modulator for portable voice band applications
, Article 2003 Southwest Symposium on Mixed-Signal Design, SSMSD 2003, 23 February 2003 through 25 February 2003 ; 2003 , Pages 263-268 ; 0780377788 (ISBN); 9780780377783 (ISBN) ; Aslanzadeh, H. A ; Mehrmanesh, S ; Vahidfar, M. B ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2003
Abstract
A new second order sigma delta modulator with the reduced number of op-amps, to decrease static power consumption and area, is presented for voice band applications such as codecs. This switched capacitor modulator uses reused capacitor technique to reduce the input thermal noise and circuit area. It improves the DR of modulator by almost 0.5 bit. The modulator shows 87 dB DR for voice band while consuming 125 μW from a 2.5 V supply. © 2003 IEEE
Accurate fault location algorithm for series compensated transmission lines
, Article IEEE Transactions on Power Delivery, Piscataway, NJ, United States ; Volume 15, Issue 3 , 2000 , Pages 1027-1033 ; 08858977 (ISSN) ; Hadjsaid, N ; Ranjbar, A. M ; Feuillet, R ; Sharif University of Technology
IEEE
2000
Abstract
In this paper, an accurate fault location algorithm for series compensated power transmission lines is presented. Distributed time domain model is used for modeling of the transmission lines. The algorithm makes use of two subroutines for estimation of the fault distance - one for faults behind the series capacitors and another one for faults in front of the series capacitors. Then a special procedure to select the correct solution is utilized. Samples of voltages and currents at both ends of the line are taken synchronously and used to calculate the location of the fault. The proposed algorithm is independent of fault resistance and does not require any knowledge of source impedance. The...
MnO2/ordered mesoporous carbon nanocomposite for electrochemical supercapacitor
, Article Journal of Solid State Electrochemistry ; Vol. 18, issue. 4 , 2014 , pp. 1117-1125 ; Khani, H ; Mohammadi, N ; Sharif University of Technology
Abstract
The preparation of composite manganese dioxide (MnO2) nanoparticles in an ordered mesoporous carbon (CMK-3) matrix and its use for constructing a new wide-potential-window supercapacitor is reported. CMK-3 is prepared using mesoporous silica as a hard template and sucrose as carbon source. The different ratios of MnO2/CMK-3 composite is synthesized by impregnating CMK-3 with a Mn(NO3)2·4H 2O solution followed by annealing in nitrogen. Physical properties, morphology, and specific surface area were characterized by X-ray diffraction, transmission electron microscopy, and nitrogen sorption measurements, respectively. The electrochemical properties of the composite were studied by cyclic...
A control method for integrating hybrid power source into an islanded microgrid through CHB multilevel inverter
, Article PEDSTC 2013 - 4th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2013 , Pages 495-500 ; 9781467344845 (ISBN) ; Hamzeh, M ; Mokhtari, H ; Sharif University of Technology
2013
Abstract
This paper proposes a control strategy for an islanded microgrid to effectively coordinate hybrid power source (HPS) units and to robustly control individual interfaced inverters under unbalanced and nonlinear load conditions. Cascaded H-bridge (CHB) multilevel inverters are flexibly deployed in order to enhance the power quality and redundancy. The HPS employs fuel cell (FC) as the main and supercapacitors (SC) as complementary power sources. Fast transient response; high performance; and high power density are the main characteristics of the proposed HPS system. The presented control strategy consists of a power management strategy for the HPS units and a voltage control strategy for the...
A low power, eight-phase LC-ring oscillator for clock and data recovery application
, Article 2012 Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits, INMMIC 2012 ; 2012 ; 9781467329491 (ISBN) ; Hajsadeghi, K ; Sharif University of Technology
2012
Abstract
A four stage LC-ring oscillator is presented. Eight different phases are generated in which there in 45 degrees phase difference between consecutive outputs and direction of phases is defined. Nmos capacitors in parallel with constant capacitors are used for coupling between stages. The control voltage is applied to Pmos varactors to adjust the oscillation frequency. The advantages of this structure are the rather small inductors size, low power consumption, and tuning curve linearity. The proposed structure is simulated in 0.18um CMOS technology. Power consumption for each stage is 4.8mW from a 1.8B supply. The proposed VCO has a phase noise of -121dBc/Hz at 1MHz offset from the center...
A new class AB multipath telescopic-cascode operational amplifier
, Article ICEE 2012 - 20th Iranian Conference on Electrical Engineering, 15 May 2012 through 17 May 2012 ; May , 2012 , Pages 74-76 ; 9781467311489 (ISBN) ; Hajsadeghi, K ; Sharif University of Technology
2012
Abstract
A novel class AB architecture for single stage multipath differential amplifier is presented. The proposed amplifier combines the flipped voltage follower(FVF) for differential input and the nonlinear current mirror for active load. Applying these techniques to telescopic-cascode amplifier increases the unity-gain bandwidth, the DC gain and the slew rate while the same power consumption as the conventional telescopic cascade is achieved
A lifetime improved single phase grid connected photovoltaic inverter
, Article 2012 3rd Power Electronics and Drive Systems Technology, PEDSTC 2012, 15 February 2012 through 16 February 2012 ; February , 2012 , Pages 234-238 ; 9781467301114 (ISBN) ; Tahami, F ; Sharif University of Technology
2012
Abstract
In this paper, a reliable low power single phase grid-connected inverter for photovoltaic modules is proposed. The inverter has improved lifetime since large electrolytic capacitor is replaced with small film capacitor due to circuit topology, power processing and proper control scheme. Thus the main limiting component in single phase grid connected inverters is obviated. The proposed inverter consists of two power processing stages. First a dual active bridge (DAB) converter boosts the voltage of PV panel to approximately 440 V and eliminates impact of high dc bus voltage ripples. A proper feed forward control is proposed to regulate the dc bus voltage with high ripple. Simulation results...
A comparative study of sequentially layer-deposited and co-deposited Co-Mn oxides as potential redox capacitors
, Article Journal of Solid State Electrochemistry ; Volume 16, Issue 4 , April , 2012 , Pages 1561-1569 ; 14328488 (ISSN) ; Jafarzadeh, S ; Sharif University of Technology
2012
Abstract
Layers of cobalt and manganese oxides were co-deposited or deposited on top of each other or next to each other by potentiostatic method onto stainless steel substrate. Deposition potentials of 1 and -1 V for the anodic and cathodic depositions were employed. Specific capacitance values in the range of 38.5-78 F g -1 were found with cobalt oxide on top of manganese oxide having the lowest and manganese oxide on top of cobalt oxide having the highest capacitances. The usefulness of the electrodes was characterized by cyclic voltammetry, charge-discharge cycling, and electrochemical impedance spectroscopy in 2 M NaOH electrolyte for redox supercapacitor applications. The latter presented the...
A low power 1-V 10-bit 40-MS/s pipeline ADC
, Article 2011 18th IEEE International Conference on Electronics, Circuits, and Systems, ICECS 2011, 11 December 2011 through 14 December 2011 ; December , 2011 , Pages 212-215 ; 9781457718458 (ISBN) ; Sharifkhani, M ; Gholami, M ; Sharif University of Technology
2011
Abstract
A low power 10 bit, 40 MS/s pipeline analog to digital converter is presented. A number of low-power techniques are proposed in various levels of abstraction. In circuit level, a low power class A/AB opamp with direct common-mode-feedback circuit (CMFB) is proposed which significantly reduces power in the opamps. In backend design, optimal series capacitors are layed out to break the deadlock between the mismatch and loading effect of the first stage capacitors. A customized software tool is developed based on the proposed opamp and architecture which provides optimum stage scaling factors, tail current and opamp transistor sizes. Simulations in 0.13um CMOS technology show that the ADC...