Showing papers on "Equivalent circuit published in 2008"

A Real-Time Voltage Instability Identification Algorithm Based on Local Phasor Measurements

Abstract: This paper proposes a new voltage instability risk indicator based on local phasor measurements at fast sampling rate. The effectiveness of the indicator is analyzed at EHV load and ldquotransitrdquo buses. The risk criterion is based on the real-time computation of the Thevenin equivalent impedance of the classic electrical circuit given by an equivalent generator connected to an equivalent load impedance through an equivalent connecting impedance. The main contribution of the paper is the innovating algorithm utilized on the real-time adaptive identification of the Thevenin voltage and impedance equivalents. The algorithm performance is shown through a detailed sensitivity analysis. The paper presents important numerical results from the actual Italian EHV network.

Extraordinary Transmission Through Arrays of Electrically Small Holes From a Circuit Theory Perspective

Abstract: Extraordinary optical transmission of light or electromagnetic waves through metal plates periodically perforated with subwavelength holes has been exhaustively analyzed in the last ten years. The study of this phenomenon has attracted the attention of many scientists working in the fields of optics and condensed matter physics. This confluence of scientists has given rise to different theories, some of them controversial. The first theoretical explanation was based on the excitation of surface plasmons along the metal-air interfaces. However, since periodically perforated dielectric (and perfect conductor) slabs also exhibit extraordinary transmission, diffraction by a periodic array of scatterers was later considered as the underlying physical phenomenon. From a microwave engineering point of view, periodic structures exhibiting extraordinary optical transmission are very closely related to frequency-selective surfaces. In this paper, we use simple concepts from the theory of frequency-selective surfaces, waveguides, and transmission lines to explain extraordinary transmission for both thin and thick periodically perforated perfect conductor screens. It will be shown that a simple transmission-line equivalent circuit satisfactorily accounts for extraordinary transmission, explaining all of the details of the observed transmission spectra, and easily gives predictions on many features of the phenomenon. Although the equivalent circuit is developed for perfect conductor screens, its extension to dielectric perforated slabs and/or penetrable conductors at optical frequencies is almost straightforward. Our circuit model also predicts extraordinary transmission in nonperiodic systems for which this phenomenon has not yet been reported.

Full-Wave Modal Dispersion Analysis and Broadside Optimization for a Class of Microstrip CRLH Leaky-Wave Antennas

Abstract: In this paper, a planar microstrip composite right/left-handed leaky-wave antenna is analyzed and designed as an infinite 1-D periodic microstrip leaky-wave antenna. A parametric study, based on a full-wave numerical modal approach that analyzes a unit cell using a periodic layered-medium Green's function, is shown to be an efficient approach to accurately design the structure, completely eliminating open-stopband effects and achieving an almost constant radiation efficiency when the beam is scanned through broadside. Results obtained by the proposed approach are compared with those obtained by means of both an artificial transmission-line analysis and a Bloch-wave analysis, which use the full-wave simulation of a finite-length structure. The balanced condition is interpreted in terms of the behavior of the phase and attenuation constants relevant to the radiating harmonic. Furthermore, it is shown how radiation at broadside is guaranteed by the presence of two radiating elements (one series and one shunt) within the equivalent circuit of the unit cell. The effectiveness of the analysis is demonstrated through the design of a finite-length antenna excited by a source at one end.

Multimodal system for harvesting magnetic and mechanical energy

Abstract: In this letter, we investigate a multimodal system for simultaneous energy harvesting from stray magnetic and mechanical energies by combining magnetoelectric and piezoelectric effects. The system consists of a cantilever beam with tip mass and a magnetoelectric laminate attached in the center of the beam. At 2 Oe magnetic field and mechanical vibration amplitude of 50mg, both at frequency of 20 Hz, the system was found to generate open circuit output voltage of 8 VP.P.. An equivalent circuit model is proposed that predicts a summation effect for both mechanical and magnetic energies.

Power Supply for a High-Voltage Application

Abstract: In this paper, the guidelines to design a high-voltage power converter based on the hybrid series parallel resonant topology, PRC-LCC, with a capacitor as output filter are established. As a consequence of the selection of this topology, transformer ratio, and therefore secondary volume, is reduced. The mathematical analysis provides an original equivalent circuit for the steady-state and dynamical behavior of the topology. A new way to construct high-voltage transformers is also proposed, pointing out the advantages and establishing an original method to evaluate the stray components of the transformer before construction. The way to make compatible the characteristics of both, topology and transformer is illustrated in the frame of a practical application. To demonstrate the feasibility of this solution, a high-voltage, high-power prototype is assembled and tested with good performance and similar behavior to the one predicted by the models. Experimental results are shown on this particular.

Analytically calculating membrane displacement and the equivalent circuit model of a circular CMUT cell

Abstract: A small-signal equivalent circuit model and FEM often guide CMUT design The small-signal model is usually derived using a combination of numerical and FEM analysis A strictly analytical approach to CMUT design is desired because it provides design intuition and efficient numerical analysis In this paper, we show that the mass-spring-damper model used for many MEMS structures accurately captures the behavior of a CMUT with a circular plate We provide equations for the CMUT's equivalent mass-spring-damper parameters, pull-in point, and equivalent circuit parameters Comparison with FEM shows that the model accurately captures the CMUT's behavior for a wide range of designs Using this model, we can derive simple design equations, calculate the small-signal model for frequency response simulations, and simulate the CMUT's large-signal transient behavior

An Improved Small-Signal Parameter-Extraction Algorithm for GaN HEMT Devices

Abstract: A highly efficient and accurate extraction algorithm for the small-signal equivalent-circuit parameters of a GaN high electron-mobility transistor device is presented. Elements of the extrinsic equivalent-circuit topology are evaluated using a modified "cold field-effect transistor" approach whereby the undesirable need to forward bias the device's gate terminal is avoided. Intrinsic elements are determined based on a circuit topology, which identifies, for the first time, a time delay in the output conductance of GaN-based devices. The validity of the proposed algorithm has been thoroughly verified with excellent correlation between the measured and modeled S-parameters up to 50 GHz.

Charge dynamics in ionic polymer metal composites

Abstract: In this paper, we study the charge dynamics in ionic polymer metal composites (IPMCs) in response to a voltage difference applied across their electrodes. We use the Poisson–Nernst–Planck equations to model the time evolution of the electric potential and the concentration of mobile counterions. We present an analytical solution of the nonlinear initial-boundary value problem by using matched asymptotic expansions. We determine the charge and electric potential distributions as functions of time in the whole IPMC region. We show that in the bulk polymer region the IPMC is approximately electroneutral; in contrast, charge distribution boundary layers arise at the polymer-electrode interfaces. Prominent charge depletion and enrichment at the polymer-electrode interface are present even at moderately low input-voltage levels. We use the proposed analytical solution to derive a physics-based circuit model of IPMCs. The equivalent circuit comprises a linear resistor in series connection with a nonlinear capacitor. We derive closed-form expressions for the resistance and the capacitance by conducting a qualitative phase-plane analysis of the inner approximation of the asymptotic expansion. The circuit conductivity is independent of the IPMC dielectric constant and is proportional to the ion diffusivity; whereas, the capacitance is proportional to the square root of the dielectric constant and is independent of the diffusivity. The conductivity depends on the polymer thickness, while the capacitance is independent of it. The capacitance nonlinearity is extremely pronounced, and dramatic capacitance reduction is observed for moderately low voltage levels. We validate the proposed analytical solution along with the derived circuit model through extensive comparisons with finite element results available in the technical literature.

Transmission Line and Equivalent Circuit Models for Plasmonic Waveguide Components

Abstract: Modeling of waveguide junctions using transmission lines and lumped circuit elements is common practice in microwave networks. By the help of the scattering matrix formalism, it is possible to describe junction effects in a very concise way. Such a representation is crucial for the design of complex systems containing many interacting parts. Using scattering matrices, we characterize symmetric junctions between 2-D metal--insulator--metal (MIM) waveguides with optical signals at infrared frequencies (1550 nm) propagating in them. We verify our characterization by perfectly matching a wavelength-sized MIM waveguide to a subwavelength-sized one using a Smith chart. We then map the scattering matrix description to an equivalent lumped circuit representation and discuss the physical significance of its elements. We show that the simplified characteristic impedance model is appropriate for the deep subwavelength regime. The scattering matrix model for the MIM junctions leads to simplified analysis that can be integrated into circuit modeling software packages, such as SPICE.

A Coupled Thermal–Electromagnetic Analysis for a Rapid and Accurate Prediction of IM Performance

Abstract: The design of electrical machines for extreme operating conditions must include a thermal analysis coupled with the magnetic analysis. However, the traditional coupling of the thermal and the magnetic models can result in an unacceptable increase in computation time, particularly if finite elements (FEs) are used for the machine analysis. This paper proposes a coupled thermal-magnetic analysis of an induction motor (IM) with the primary goal of achieving a rapid and accurate prediction of the IM performance. Only a minimum set of FE magnetic analyses is carried out so as to determine the parameters of the IM equivalent circuit. These parameters are nonlinear and are adjusted on the basis of the operating point. Then, this equivalent circuit is coupled with a lumped-parameter thermal network to predict the temperature in each part of the IM. Since both the equivalent circuit and thermal network solutions are analytic, the analysis converges very rapidly. At the same time, the FE analysis yields a precise estimation of the IM parameters used in the equivalent circuit. Some experimental results are reported, showing the accurate prediction of the proposed methodology.

Fault Location for Underground Power Cable Using Distributed Parameter Approach

Abstract: This paper proposes an extensive fault location model for underground power cable in distribution system using voltage and current measurements at the sending-end. First, an equivalent circuit that models a faulted underground cable system is analyzed using distributed parameter approach. Then, the analysis of sequence networks in three-phase network is obtained by applying the boundary conditions. This analysis is used to calculate a fault distance in single section using voltage and current equations. The extension to multi-section is further analyzed based on Korean distribution systems. This method is an iterative process to determine a faulted section from the network. Finally, the case studies are evaluated with variations of fault distance and resistance, which also includes the evaluation of its robustness to load uncertainty.

Principle of Operation and Feature Investigation of a New Topology of Hybrid Excitation Synchronous Machine

Abstract: We present a new topology of hybrid excitation synchronous machine (HESM) and describe operational principles and features of the new configuration. Using the radial/axial distribution of the magnetic field, we develop an equivalent magnetic circuit model. We obtain magnetic flux, flux density, and induced voltage with various electrical magnetomotive forces by calculating the nonlinear magnetic circuit equation. We studied the Influence on the radial magnetic field of the axial magnetic field by 3-D finite-element method. The results are in good agreement with calculation by our magnetic circuit model. Our findings indicate that the air-gap flux density of a flux-concentrating HESM is high and the magnetic field in the air gap can be successfully regulated. Experimental results of 3 kVA prototype machine verify the feasibility of the structure and the correctness of our analysis.

Equivalent circuit method for static and dynamic analysis of magnetoelectric laminated composites

Abstract: Magnetoelectric equivalent circuit analytical method is presented for laminate composites of magneto-strictive Terfenol-D (TbxDy1−xFe2) and piezoelectric Pb(Zr1−xTix)O3 (PZT) operated in longitudinal magnetized and transverse polarized (or L-T), and transverse magnetized and transverse polarized (or T-T) modes. Magnetoelectric (ME) couplings both at low-frequency and resonance-frequency have been studied, and our analysis predicts that (i) the ME voltage coefficients of both L-T and T-T modes increase with increasing the thickness of the piezoelectric phase whereas magnetostrictive phase thickness keeps constant, and then tend to saturation when the thickness ratio of piezoelectric phase to magnetic phases is >3; (ii) there are the optimum thickness ratios that maximize magnetoelectric (ME) voltage coefficients for the two modes, which are dependent on elastic compliances ratio of piezoelectric phase and magnetostrictive phase; and (iii) the ME voltage coefficients are dramatically increased by a factor of ∼Qm, when operated at resonance frequency. A series of Terfenol-D/PZT laminates were fabricated, and the results were compared with the theoretical ones. Experiments confirmed that equivalent circuit method is a useful tool for optimum designs of ME laminates.

A New Resonant Gate-Drive Circuit With Efficient Energy Recovery and Low Conduction Loss

Abstract: In this paper, a new resonant gate-drive circuit is proposed to recover a portion of the power-MOSFET-gate energy that is typically dissipated in high-frequency converters. The proposed circuit consists of four control switches and a small resonant inductance. The current through the resonant inductance is discontinuous in order to minimize circulating-current conduction loss that is present in other methods. The proposed circuit also achieves quick turn-on and turn-off transition times to reduce switching and conduction losses in power MOSFETs. An analysis, a design procedure, and experimental results are presented for the proposed circuit. Experimental results demonstrate that the proposed driver can recover 51% of the gate energy at 5-V gate-drive voltage.

A new small-signal modeling and extraction method in AlGaN/GaN HEMTs

Abstract: In this paper, a new 20-element small-signal equivalent circuit for GaN HEMTs is proposed and correspondingly, a direct extraction method is developed. Compared with the 16-element conventional GaAs-based HEMT small-signal model (SSM), two parasitic distributed inter-electrode extrinsic capacitances and two additional feedback intrinsic resistances are considered. The new modeling approach for GaN HEMTs is verified by comparing the simulated small-signal S-parameter with the measured data over wide frequency and bias ranges.

Electrical Modeling of Thin-Film Transistors

Abstract: An overview of device physics-oriented electrical modeling of thin-film transistors (TFTs) is presented. Four specific models are considered: (i) square-law, (ii) 3-layer, (iii) comprehensive depletion-mode, and (iv) discrete trap. For each model, a functional assessment of model equations is undertaken in terms of independent and dependent variables, model parameters, physical operating parameters, and constraining inequalities in order to facilitate mapping of model equations into a corresponding equivalent circuit. Channel mobility and “subthreshold” current trends are elucidated. Finally, a conductance integral equation based on Shockley's gradual channel approximation is introduced and is employed in model development and device assessment.

Determination of NEMA Design Induction Motor Parameters From Manufacturer Data

Abstract: This paper proposes a simple method of determining the equivalent circuit parameters of National Electrical Manufacturers Association (NEMA) design A and B types of induction motors from standard manufacturer data such as rated output power, starting torque, breakdown torque, and efficiency and power factor at rated output power. A set of nonlinear equations for various quantities is first derived from the equivalent circuit with a single-cage rotor model, and then, equate to the corresponding actual values supplied by the manufacturer. These equations are then solved using a least-squares based algorithm to determine the motor parameters. The rotor parameters are considered as slip dependent to predict the starting torque of the motor and that requires refining the breakdown torque equation as well as the slip at which the breakdown torque occurs. The proposed method of determining the motor parameters is then tested on more than 300 large-size HV induction motors. The effectiveness of the proposed method is evaluated by calculating various external quantities of the motors through the estimated parameters and comparing them with the corresponding actual values supplied by the manufacturer.

Stochastic formulation of SPICE-type electronic circuit simulation with polynomial chaos

Abstract: A methodology for efficient tolerance analysis of electronic circuits based on nonsampling stochastic simulation of transients is formulated, implemented, and validated We model the stochastic behavior of all quantities that are subject to tolerance spectrally with polynomial chaos A library of stochastic models of linear and nonlinear circuit elements is created In analogy to the deterministic implementation of the SPICE electronic circuit simulator, the overall stochastic circuit model is obtained using nodal analysis In the proposed case studies, we analyze the influence of device tolerance on the response of a lowpass filter, the impact of temperature variability on the output of an amplifier, and the effect of changes of the load of a diode bridge on the probability density function of the output voltage The case studies demonstrate that the novel methodology is computationally faster than the Monte Carlo method and more accurate and flexible than the root-sum-square method This makes the stochastic circuit simulator, referred to as PolySPICE, a compelling candidate for the tolerance study of reliability-critical electronic circuits

Model-based electrochemical estimation of lithium-ion batteries

Abstract: A linear Kalman filter based on a reduced order electrochemical model is designed to estimate internal battery potentials, concentration gradients, and state of charge (SOC) from external current and voltage measurements. The estimates are compared with results from an experimentally validated one-dimensional nonlinear finite volume model of a 6 Ah hybrid electric vehicle battery. The linear filter gives, to within ~2%, performance in the 30%-70% SOC range, except in the case of severe current pulses that draw electrode surface concentrations to near saturation and depletion; however, the estimates recover as concentration gradients relax. With 4 to 7 states, the filter has low order comparable to empirical equivalent circuit models but provides estimates of the batterypsilas internal electrochemical state.

Analysis of CLL Voltage-Output ResonantConverters Using Describing Functions

Abstract: A new AC equivalent circuit for the CLL voltage-output resonant converter is presented, that offers improved accuracy compared with traditional FMA-based techniques. By employing describing function techniques, the nonlinear interaction of the parallel inductor, rectifier and load is replaced by a complex impedance, thereby facilitating the use of AC equivalent circuit analysis methodologies. Moreover, both continuous and discontinuous rectifier-current operating conditions are addressed. A generic normalized analysis of the converter is also presented. To further aid the designer, error maps are used to demonstrate the boundaries for providing accurate behavioral predictions. A comparison of theoretical results with those from simulation studies and experimental measurements from a prototype converter, are also included as a means of clarifying the benefits of the proposed techniques.

A New Class of Dual-Mode Dual-Band Waveguide Filters

Abstract: This paper presents a new class of dual-mode dual-band filters in which each polarization is dedicated to a selected band. The equivalent circuit is a parallel combination of two inline networks that represent each polarization. A transmission zero is generated between the two bands by properly adjusting the relative orientations of the input and output coupling apertures. For filters where each branch contains an odd number of resonators, the input and output apertures have the same orientations. For filters where the order of each branch is even, the two apertures are orthogonal to each other. Filters using three and four dual-mode cavities are designed and presented. Different arrangements of the dual-mode cavities are also presented.

Electrical modeling of Piezoelectric ceramics for analysis and evaluation of sensory systems

Abstract: Piezoelectricity is an ability of some materials to generate an electric potential in response to applied mechanical stress. Piezoelectric ceramics are often used for sensory systems to monitor mechanical characteristics of structures through an electrical signal. Thus, to support system level analysis and evaluation of sensory systems, understanding and estimating the electrical behavior of piezoelectric ceramics with a minimum effort is valuable. This paper proposes an equivalent circuit model for piezoelectric ceramics, with a PZT patch as the specimen. The proposed model approximates the electrical behavior of piezoelectric ceramics with up to 100% accuracy for unloaded and 93% accuracy for loaded PZT, and provides a modeling procedure that can easily be automated.

Induction Motor Equivalent Circuit Including the Stray Load Losses in the Machine Power Balance

Abstract: In this paper, the stray load losses due to the air gap spatial harmonics effects on the rotor squirrel cage are considered and a simplified induction motor equivalent circuit able to include them in the machine power balance is reported. In the proposed model, an additional resistance appears in series with the stator impedance. This additional parameter has been defined on the basis of power balance considerations applied to the induction motor classical theory. The complete theoretical analysis together with the guidelines to measure the equivalent circuit parameters are reported in detail. Finally, the proposed approach has been experimentally verified using five total enclosed fan cooled induction motors.

Capabilities of finite element analysis and magnetic equivalent circuits for electrical machine analysis and design

Abstract: This paper reviews the literature concerned with capabilities and limitations of finite element analysis (FEA) and magnetic equivalent circuit (MEC) analysis for electrical machine design. The most common known models are based on equivalent circuits and related analytical models, or on FEA. Analytical models use highly simplified magnetics, and have difficulty extending into saturation. FEA typically uses magnetic vector potential representations that model additional effects such as eddy currents, but requires detailed nonlinear models for saturation and hysteresis. MEC methods represent a third possibility for electrical machine analysis, based on permeance network models comprising reluctances and mmf sources. Advantages of the MEC method include reduced model complexity compared to FEA, enhanced accuracy compared to analytical approaches, ease of parameterization, methods for extension to 3-D capability, and fast computation time. One of the most significant concerns related to literature in this area is that very few papers report thorough comparisons between experimental measurements and simulation tools for electromechanical devices. Among those that do, even fewer compare electromechanical forces and torques. With less than 15 exceptions, the few papers providing such comparisons report ldquogood agreement, rdquo but in fact show errors of 10% or more between tests and simulations. Many papers with experimental results do not compare torque or force results or present error analysis. This is most unfortunate, as many authors deen to consider FEA results ldquodefinitiverdquo and use them as a basis for model comparisons. Saturation and iron losses appear to be the likely culprits. In a few papers, the reported analysis method takes full nonlinear magnetic effects into account. When magnetic saturation, eddy currents, hysteresis losses, and similar effects are modeled with care and in detail, differences between simulations and experiments typically are on the order of 5%.

Improved circuit model for left-handed lines loaded with split ring resonators

Abstract: In this letter, an improved lumped element equivalent circuit model for left-handed lines based on split ring resonators (SRRs) is presented and discussed. It is rigorously demonstrated that although the previously accepted circuit model of these metamaterial transmission lines (a π circuit) provides a good description of device behavior, its electrical parameters do not actually describe the physics of the structure. Conversely, the parameters of the improved equivalent circuit model are representative of the different elements of the structure, including the SRRs, the shunt inductive elements and the host line. It is also shown that the proposed model can be transformed to a π model which is formally identical to the previous reported model of SRR-based left-handed lines. With this transformation, the main relevant characteristics of these left-handed lines are perfectly interpreted.

High-power piezoelectric acoustic-electric power feedthru for metal walls

Abstract: Piezoelectric acoustic-electric power feed-through devices transfer electric power wirelessly through a solid wall using elastic waves. This approach allows for the elimination of the need for holes through structures for cabling or electrical feed-thrus . The te chnology supplies power to electric equipment inside sealed containers, vacuum or pressure vessels, etc where holes in the wall are prohibitive or may result in significant performance degradation or requires complex designs. In the our previous work, 100-W of elec tric power was transferred thr ough a metal wall by a small, piezoelectric device with a simple-structure. To meet requirements of higher power applications, the feasibility to transfer kilowatts level power was inve stigated. Pre-stressed longitudinal piezoelectric feed-thru devi ces were analyzed by finite element modeling. An equivalent circuit model wa s developed to predict the char acteristics of power transfer to different electric loads. Based on the analytical results, a prototype device was designed , fabricated and successfully demonstrated to transfer electric power at a level of 1-kW. Methods of minimizing plate wave excitation on the wall were also analyzed. Both model analysis and experime ntal results are presented in detail in this paper. KEYWORD : piezoelectric devices, acoustic wave, electric powe r supply, wireless power feed, pressure vessels.

On-Chip Power-Grid Simulation Using Latency Insertion Method

Abstract: Ensuring the integrity of the power supply in the power distribution networks (PDNs) of a chip is essential for building reliable high-performance chips. To ensure the power integrity, accurate, and memory- and time-efficient simulation approaches for simulating the power-supply noise in the on-chip PDN are essential. In this paper, a finite-difference formulation based on the latency insertion method (LIM) has been employed for simulating the power-supply noise in the on-chip PDN. A new common-mode type equivalent circuit has been proposed. In this equivalent circuit, a capacitance to ideal ground may not be present at all the nodes. Further, the nodes can be capacitively coupled to each other. To avoid inverting a large nonbanded matrix, a small capacitance to ground is added to a node that did not have any capacitance to ground, and a small series inductance is added to any floating capacitor that did not have any series inductance. Approximate closed-form expressions to compute the values of these capacitances to ground and series inductances have been proposed. The accuracy of the LIM-enabled transient simulation and the accuracy of the proposed closed-form expressions have been demonstrated. The memory and time complexity of the simulation for each time step have been shown to be O(Nn) each, where Nn is the number of nodes in the equivalent circuit. Stability condition is derived for the first time for multidimensional inhomogeneous RLC circuit. A upper bound of the time step is derived from the stability condition. Using this bound on the time step, the runtime of the overall transient simulation has been estimated to be approximately proportional to Nn 2-2.5 for Nn in the order of millions.

An Efficient and Reliable Shielding Effectiveness Evaluation of a Rectangular Enclosure With Numerous Apertures

Abstract: An efficient analytical and accurate model to predict the shielding effectiveness of a rectangular enclosure with numerous small apertures is presented. In this paper, an appropriate equivalent admittance for the perforated side is suggested amid the free space and the enclosure, utilizing the traditional waveguide circuit model where the enclosure is represented by a short-circuited rectangular waveguide. The simulation results of this model are in better agreement with measurements than that of the original waveguide equivalent circuit model. This method is applicable to an array of square and circular holes of staggered and square configurations.