AC Voltage Source Research Articles

Analysis of the Effect of DAC Resolution on AC Voltage Generated by Digitally Synthesized Source

This paper presents an analysis of the effect of the digital-to-analog converter resolution on the root-mean-square value of the sinusoidal signal generated by the digitally synthesized source (DSS) of low-frequency standard ac voltage. The analysis applies to the DSS being calibrated using the peak-to-peak method.

Stabilising current driver for high‐voltage light‐emitting diodes

High-voltage light-emitting diodes (HV LEDs) possess higher cut-in voltages and works at a high supply voltage. As the specific feature, they can be directly driven via universal utility-line voltages after appropriate rectification. This significantly simplifies the circuit structure and reduces the manufacturing cost. While HV LEDs are driven directly by half-wave rectified DC power source, which is an impure form of DC, their lumen is easily affected by changing the AC voltage source, while only constant current control is insufficient for stable lumen, thus hindering their usefulness in practical applications. This study proposes a simple, however effective, HV LED driver via a proportional and integral current control accompanied with feedforward compensation which is capable of maintaining stable lumen under changing AC voltage sources. Experimental results have demonstrated satisfactory performance in lighting.

Geometric dependence in the electric response of electro-ionic polymer devices

Asymmetric and symmetric two-terminal PEDOT:PSS-electrolytic devices were fabricated and their electric response (current–voltage curve) was measured using an applied AC voltage source. The current–voltage curve for the symmetric devices was similar to a Bipolar Sigmoid function. By introducing asymmetry into the devices the current–voltage curve could be altered to resemble a linear ramp function. This work shows that the shape of the electrical response of these polymer devices can be used to implement activation transfer functions for artificial neurons, which are used to implement artificial neural networks.

Frequency Splitting Analysis of Two-Coil Resonant Wireless Power Transfer

Frequency splitting has been widely observed in resonant wireless power transfer (RWPT). However, there are some misunderstandings concerning this phenomenon in the two-coil RWPT structure. Based on the circuit theory, this letter deduces the expressions of the voltage ratio, the output power, and the efficiency varying with the driving frequency, supplied by a constant ac voltage source. Frequency splitting occurs in the voltage gain and the output power, and the splitting frequency points are deduced. As to the efficiency, no frequency splitting exists, contrary to the current mainstream research. The calculations and the experiments confirm these conclusions.

Electromechanical Modeling of a Contactor with AC Coil

Two ways of modeling a contactor with an AC coil are shown in this article. Both models are based on the explicit definition of the inductances by lumped parameters, and the difference between them is the considering or not of the effect of the shading rings. The equations were formulated to obtain the contact operation time and to describe the contactor coil current when the coil is fed with different values of the AC source voltage. The comparison between theoretical and experimental results shows that the models are satisfactory in both cases. This demonstrates the possibility of obtaining accuracy without considering the shading rings. The main advantage of the inclusion of the effect of the shading rings is the obtaining of a qualitative description for the currents in the shaded rings.

Identifying Generators at Risk of SSR in Meshed Compensated AC/DC Power Networks

The paper presents a methodology to identify generators at risk of subsynchronous resonance (SSR) in meshed AC/DC networks. Two risk indices are developed to rank generators based on the level of exposure to SSR. One of them measures the severity of subsynchronous torsional interactions, and the other indicates the gravity of transient torque problem. It is shown that proposed indices can be used to identify generators in the network that are at the risk of experiencing high mechanical torques due to SSR and to rank them based on severity of potential exposure to SSR. The methodology is demonstrated on meshed 16-machine, 68-bus IEEE test network with different series compensation levels of AC lines, asymmetrical compensation and voltage source converter (VSC) based HVDC lines. Finally, electromagnetic transient simulations are used to verify the ranking of generators obtained using developed indices.

Inception of transients and transient suppression methods

This tutorial paper offers a fresh perspective on the analysis of transient phenomena. The subject, that pervades all areas of electrical engineering, is of special importance in power and energy systems where voltages and currents can have very large magnitudes and where transient events can cause power quality problems. Two main aspects are addressed in the paper: the inception of transients and transient suppression methods. The analysis of transient inception requires the consideration of short time scales where capacitive and inductive distributed effects must be accounted. The analysis of transient suppression methods, applied to an LR-circuit driven by DC or AC voltage sources, is illustrated with a two-switch technique where long time scales are appropriate. Copyright © 2013 John Wiley & Sons, Ltd.

Rectifier Capacitor Filter Stress Analysis When Subject to Regular Voltage Fluctuations

Lamp flicker levels that arise as a result of voltage fluctuations can exceed limits set by appropriate standards. New lamp types such as compact fluorescent lights are less sensitive to voltage fluctuations as their flicker characteristics are considerably different compared to those of the traditional incandescent lamp. These differences could support the moderation of the present voltage fluctuation and flicker standards and hence the associated limits. The potential detrimental effects on electrical equipment which may be caused by relaxation of these limits should be investigated before any changes to the present standards take place. The impact of voltage fluctuations on a full-bridge rectifier with a capacitor filter is considered as a case study in this paper. Such a circuit is found at the front end of many different types of equipment that are connected to the public ac supply network. The capacitor ripple current characteristic is of particular interest. The research reported in this paper indicates that the filter capacitor will accumulate and dissipate increased amount of charge when the rectifier is subjected to ac source voltage fluctuations. The consequence is that the RMS value of the capacitor current will increase, where the magnitude of this increase is related to the modulation frequency and magnitude of the fluctuating voltage. Therefore, an ac supply with a voltage fluctuation component will cause a full-bridge rectifier with capacitor filter to sustain increased stress. This stress may accelerate the capacitor ageing process, eventually resulting in premature equipment failure. The research indicates that there is a need for indices other that the short-term and long-term flicker indices required for equipment compatibility levels.

Estimation of electron temperature in atmospheric pressure dielectric barrier discharge using line intensity ratio method

Dielectric Barrier Discharge was produced by applying high voltage AC source of frequency (10-30 KHz) and potential difference of (0-20) kV across two parallel plate electrodes with glass as dielectric barrier. Optical emission spectroscopy was used for the characterization of the discharge produced at atmospheric pressure. The emission spectra in the range of 200 nm to 850 nm have been analyzed to estimate the electron temperature by line intensity ratio method. The results showed that the electron temperature is about 0.9 eV. Kathmandu University Journal of Science, Engineering and Technology Vol. 8, No. II, December, 2012, 37-42 DOI: http://dx.doi.org/10.3126/kuset.v8i2.7323

ブリッジ結合磁路を用いた磁気発振型DC-AC変換器の数値解析

This paper describes the numerical circuit analysis of a magnetic oscillation direct current/alternating current (dc-ac) power converter using a magnetic control device called a bridge-connected magnetic circuit. The converter can supply electric power to an ac-voltage source such as a line electric power source and can control the output electric power by using the small dc-current that flows through the control winding of the bridge-connected magnetic circuit. A simulation model of the bridge-connected magnetic circuit and a simulation circuit of the dc-ac converter based on a general purpose circuit simulation program called “SPICE” are proposed for the quantitative analysis of the dc-ac converter. The fundamental characteristics of the dc-ac converter were calculated using SPICE. Comparisons between the simulation results and the experimental ones are presented in this paper.

Reversibility of electric-field-induced mechanical changes in soft tissues [Letters

Recently, ultrasound has been used to study the physiological-level electric-field-induced mechanical changes (EIMC) in general soft biological tissues. Here, we present the experimental results on the dependence of EIMC on the polarity of the applied electric field. We applied an ac voltage source to heart tissues and monitored the amplitude changes and time shifting of the ultrasound echoes. The shifting of the echoes was decomposed into a trend component and a fluctuation (feature) component. The changes in amplitude and the fluctuation component of the time shift, but not the trend component of the time shift, can be mostly reversed by reversing the polarity of the applied voltage. The polarity-dependence study reveals two different mechanisms underlying EIMC.

Using gauss - Jordan elimination method with CUDA for linear circuit equation systems

Many scientific and engineering problems can use a system of linear equations. In this study, solution of Linear Circuit Equation System (LCES) for an nxn matrix using Compute Unified Device Architecture (CUDA) is described. Solution of LCES is realized on Graphics Processing Unit (GPU) instead of Central Processing Unit (CPU). CUDA is a parallel computing architecture developed by NVIDIA. Linear Circuits include resistance, impedance, capacitance, dependent - independent current sources and DC, AC voltage source. In this study, solutions of circuits that include resistance, independent current sources and DC voltage source have analyzes. Circuit analysis frequently involves solution of linear simultaneous equations that are solved Gauss-Jordan Elimination Method in this study. Gauss-Jordan Elimination is a variant of Gaussian Elimination that a method of solving a linear system equations (Ax=B). Gauss-Jordan Elimination is an algorithm for getting matrices in reduced row echelon form using elementary row operations. Gaussian Elimination has two parts. The first part (Forward Elimination) reduces a given system to triangular form. The second step uses back substitution to find the solution of the triangular echelon form system Because of elements of unknowns column matrix are dependent on each other, second step algorithm is not appropriate for parallel programming. Two parts of Gauss–Jordan Elimination are not like Gaussian Elimination's part so it is preferred. GPU implementation is more faster than solution of linear equation systems on CPU

Plasma Production by Multiphase Alternating-Current Underwater Discharge

The multiphase alternating-current (ac) voltage source ensures the formation of plasma in water by providing an efficient breakdown voltage for the electrodes connected in parallel. The voltage-driving source was composed of 3-phase transformers to supply 12-phase ac voltage and a voltage regulator to control the output voltage of the transformers. The arrangement provided the stable large-scale underwater plasma by giving the capillary electrodes in water independent powers without voltage drop due to phase difference made from the voltage source. This plasma system in a flowing water would be useful as a continuous massive water treatment for the purification, sterilization, or disinfection of objects or materials.

A Design Methodology for Smart LED Lighting Systems Powered By Weakly Regulated Renewable Power Grids

The increasing use of intermittent renewable energy sources to decarbonize electric power generation is expected to introduce dynamic instability to the mains. This situation is of particular concern for mini-grids or isolated grids in which wind and/or solar power sources are the dominant or the sole power sources. In this paper, we utilize the photo-electro-thermal theory to develop a design methodology for LED lighting systems for weakly regulated voltage sources, with the objectives of minimizing the fluctuation of the human luminous perception and adopting reliable LED driver with long lifetime and robustness against extreme weather conditions. The proposed LED system, practically verified in a 10 kVA small power grid driven by an ac voltage source and a wind energy simulator, can be considered as a smart load with its load demand following the power generation. A typical swing of 40 V in the mains will cause only 15% actual light variation in a 132 W LED system when compared with 40% change in 150 W high-pressure-sodium lamp system. The design methodology enables future large-scale LED systems to be designed as a new generation of smart loads that can adapt to the voltage and power fluctuations arising from the intermittent nature of renewable energy sources.

Development of rapid oral bacteria detection apparatus based on dielectrophoretic impedance measurement method

In this study, a bacteria detection apparatus based on dielectrophoretic impedance measurement (DEPIM) method was demonstrated for rapid evaluation of oral hygiene. The authors integrated a micro electrode chip on which bacteria were captured by dielectrophoresis (DEP), an AC voltage source to induce DEP force, and an impedance measurement circuit to a portable instrument that enables rapid and automated oral bacterial inspection in hospitals and clinics. Special considerations have been made on effects of high electrical conductivity of oral samples on DEP force and DEPIM results. It was shown experimentally and theoretically that using a higher electric field frequency for the DEP bacteria trap and the impedance measurement could realise DEPIM application to bacteria inspection from oral samples with higher conductivity. Based on these investigations, the authors optimised the frequency condition of the DEPIM suitable for inspecting an oral sample along with the design and development of a portable DEPIM apparatus for on-site inspection of oral bacteria. Under the optimised frequency condition, DEPIM results were in good agreement with the conventional culture method showing significant applicability of the DEPIM apparatus for practical rapid oral bacteria inspection.

CuBr blue light emitting electroluminescent thin film devices

AbstractVisible blue cathodoluminescence (CL), photoluminescence (PL), x‐ray excited optical luminescence (XEOL) and electroluminescence (EL) via Zf free excitonic emission have been obtained from CuBr thin films deposited on glass, Cr coated glass, GaAs and Si substrates. In addition to the Zf emission several peaks corresponding to Cu+ emissions via 3d94s ↔ d10 transitions were observed on the AC EL spectrum at 2.10, 2.7, 3.03, 3.07 and 3.80 eV. X‐ray diffraction (XRD) measurements confirmed that the vacuum evaporated CuBr thin films grow preferentially with a (111) orientation irrespective of the substrate. While the AC voltage source was found to have no detrimental effects on CuBr thin films, cathodic deposition of Cu metal via electrolytic decomposition was observed under steady state DC voltage stresses. The results from the various luminescence experiments suggest that CuBr thin films may be used as a phosphor layer in blue emitting AC thin film electroluminescent devices (ACTFELD) (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Improved Characteristics to Control Output Electric Power of Magnetic Oscillation DC-AC Power Converter

This paper describes the fundamental characteristics of a new magnetic oscillation direct current/alternating current (dc-ac) power converter that had fast recovery diodes added to it. The converter is constructed with a non-linear magnetic core and power MOSFETs. An ac-voltage source such as that for line electric power is connected in series to an excitation winding of the magnetic circuit. The converter can supply electric power to the ac-voltage source, and its output electric power can be controlled with a small signal current that flows through the control winding. The waveform for the output current of the converter is almost sinusoidal. The output electric power of the converter was increased by adding the fast recovery diodes outside the MOSFETs to cancel and replace the body-diodes of the MOSFETs.

A Series-Tuned Inductive-Power-Transfer Pickup With a Controllable AC-Voltage Output

This paper presents a new type of series ac-processing pickup used in inductive-power-transfer applications. The proposed pickup uses an ac switch operating under zero-current-switching conditions in series with a resonant network to produce a controllable ac voltage source suitable for driving incandescent lights. When a rectifier is cascaded onto this pickup, it can also produce a precisely controlled dc voltage. This topology eliminates the need to use an extra buck converter after the traditional series pickup for controlling the output load voltage to a desired value, which may be different from the induced voltage of the pickup. Furthermore, this pickup has the ability to control the inductor current directly, and hence, eliminate the transient inrush current at startup for the series-tuned resonant tank. The circuit is analytically analyzed and the maximum efficiency for a 1.2-kW prototype is measured to be 93%.

Numerical Analysis of Fundamental Characteristics of Magnetic Oscillation DC-AC Power Converter

This paper describes the numerical analysis of fundamental characteristics of a magnetic oscillation direct current/alternating current (dc-ac) power converter that can supply electric power to an ac-voltage source such as a line electric power source. We present a simulation model of the magnetic oscillation circuit based on a general purpose circuit simulation program called “SPICE” to quantitatively analyze it. The simulation results of the fundamental characteristics agree well with those from experiments. A method of improving the characteristics to control the output electric power, which is based on the analytical results, is also described in this paper.

Pulsewidth Modulation Method of Matrix Converter for Reducing Output Current Ripple

A matrix converter interfaces with three-phase ac voltage source, which creates three different virtual dc-link voltages. In this paper, a new pulsewidth modulation (PWM) method for the matrix converter is proposed to generally use these three virtual dc-link voltages. By using the two higher line-to-line voltages as the virtual dc-link voltages, the proposed method can create the identical switching sequences to those created by the conventional space vector PWM (SVPWM) method. Moreover, the proposed method is able to select the appropriate virtual dc-link voltage, according to the PWM purpose and/or load condition. In this paper, the virtual dc-link voltages adjacent to the output voltage reference are introduced to reduce output-current switching ripples. The feasibility of the proposed PWM method was verified by a computer simulation and experimental results. The output voltage and current waveforms produced by using the proposed method can be equal or better than those created using the conventional SVPWM method. Moreover, a new switching sequence that reduces output-current switching ripple can be easily adopted within the proposed PWM method. The harmonic characteristics of output current created using the proposed method are markedly improved over those using the conventional PWM method.