High Frequency AC Voltage Research Articles

Interferometric characterization of high-frequency piezoelectric effects in hydroxyapatite thin films

Hydroxyapatite (HAp) qualities such as biocompatibility and piezoelectricity make it an excellent material for biomedical applications. Here, HAp thin film samples were fabricated onto silica substrates to study their piezoelectric behavior with optical interference. Thin solid films were deposited using previously synthesized HAp powder, sol-gel, and spin-coating techniques. The samples were characterized by scanning electron microscopy, energy dispersive X-ray, Raman, and UV-Vis spectroscopies. The statical piezoelectric effect of the samples was studied by using a finite element method and computational software. Additionally, an experimental Bode analysis allows computing the internal electrical components of the films using high-frequency AC voltage. The electrical behavior is related to the equivalent circuit of a piezoelectric crystal, which indicates the range of frequencies where the electromechanical effect is maximum. A Sagnac interferometer was used to characterize the strain in the HAp as a function of the electrical input frequency. The displacement of the interferometric fringe pattern allows us to estimate the change in the thickness of the sample and compute the piezoelectric constant. The synthesis of HAp thin films with piezoelectric properties provides an effective way to produce sensors and actuators for technological applications.

Solar Induction Cooker

There is no available power grid in the rural areas in many countries in South America, Asia and Africa. st places, Fossil fuel or wood is used for cooking. Besides environmental issues, fossil fuel and wood from trees are being depleted at a fast rate. Solar power is available everywhere during day time in all countries. This solar induction cooker uses a solar panel, which gives a variable dc, to charge a battery. The dc from the battery is converted to a high frequency ac voltage by an inverter circuit. This inverter circuit supplies alternating current to a coil on a magnetic core where alternating flux is produced. This alternating flux produces in the magnetic core Eddy current and Hysteresis ‘losses’ inside the magnetic core. In this application, these losses will produce useful heat. A cooking pot placed on the magnetic core will be used for cooking.

Dynamic measurement of magnetic characteristics of switched reluctance motor

Introduction. Switched reluctance motor (SRM) is a type of electric motor featuring nonlinear magnetic characteristics. The flux linkage or inductance profile of SRM is usually required for the purpose of high control performance, and can be normally obtained through conventional static test by using DC or AC method when the rotor is locked. Problem. However, it is not practical to use the conventional method of measurement when the specific apparatus for locking the rotor is unavailable. Besides, due to the magnetic nonlinearity of SRM, the saturation effect makes it difficult to obtain the saturated magnetic characteristics, and the conventional static AC test fails to address this problem. Novelty. In this paper, a dynamic measurement method of the magnetization curves of SRM is proposed which allows the measurement take place while the motor is running with load. Methodology. Based on the conventional static AC test, the proposed measurement handles the saturation problem successfully by introducing a DC offset in the high frequency AC voltage. Phase inductance with different rotor positions and currents can be obtained by analyzing simple equivalent circuit. Practical value. Simulation is conducted in MATLAB/Simulink environment and the results have verified that the proposed dynamic measurement can effectively obtain the magnetic characteristics of SRM.

Computational study on the discharge dynamics of atmospheric pressure He plasma driven by high frequency AC voltage

A two dimensional self-consistent fluid model has been established to investigate the discharge dynamics of double-ring electrode He atmospheric pressure plasma jet (APPJ) driven by high frequency AC voltage. The difference of the internal stream and external jet and the influence of the change of applied voltage polarity on plasma discharge characteristics has been discussed. It has been discovered that the capacitive breakdown characteristic of the double ring electrode significantly enhances the intensity of the APPJ. The discharge intensity of the external jet is stronger than that of the internal stream and the propagation speed of the external jet is faster than that of the internal stream due to the ionization and Penning ionization of N2 and O2. Therefore, the density of reactive species in the external jet is greater than that in the internal stream. When the negative voltage is applied to the downstream electrode, the propagation direction of the internal stream changes to the downstream electrode. The ionization of the external jet is also concentrated near the downstream electrode and in the streamer head. The radial propagation distance of the external jet on the dielectric surface continues to increase and the peak value of the radial electric field is concentrated at the streamer head. When the applied voltage changes from negative to positive, the propagation direction of the internal stream turns to the upstream electrode and the upstream jet is formed above the electrode. At the beginning of the positive cycle, the radial propagation distance of the external jet is shortened due to the effects of the electron attachment of O2 and the radial electric field. With the increase of applied voltage, the ionization in the streamer head gradually increases, which promoted the radial propagation of external jet.

Understanding the Surface Condition of Silicone Rubber Nanocomposite Due to Corona Aging Using AFM Imaging and LIBS Spectroscopy

Silicone rubber insulators undergo degradation when they are exposed to corona discharges. The present study explores the surface degradation behavior of silicone rubber alumina nanocomposites due to corona aging using high-frequency ac voltage. The electric field distribution on the sample surface during corona aging is simulated using COMSOL. The change in silicone rubber functional group is studied using Fourier transform infrared (FTIR) spectroscopy analysis. The influence of corona aging time on the surface roughness recovery of silicone rubber nano alumina composites is studied using an atomic force microscopy (AFM). The elemental distribution behavior and change in the emission spectra persistence time are analyzed during recovery period of corona-aged silicone rubber nanocomposites using laser-induced breakdown spectroscopy (LIBS) technique. The addition of alumina nanofiller to the silicone rubber improves the resistance to aging due to corona discharge. Loss and recovery of hydrophobic property of silicone rubber due to corona aging were determined using static contact angle measurement. The results show a direct correlation between the contact angle and the surface roughness recovery characteristics. They indicate that the nanocomposite having a 5 wt% alumina content exhibits the highest resistance to corona discharge with least surface damage. Furthermore, fast recovery was observed in the first few hours after corona aging, and most samples eventually regained their properties after about 8 h of recovery time.

Power Quality Control System of High-Power-Density Switching Power Supply for Green Environment

There is higher harmonics and electromagnetic interference caused by high-power-density switching power supply during high-frequency and normal operations which affects power quality of switching power supply and also impacts the environment. To solve this problem, this paper proposes a dual digital signal processor (DSP) controller suitable for unified power quality regulators and designs high-power-density switching power supply control system for promoting green environment. The overall structure of the system is divided into two parts, the power main circuit and the control circuit. In the main power circuit, the electromagnetic interference (EMI) filter is used to filter the input AC voltage and convert it into a stable DC voltage. A high-frequency inverter is used to invert the DC voltage into a high-frequency AC voltage to achieve harmonic control and reactive power compensation. In the control circuit, dual DSP controller is used to improve real-time detection, control of the output voltage, and current and driver temperature of the high-power-density switching power supply, while high-precision analysis and processing system collect different information and then achieve the power quality control of the switching power supply based on system software to keep this environment green. The experimental results suggest that the harmonic content of the experimental objects controlled by the system is reduced by 16.7% compared with the existing power quality control and the absolute error of the system is less than 0.02 V which improves the de-noising performance. The power generation systems require that the consumption of natural resources and renewable energy solutions can assist in saving the natural resources.

Standalone Clamping Switched Capacitor-Based Modular DC Transformer for MVdc Application

This article introduces a standalone clamping switched capacitor-based dc transformer (CSCDCT) for the medium-voltage dc power grid. The CSCDCT owns the functions of the dc fault isolation and the online redundant design, and hence, the power distribution reliability can be guaranteed. It is also shown that the additional advantages of the CSCDCT are the matching regulation of the high-frequency ac voltages and the voltage self-balance of the dc capacitors. The coupling effect of ac voltage amplitudes and dc voltages can be eliminated by the matching regulation, and the action of dc voltages will not alter the amplitude of high-frequency ac voltages in CSCDCT, improving the soft-switching performance, efficiency, and control stability of the DCT system. Besides, by the self-balance capability, the dc capacitor voltage balancing mechanism is not required for the individual unit although two capacitors are used in each submodule. This simplifies the control system of the CSCDCT. The topology, operating mode, voltage matching modulation, current characteristic, switching performance, and power loss of the CSCDCT are investigated in detail. The correctness of the analysis is validated through the experimental and simulation results.

Effect of Magnetic Field on Partial Discharge Initiated by Metallic Particle in Thermally Aged Natural Esters Under AC and Harmonic Voltages

This paper reports the experimental and theoretical investigations of particle levitation voltage on thermally aged ester fluid, under AC and harmonic AC voltages, in the presence of both electric and magnetic fields (130 mT and 160 mT). The results indicate a higher sensitivity to identify partial discharge (PD) initiated due to particle movement in aged ester fluids with an ultra-high frequency (UHF) sensor than the fluorescent fiber technique. The cause for the reduction in sensitivity of PD detection due to the fluorescent fiber technique with thermally aged fluid is analyzed using steady-state fluorescent measurement. The reduction in the levitation voltage noticed under high-frequency AC voltages is much more severe than its impact under the fundamental frequency of AC supply voltage. In addition, the presence of a magnetic field reduces the magnitude of levitation voltage substantially. The UHF signals generated due to particle movement-initiated discharges with aged ester fluids indicate a shift in its dominant frequency of 0.9 GHz under the absence of a magnetic field to around 0.6 GHz with the effect of a magnetic field.

A Multilevel Inverter for Contactless Power Transfer System

In contactless power transfer (CPT) system, voltage-source inverters are widely used with a resonant tank. However, because of the influence of the working environment, aging, and other factors, the resonant frequency of the primary varies. Moreover, the reflected equivalent impedance of the secondary coil may affect the design of a resonant tank with a constant switching frequency. In this brief, a multilevel inverter (MLI) without the resonant circuit tuning is proposed for the CPT system. The proposed inverter can produce a high-frequency ac voltage with an approximated sinusoidal envelope for the primary coil. According to the equation developed for the inverter, low-order harmonics can be eliminated by selecting an appropriate input voltage ratio and switching angles for the switches. Furthermore, the cancelation of multiple harmonics can be achieved by designing multilevel circuits. The advantages of the proposed MLI include the reduction in low-order harmonics, low voltage stress, and high reliability. Hardware experimental results were obtained for a CPT system prototype to verify the performance of the proposed MLI.

Analisis Pengaturan Parameter Sinusoidal Pulse Width Modulation pada High Precission Closed Loop Full Bridge Bipolar Inverter untuk Pembangkit Tegangan Tinggi Berfrekuensi Tinggi

The application of high voltage becomes more important and wider. High voltage is needed in the process of reducing air contaminants, waste treatment, sanitation, disinfecting microorganisms, testing for insulating high voltage equipment, and transmitting electrical energy. The problem of high voltage AC generation system is still in a large scale, static, not portable, and very expensive. This paper presents an analytical design of a high-voltage AC high-frequency based on power electronic. It is portable, less expensive, and eaasier to control the amplitudo and frequency. The application of the Full Bridge Bipolar Inverter topology with the Sinusoidal Pulse Width Modulation switching method provides variable sinusoidal AC voltage outputs (Vo) on its amplitude and frequency. The Tesla Coil Transformer amplifies the amplitude in accordance with the classification of the high voltage AC in the order of Kilo Volt. The Closed Loop control system in the Bipolar Inverter Full Bridge topology provides high accuracy results between the given setting values and the actual amplitude output and the expected high-frequency AC voltage. Analysis of the SPWM switching pattern parameter settings shows stability for several loading variations

Microscopic analysis of polyimide nanocomposites aging mechanism exposed to partial discharges under high frequency voltage stress

For the sake of investigating the influence of nanoparticles on the reduction in structural damage of neat polyimide (PI) and PI nanocomposites, scanning electron microscope (SEM) based microscopic study was conducted on unaged and aged pure PI and PI/TiO2 nanocomposite samples exposed to partial discharge activity under high frequency ac voltage stress. PI/TiO2 nanocomposites with 2, 3 and 5 wt.% were fabricated adopting in-situ polymerization technique. Partial discharge (PD) aging measurements were made and PD characteristic parameters were obtained to analyze the electrical performance of both neat PI and PI nanocomposites. Based on microscopic structural analysis, it was found that PI nanocomposite sample experienced less structural damage in contrast with neat PI. Smaller and lesser number of voids were found in PI/TiO2 nanocomposites than that of neat PI in result of PDs reduction in PI nanocomposite.

Investigation on thermally aged natural ester oil for real‐time monitoring and analysis of transformer insulation

Thermal aging of natural ester oil shows drastic reduction in partial discharge inception voltage (PDIV) and a significant variation is observed only above a certain aging time, under AC, DC, high frequency AC voltages and with harmonic voltages with different total harmonic distortion. Weibull distribution studies on PDIV measurements indicate a reduction in scale parameter (α) with increase in thermal aging temperature. A characteristic reduction in breakdown voltage was observed with the thermally aged ester oil, under AC, DC and standard lightning impulse voltage. The breakdown voltage variation with aged ester oil follows normal distribution. Ultraviolet (UV) analysis of ester oil thermally aged at 160°C has revealed a regular shift of the derived absorbance parameter to longer wavelengths. The interfacial tension and turbidity exhibits an inverse relationship with the thermally aged ester oil. Gas chromatography/mass spectrometric analysis of the thermally aged ester oil predicted the formation of more carboxylic acids and ketones with aging duration. The steady-state fluorescence on thermally aged ester oil exhibits a shift in its emission profile, which is in tandem with the UV absorption spectroscopic analysis. Fluorescence analysis can be adopted as a real-time monitoring tool in transformers, to understand the condition of liquid insulation. The viscosity dependence on the wavelength of derivative absorption maxima follows a direct relationship with the thermally aged natural ester oil.

Wireless Battery Charging Circuit Using Load Estimation Without Wireless Communication

A wireless battery charging circuit is proposed, along with a new load estimation method. The proposed estimation method can predict the load resistance, mutual inductance, output voltage, and output current without any wireless communication between the transmitter and receiver sides. Unlike other estimation methods that sense the high-frequency AC voltage and current of the transmitter coil, the proposed method only requires the DC output value of the peak current detection circuit at the transmitter coil. The proposed wireless power transfer (WPT) circuit uses the estimated parameters, and accurately controls the output current and voltage by adjusting the switching phase difference of the transmitter side. The WPT prototype circuit using a new load estimation method was tested under various coil alignment and load conditions. Finally, the circuit was operated in a constant current and constant voltage modes to charge a 48-V battery pack. These results show that the proposed WPT circuit that uses the new load estimation method is well suited for charging a battery pack.

Conceptual study on Grid-to-Vehicle (G2V) wireless power transfer using single-phase matrix converter

<span>This paper presents the conceptual study on grid-to-electric vehicle (G2V) wireless power transfer (WPT) using Single Phase Matrix Converter (SPMC). In this work, the SPMC is used as a direct AC to AC converter to convert the input supply voltage at 50 Hz frequency to the output of 20 kHz to meet the WPT switching frequency operation of the transmitter and receiver coils. The high frequency AC voltage of the receiver coil is then rectified to a DC form by using SPMC. Through the proposed system, the battery of an electric car can be charged wirelessly, thus removing the annoying wires of the conventional electric vehicle charging system. The reduction in size of the charging system, power losses and optimum efficiency are among the advantages of the proposed system. MATLAB/Simulink (MLS) has been used to simulate the proposed model. Selected simulation result are presented to verify the proposed work.</span>

Understanding the influence of nano micro filler on electrical and mechanical behaviour of epoxy nanocomposites

The study of epoxy nano micro composites clearly indicates that the material has better dielectric properties with a good discharge resistance and less surface charge accumulation on its surface. The impact of high-frequency AC voltage and the percentage of ripple content in DC voltage on corona inception caused by water droplets was analyzed. Under a high frequency, the variation in the shape of the water droplet is the same as that under 50 Hz AC voltage. The UHF signal radiated due to water droplet initiated discharges have signal bandwidth in the range of 300 MHz-3 GHz. The influence of corona discharge on surface properties of the material, its variation to contact angle and water droplet initiated corona activity under AC voltage was analyzed. The surface potential characteristics were altered with corona-aged specimen. The impact of an ion-trapping particle on nanocomposites clearly exhibits its characteristics through surface potential studies. Water diffusion into the insulating materials varies with the type of filler material. The temperatures measured during arcing, analyzed through laser-induced breakdown spectroscopy (LIBS), were correlated with the hardness of the material. In addition, the mechanical properties, especially storage modulus and tan δ, were analyzed through dynamic mechanical analysis (DMA) studies.

Toward flying qubit spectroscopy

While the coherent control of two level quantum systems ---qubits--- is now standard, their continuum electronic equivalents ---flying qubits--- are much less developed. A first step in this direction has been achieved in DC interferometry experiments. Here, we propose a simple setup to perform the second step, the spectroscopy of these flying qubits, by measuring the DC response to a high frequency AC voltage drive. Using two different concurring approaches --- Floquet theory and time-dependent simulations --- and three different models --- an analytical model, a simple microscopic model and a realistic microscopic model --- we predict the power-frequency map of the multi-terminal device. We argue that this spectroscopy provides a direct measurement of the flying qubit characteristic frequencies and a key validation for more advanced quantum manipulations.

Parameter Identification of Inverter-Fed Induction Motors: A Review

Induction motor parameters are essential for high-performance control. However, motor parameters vary because of winding temperature rise, skin effect, and flux saturation. Mismatched parameters will consequently lead to motor performance degradation. To provide accurate motor parameters, in this paper, a comprehensive review of offline and online identification methods is presented. In the implementation of offline identification, either a DC voltage or single-phase AC voltage signal is injected to keep the induction motor standstill, and the corresponding identification algorithms are discussed in the paper. Moreover, the online parameter identification methods are illustrated, including the recursive least square, model reference adaptive system, DC and high-frequency AC voltage injection, and observer-based techniques, etc. Simulations on selected identification techniques applied to an example induction motor are presented to demonstrate their performance and exemplify the parameter identification methods.

A Single-Stage Matrix-Based Isolated Three-Phase AC–DC Converter With Novel Current Commutation

An isolated single-stage three-phase ac–dc converter is proposed for aircraft system in this paper. The proposed converter uses the matrix ( $3 \times 1$ ) topology to directly convert three-phase line frequency ac voltages into high-frequency ac voltage, and therefore facilitates the use of high-frequency transformer for galvanic isolation leading to more compact and lighter weight of the power electronic converter. A space vector modulation-based switching scheme is proposed and digitally implemented for superior input power quality and improved power conversion efficiency. A current doubler rectifier (CDR) circuit is used at the output side, which essentially reduces the leakage inductance of the high-frequency transformer by decreasing the primary to secondary turns ratio. Moreover, an active soft-switched lossless snubber circuit is proposed to overcome the high voltage spikes produced due to the leakage inductance of the high-frequency transformer. A novel approach of adding a series capacitor in the primary winding of the high-frequency transformer for the soft and uninterrupted commutation of the high-frequency ac current is presented. The modes of operation of the proposed converter with the CDR circuit are analyzed in detail. Subsequently, the design equations for the proposed converter are derived. Simulation and experimental results are presented for a 500-W prototype converter suitable for aircraft systems.

Field emission properties of a DWCNT bundle and a single MWCNT

The field emission properties of a bundle of double-walled carbon nanotubes (DWCNTs) and a single multiwalled carbon nanotube (MWCNT) were investigated. A DWCNT bundle or a single MWCNT was attached to the head of sharpened tip of tungsten by electrophoresis; the tungsten tip was dipped into a drop of a carbon nanotube/1,2-dichloroethane suspension on a stainless plate, and a high-frequency AC voltage (20 V peak to peak with a frequency of 15 MHz) was applied between the tungsten tip and the stainless steel plate. The turn-on fields of the DWCNT and MWCNT tips for 1 nA/cm2 were 0.05 and 0.48 V/μm, respectively. From the Fowler-Nordheim plots, the field enhancement factor (β) of the tips was estimated to be 109,600 (DWCNT) and 6780 (MWCNT). The present DWCNT emitter is characterized by a very small turn-on field and large β. The field emission performance is discussed in terms of the sizes of the bundle of DWCNTs and a single MWCNT.

Experimental Challenges when Measuring Partial Discharges under Combined DC and High Frequency AC Voltage

The present paper reviews some of the challenges involved in designing and building an experimental setup for measurement of partial discharge under combined AC and DC voltage. A design of a modular test cell is discussed, as well as all parameters relevant to proper control of the experiment conditions. The described experimental setup is capable of producing sinusoidal AC voltage at a variable frequency up to 5 kHz superimposed a high DC voltage. The challenges related to intermittent noise reduction was remedied by placing the setup in a Faraday cage and controlling the setup from the outside by optical cables. All equipment in the test setup was connected to the power grid through low-pass filters.