Voltage Current Waveforms Research Articles

Calibration of On-Board Energy Measurement Systems Installed in Locomotives for AC Distorted Current and High Voltage Waveforms and Determination of Its Uncertainty Budget.

Periodic calibrations of Energy Measurement Systems (EMS) installed in locomotives must be carried out to demonstrate the required accuracy established in the EN 50463-2 standard according to European Parliament and Council Directive 2008/57/EC on the interoperability of rail systems within the Community. As a result of the work performed in the “MyRailS” EURAMET project an AC calibration facility was developed consisting of a fictive power source was developed. This fictive power source can generate distorted sinusoidal voltages up to 25 kV-50 Hz and 15 kV-16.7 Hz as well as distorted sinusoidal currents up to 500 A with harmonic content up to 5 kHz or phase-fired current waveform stated in EN50463-2 standard. These waveforms are representative of those that appear during periods of acceleration and breaking of the train. Reference measuring systems have been designed and built consisting of high voltage and high current transducers adapted to multimeters, which function as digital recorders to acquire synchronized voltage and current signals. An approved procedure has been developed and an in-depth uncertainty analysis has been performed to achieve a set of uncertainty formulas considering the influence parameters. Different influence parameters have been analyzed to evaluate uncertainty contributions for each quantity to be measured: rms voltage, rms current, active power, apparent power and non-active power of distorted voltage and current waveforms. The resulting calculated global expanded uncertainty for the developed Energy Measuring Function calibration set up has been better than 0.5% for distorted waveforms. This paper is focused on presenting the complete set of expressions and formulas developed for the different influence parameters, necessary for uncertainty budget calculation of an Energy Measuring Function calibration.

Cascaded Boost AC-AC Converter with High-Gain Voltage

This paper presents cascaded boost AC-AC converter with control strategy. The proposed system can attain high-gain voltage by using low-voltage rating switch devices. The control technique leads to nearly unity power factor and the required high voltage at stop working unit (SWU). The output voltage can be controlled up to double the input voltage multiplied by the number of units. The proposed converter has many advantages such as, low number of semiconductor switches, nearly sinusoidal output voltage, and negligible distortion in the supply current and load voltage waveforms. The proposed cascaded converter is suitable to be extended because all the AC - AC converter units have similar construction, control strategy, and operating conditions. Accordingly, maintenance is simple and the defective unit can be easily detected and compensated. The prototype converter with several numbers of units is constructed and tested to verify the performance. The proposed circuit and control technique is validated by the simulation results with MATLAB software.

Discharge characteristics and reactive species production of unipolar and bipolar nanosecond pulsed gas–liquid discharge generated in atmospheric N2

In this paper, unipolar pulse (including positive pulse and negative pulse) and bipolar pulse voltage are employed to generate diffuse gas–liquid discharge in atmospheric N2 with a trumpet-shaped quartz tube. The current–voltage waveforms, optical emission spectra of excited state active species, FTIR spectra of exhaust gas components, plasma gas temperature, and aqueous H2O2, and production are compared in three pulse modes, meanwhile, the effects of pulse peak voltage and gas flow rate on the production of reactive species are studied. The results show that two obvious discharges occur in each voltage pulse in unipolar pulse driven discharge, differently, in bipolar pulse driven discharge, only one main discharge appears in a single voltage pulse time. The intensities of active species (OH(A), and O(3p)) in all three pulsed discharge increase with the rise of pulse peak voltage and have the highest value at 200 ml min−1 of gas flow rate. The absorbance intensities of NO2 and N2O increase with the increase of pulse peak voltage and decrease with the increase of gas flow rate. Under the same discharge conditions, the bipolar pulse driven discharge shows lower breakdown voltage, and higher intensities of excited species (N2(C), OH(A), and O(3p)), nitrogen oxides (NO2, NO, and N2O), and higher production of aqueous H2O2, and compared with both unipolar positive and negative discharges.

Power quality evaluation of photovoltaic grid interfaced cascaded H-bridge nine-level multilevel inverter systems using D-STATCOM and UPQC

The enhancement in Power Quality (PQ) becomes essential to increase the overall performance of equipment in utility-grid tied systems. To enhance PQ, this paper enumerates operational impact of Distribution Static Compensator (D-STATCOM) and Unified Power Quality Conditioner (UPQC) into a cascaded H-bridge Nine-Level Multi-Level Inverter (NL:MLI). The effectiveness of proposed topology is evaluated at a constant 200 V DC voltage and two SPV arrays of 100 kW each. A PQ comparative analysis is presented under faulted conditions at linear load. In order that the proposed system operates effectively under changing environment conditions, the implementation of a competent control techniques is dominant. Consequently, the control approach for D-STATCOM and UPQC compensates reactive power requirement of load and utility-grid. Total Harmonic Distortion (THD) and DC offset current are estimated, with distortion-less current-voltage waveforms obtained at coupling points. THD levels are validated in agreement with IEEE-519 standard. Indeed, the effectiveness of UPQC is demonstrated by feeding excess power through SPV arrays into variable DC link. Overall, the operation of UPQC interfaced with NLMLI is effective over D-STATCOM in alleviatin g harmonics, DC-offsets, and voltage-current imbalances during faulted conditions. The accurateness of simulation results and their comparative analysis is found to be satisfactory.

Non-thermal plasma multi-jet platform based on a flexible matrix.

A new plasma source design that merges the main characteristics of capacitive dielectric barrier discharge (DBD) and cold atmospheric plasma jet (CAPJ) is discussed. The DBD system contains a flexible, porous matrix consisting of silica aerogel, which is comprised between two biased electrodes. The helium flow supply subjected to a sinusoidal voltage of around 5 kV in amplitude and 15 kHz in frequency provides a set of plasma jets that propagates more than 1cm beyond the active DBD region. The studied plasma multi-jet system consists of an array of three aligned jets that flow in the laminar regime, and it is intended for treating the surfaces of 3D objects and large areas. CAPJ performance is discussed as a hypothetical morphing source in flat and bent configurations. Electrical characterization and optical emission spectroscopy diagnostics have provided current-voltage waveforms and the composition of the CAPJ through the aerogel layer, respectively. This novel source is promising for biomedical applications that require full adaptation of plasma parameters to delicate samples, such as wound healing and treatment of surgical margins in plasma-based cancer surgery.

The Effect of Oxygen Admixture with Argon Discharges on the Impact Parameters of Atmospheric Pressure Plasma Jet Characteristics

Dry argon (Ar) discharge and wet oxygen/argon (O2/Ar) admixture discharge for alternating current atmospheric pressure plasma jets (APPJs) were studied for Ar discharges with flow rates ranging from 0.2 to 4 slm and for O2/Ar discharges with different O2 ratios and flow rates ranging from 2.5 to 15 mslm. The voltage–current waveform signals of APPJ discharge, gas flow rate, photo-imaging of the plasma jet length and width, discharge plasma power, axial temperature distribution, optical emission spectra, and irradiance were investigated. Different behavior for varying oxygen content in the admixture discharge was observed. The temperature recognizably decreased, axially, far away from the nozzle of the jet as the flow rate of dry argon decreased. Similar behavior was observed for wet argon but with a lower temperature than for dry argon. The optical emission spectra and the dose rate of irradiance of a plasma jet discharge were investigated as a function of plasma jet length, for dry and wet Ar discharges, to determine the data compatible with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) data for irradiance exposure limits of the skin, which are suitable for the disinfection of microbes on the skin without harmful effects, equivalent to 30 μJ/mm2.

Multiple current pulse behavior and its dynamics of atmospheric pressure plasma jet in a needle-to-ring configuration

The characteristics of an atmospheric pressure plasma jet (APPJ) based on needle-to-ring dielectric barrier discharge (DBD) have been investigated experimentally. The plasma jet is driven by a sinusoidal voltage, and the working gas is argon. The jet length, the voltage-current waveforms, the optical emission spectra and the plasma evolution have been studied. Moreover, the transferred charges of the discharge pulse and the electron excitation temperature were investigated. These results reveal that there exist two or more current pulses per half-cycle as the applied voltage increases. In fact, the multiple current pulses correspond to multiple breakdowns between the electrodes. This phenomenon in DBD-APPJ is mainly attributed to the surface charges on the grounded ring electrode surface, which can induce a strong reverse electric field to counteract the applied electric field. In addition, the jet length is extended stepwise as the number of current pulses increases. The residual excited species or charges remaining from the previous discharge play an essential role in the formation of a stronger next discharge and are responsible mainly for a higher electron excitation temperature, which makes the jet develop farther (i.e., a longer jet). Finally, we obtain a preliminary control condition to switch a single current pulse into multiple pulses, which has a benefit for industrial applications.

A Simplified Model of a Surge Arrester and Its Application in Residual Voltage Tests

A simplified and accurate model of a surge arrester used in the residual voltage test is proposed in this paper. With the help of a genetic algorithm, the measured impulse current and residual voltage waveforms are utilized to determine circuit parameters of the proposed model and the generation circuit precisely. The technique starts from the circuit parameter determination using the preliminary experimental data with a lower current peak than that specified by the standard. From the determined model and with the help of the genetic algorithm, the circuit parameters and the charging voltage to obtain the specified current peak and the residual voltage can be estimated accurately. The validity of the proposed technique has been verified by experiments for the estimation of the appropriate current circuit parameters, the charging voltage, and the residual voltage. In addition, the application of the proposed model in the residual voltage tests is presented. From comparison of simulated and experimental results with the determined parameters, the impulse current and residual voltage waveforms are determined precisely. It is confirmed that the proposed model and technique are attractive in the appropriate circuit parameter determination and the residual voltage estimation in the residual voltage tests of surge arresters. The proposed method also provides a good advantage for reduction of the number of trial and error experiments for obtaining the current waveform according to the standard requirement. Moreover, the unintentional damages of the arrester during the process of the waveform adjustment will be reduced significantly.

Improving arc stability during wire arc additive manufacturing of thin-walled titanium components

Fabrication of thin-walled titanium structures by a gas metal arc based wire arc additive manufacturing process is considered challenging due to arc instability. This instability is primarily caused by the cathode spot oscillations. In this work, attempts were made to improve the cathode spot stability by using a surface oxidised titanium feedstock. The deposition behaviour was analysed by a high-speed camera analysis under straight and reverse polarities. Current-voltage waveforms were suitably modified to achieve a stable short-circuiting transfer in bare and surface oxidised conditions. The surface oxidised wire was found to provide a stable arcing and reduction in arc wandering. Based on the correlation between current-voltage waveforms and metal transfer characteristics, optimum deposition procedures were identified to manufacture thin-walled titanium components.

Influence of droplet transfer behaviour on the microstructure, mechanical properties and corrosion resistance of wire arc additively manufactured Inconel (IN) 625 components

A Ni-based superalloy, Inconel 625, is widely used for aerospace, petrochemical and marine applications due to its excellent corrosion and elevated temperature mechanical properties. In this study, efforts were made to identify optimum deposition parameters to produce directionally solidified Inconel 625 components using wire arc additive manufacturing (WAAM). Components were deposited by short-circuiting and short-circuiting with pulse mode of droplet transfers using a commercial cold metal transfer gas metal arc welding (CMT-GMAW) power source. For a given arc energy, metal droplet transfer behaviour was studied using a high-speed camera. Microstructural analysis and corrosion resistance of Inconel 625 samples produced by WAAM and samples made by conventional casting process were compared by advanced characterisation methods. Inconel 625 samples produced using a combination of short-circuiting with pulsing free flight transfers showed improved mechanical properties than as-cast samples and samples made only by short-circuiting transfer due to the formation of directionally solidified coarse-grained columnar microstructure. Moreover, corrosion resistance of WAAM samples was found to better than that of as-cast samples. Based on the results, an optimised current-voltage waveform and droplet transfer modes were identified to produce defect-free Inconel 625 deposits with desired microstructure, and mechanical and corrosion-resistance properties.

Observation of Arc Behaviour in TIG/MIG Hybrid Welding Process

In this project, the influence of TIG currents’s variation on arc stability of TIG/MIG hybrid welding was studied by comparing with MIG welding process. The welding current-voltage waveform was analyzed to characterize the arc stability of the MIG arc. From the observations, the introduction of TIG arc as low as 60 A of current significantly change the MIG arc stability in TIG/MIG hybrid welding. The length of MIG arc in TIG/MIG welding increased with the introduction of the TIG arc as compared with MIG welding. The increase of arc length was due to the arc interaction between the TIG arc and MIG arc, which is affecting the wire melting rate. At the maximum TIG current, the diameter of the molten droplet decreased with the increment of droplet transfer frequency.

Preliminary Study of Harmonic Generated by Household Appliances

This paper is preliminary study with focused on the harmonics generated by household appliances. There are only several household appliances that considered in this paper are television set, laptop computer and compact fluorescent lamp (CFL). To measure the input current, the measurement equipment was installed at the input side of equipment under the test. The important parameters that have been recorded are individual harmonic currents, total harmonics distortion, power factor, input current and input voltage wave form. From the measurement results, television sets, laptop computers and CFLs have been found generate the THDi of 177%, 273.66% and 154.2% respectively. If it is widely used in residential areas, it is likely that there will be increased harmonic distortion in the electric power distribution system. Because this research is still in its early stages, at the end of this research it will be known how much harmonics is generated by the load in the residential area. If amount of harmonics generated by the housing load that exceeds the limit, so the next step of this research a harmonics filter design will carried out.

İki Seviyeli SPWM Evirici ile Tahrik Edilen Sabit Mıknatıslı Senkron Motorun Simülasyonu

In this study, a permanent magnet synchronous motor (PMSM) was driven by a two-level inverter modeled in MATLAB / Simulink environment. A simulation model has been created that can give results compatible with the results in real test setups. In order to obtain realistic results and waveforms, equivalent models were used instead of ideal models. For example, the use of PMSM electrical and mechanical equivalent models, adding resistance and inductance to the grid side, and modeling the DC bus capacitor with equivalent series resistance (ESR) will ensure the convergence of the obtained results to the results from real test setups. Open-loop control of PMSM has been provided. Gate signals required for semiconductor switches were produced by SPWM (Sinusoidal Pulse Width Modulation) switching method. The working principle of this PWM (Pulse Width Modulation) method has been studied in detail. In order to understand the structures on the inverter, simulation models, important parameters, and mathematical equations are given in the relevant sections respectively. In the given simulation outputs, the current-voltage waveforms of many important points on the inverter and PMSM were examined. Current drawn from the grid, voltage ripple on the DC bus capacitor, switching patterns produced by the SPWM method, inverter output phase currents, motor phase-to-neutral voltages, motor phase-to-phase voltages are the waveforms that are considered as important and presented within the scope of this study. In particular, the inverter output current-voltage signals are given for power calculation. After all these basic examinations, the inverter output power, as known as the motor input power, was measured. The phase angle between the motor phase current and phase-neutral voltage was found. Finally, these measurements made in the Simulink environment were compared with theoretical calculations and the accuracy of the models was proved.

Performance comparison of field oriented control based permanent magnet synchronous motor fed by matrix converter using PI and IP speed controllers

This paper focuses on modeling and closed-loop speed control of a three-phase Permanent Magnet Synchronous Motor (PMSM) fed by a Matrix Converter (MC) based on Field-Oriented Control (FOC). The model considers a set of a small input filter with supply impedance or cable effect, to improve the quality of the input current. A simplified form of the Venturini modulation algorithm is used for switching the matrix converter and a comparative study of two types of speed controllers is presented, namely a proportional integral (PI) and a proportional integral (PI) to improve performances of the drive system in transient and stable conditions. The overall drive system is simulated using Matlab/Simulink environment. The motor performance is evaluated under different operating conditions such as sudden changes in the load or changes in the angular speed reference. The results of the converter MC gives unlimited output frequency, sinusoidal input current and output voltage waveforms and unity input displacement factor. The IP controller is shown to achieve better performance of the speed control loop, with or without the load torque as compared to the PI classic controller.

Combined Properties of Al/Ni Reactive Multilayer Films During High-Rate Heating Using a Pulse of Current

We use pulses of current to investigate the combined properties of Al/Ni multilayer films under high-rate heating by measuring current-voltage waveforms and the flyer velocity. Explosion occurs earlier in the Al/Ni multilayer foil than in the Al and Ni films, suggesting that the addition of Al/Ni affects the electrical exploding process, which is not controlled solely by resistance. The experiments indicates that the differences between the physical properties of the Al and Ni films is a factor to causing higher plasma electron temperature and absorb more electrical energy than the single Al or Ni film. The flyer velocity of the Al/Ni multilayer film is much lower than that of the Al film due to the high adiabatic index of Ni.

Electrical characterization of positive and negative pulsed nanosecond discharges in water coupled with time-resolved light detection

Electrical discharge in liquids is a research field that has great potential in environmental and technological applications. Depending on the experimental conditions (liquid nature, interelectrodes distance, applied voltage, pulse width, etc.), various discharge modes can be obtained. The involved physical processes have relatively fast spatiotemporal dynamics and, therefore, are not well understood. In this study, we report the electrical characterization, coupled with time-resolved light detection (using a photomultiplier, PM, tube), of positive and negative pulsed nanosecond spark discharges in de-ionized water using copper electrodes (distanced by ∼50 μm) in a pin-to-plate configuration. A detailed analysis of the current–voltage waveforms during the pre-breakdown and the breakdown phases is shown, and we found that the pre-breakdown phase depends on the high voltage magnitude only for positive polarity. On the other hand, the PM signals showed dependence on the voltage magnitude and on the pulse width, and various emission phases are observed. These phases can be related to the discharge power and/or to the discharge current. Filtered PM signals at various wavelengths are also acquired, and their temporal dynamics are discussed regarding the discharge conditions.

Wire arc additive manufacturing of functionally graded material for marine risers

Functionally graded materials (FGM), whose structural properties are varied along their volume to perform an intended function, have a full application in the marine industry. Under the corrosive marine environment, a corrosion-resistant alloy of duplex stainless steel, functionally graded with carbon-manganese steel along with the inner layer, is proposed here for the risers. The interface strength of FGM, fabricated using Cold Metal Transfer – gas metal arc welding, based on Wire Arc Additive Manufacturing (WAAM) in the lab-scale, is compared with an X-52 Carbon Manganese steel to highlight the superiority of the proposed FGM. The role of metal transfer characteristics on the microstructure formation at the layers adjacent to the interface is analyzed and correlated with the voltage-current waveform those obtained during the deposition process. Based on the experimental studies carried out, it is seen that the yield strength of the FGM interface is very close to that of X52 steel, with a marginal increase of about 6% in the ultimate strength. Based on the energy dispersive X-ray analysis, it is observed that there is no enrichment of chromium across the interface towards the carbon-manganese steel side. It is vital for the corrosion-resistance of duplex stainless steel. Proposed FGM shows advantages both in strength and durability and hence seen as a promising candidate for marine riser applications.

High energy efficient degradation of toluene using a novel double dielectric barrier discharge reactor

A double dielectric barrier discharge (DDBD) reactor was established to decompose toluene with high energy efficiency. Differences in discharge characteristics including visual images, voltage-current waveforms, Lissajous figures, and temperature variation, were determined between the DDBD and SDBD reactors. Removal efficiency, mineralization rate, CO2 selectivity, and energy yield were used to evaluate the toluene abatement performance of the two reactors. Compared to the SDBD reactor, the DDBD reactor exhibited more uniform and stable discharges due to a change in discharge mode. In addition, the DDBD reactor’s dissipated power and reactor temperature (including the gas, barrier and ground electrode) were significantly lower than those in the SDBD reactor. At 22−24 kV, the DDBD reactor showed a higher toluene removal efficiency and mineralization rate, while at 14−16 kV, the SDBD reactor exhibited higher respective value. The energy efficiency of the DDBD was 2.5–3 times that of the SDBD reactor, and the overall energy constant koverall of the DDBD reactor (1.47 mL/J) was significantly higher than that of the SDBD reactor (0.367 mL/J) as revealed by the kinetics study. Lastly, a plausible toluene degradation mechanism in the DDBD and SDBD reactors was proposed based on organic intermediates that formed during toluene decomposition.

Cold Atmospheric Pressure Plasma Jet for the Improvement of Wettability of Polypropylene

This paper reports the generation of cold plasma jet working under atmospheric pressure condition, for surface treatment of polymeric films. The discharge has been characterized by electrical and optical methods. The electrical property of the discharge has been studied by taking current-voltage wave forms using voltage and current probes. The production of argon plasma jet is done in atmospheric conditions which are relatively much cheaper, convenient, and safer to use. The atmospheric pressure plasma jet sustained in pure argon has been used to improve wettability of polypropylene (PP). Cold atmospheric pressure plasma jet (CAPPJ) has been generated by a high-voltage power supply (5.5 kV, 0-20 kV) at an operating frequency of 20 kHz. The surface properties of the controls and plasma-treated PP samples were characterized by contact angle measurement, surface free energy measurement, scanning electron microscopy, and the Fourier transform-infrared spectroscopy analysis.

Effect of plasma main arc on droplet transfer in skew-coupling arc welding

Abstract A method of controlling droplet transfer by plasma arc was proposed to solve the problem that cathode spot force hindered the transition of cathode droplet under high current of twin-wire indirect arc (TWIA) in skew-coupling arc (SCA) welding. The effects of the plasma arc on droplet transfer were analyzed from the perspectives of plasma arc current (PAC) and plasma gas flow rate (PGFR). The current-voltage waveform, arc shape and the transition process of droplet were studied by using an electric signal and high-speed camera acquisition system. The results show that controlling droplet transfer by the plasma arc is feasible and effective in the SCA welding. With the increase of the PAC, the degree of the plasma arc deflection increased, and increasing the PGFR has a shrinkage effect on the top of the SCA. Increasing the PAC or the PGFR made the TWIA current vary in a small range, and the plasma arc voltage increase. Increasing the PGFR is more effective to promote the transition of cathode droplet than increasing the PAC, because the plasma fluid force of the TWIA on cathode droplet is enhanced by the double axial thrust of the plasma arc and the TWIA. The cooling effect of the plasma gas on anode droplet weakens the promoting effect of the plasma gas on the transition of anode droplet. The existence of the fluid beam hanging at the cathode wire is important to improve the transition of cathode droplet. The PGFR and the PAC could be cooperatively adjusted to promote the transition process of anode and cathode droplet.