Direct Current Test Research Articles

Emission characteristics of pulse CNT cold cathode X-ray source combined with channel electron multiplier

Carbon nanotube (CNT)-based field emission X-ray source with the advantage of fast start-up response offers the chance to achieve high-frequency X-ray emission. In this study, a high-frequency random pulse X-ray source of CNT cold cathode combined with a channel electron multiplier (CEM) was built, and its direct current (DC) and pulse emission characteristics were tested. The DC measurement results were used for parameter selection for performing pulse experiments. During the DC test, with the conditions of 2.2 kV CEM bias voltage and 25 kV anode voltage, the anode currents are 141, 250, and 300 μA at grid voltages of 290, 387.6, and 432.2 V, respectively; the corresponding grid field values are 1.45, 1.94, and 2.16 V/μm. During the pulse test, the amplitude–frequency response of the X-ray source reaches 3.58 MHz at 3 dB. The developed pulse X-ray source was introduced into the X-ray communication (XCOM), and the experimental communication rate reached 6 Mbps with the bit-error-rate of 1.1 × 10−3. The developed high-frequency pulse CNT-CEM X-ray source has potential applications in XCOM, high-speed X-ray imaging, and other fields.

Effect of electric current on porosity of concrete

The paper describes the influence of electric current on the porosity of concrete samples after electrically accelerated tests and other electrokinetic treatments. Three different concrete mixtures consisting of CEM I 42.5R, CEM II / A-M(S-LL) 42.5R, and CEM I 42.5R with 10 % replacement of cement by microsilica were examined. Direct current (DC) test was performed on fully saturated samples. The samples were loaded with a constant voltage of 20 V for 24 hours in chambers filled with NaOH solution. The changes in porosity were examined using mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and open porosity (OP). The results of open porosity indicate an increase in porosity for all mixtures measurements of ∼0.6 %–2 % for treated samples. The MIP showed increase of volume of pores with radius smaller than 0.01 μm after DC test. According to X-ray diffraction (XRD) and Thermogravimetric analysis (TGA) there was ∼2 % less calcite after DC test.

Electrical Equivalent Circuit Model Prediction of High-Entropy Alloy Behavior in Aggressive Media

Due to the optimistic outcomes of the research on high-entropy alloys, new designs of these alloys are being encouraged. We studied the high-entropy CoCrFeMoNi alloy and the CoCrFeMoNi alloy doped with Zr. In order to choose the best electrical equivalent circuit for the prediction of the behavior of these high-entropy alloys at various potentials in artificial seawater, electrochemical impedance spectroscopy (EIS) measurements were conducted on samples with and without Zr-doped CoCrFeMoNi. At various potential levels, the impedance spectra were measured between −1.0 and +0.8 V vs. SCE. The study consists of a preliminary section with microstructure by metallography, open-circuit potential, and linear polarization curves by direct-current tests followed by visual analysis of the impedance spectra, and, finally, the selection of an equivalent electrical circuit model to fit the experimental data. By leveraging the advantages of EIS analysis, the information is essential for materials development, corrosion-mitigation strategies, and the successful implementation of these alloys in practical applications. It is important to note that selecting an equivalent circuit is often an iterative and subjective process, as it involves a balance between model complexity and the ability to accurately represent the system’s behavior.

Experimental Study on Electric Harvesting of Combine Harvester

The electrification and intelligent transformation of harvester to make it have independent operation ability is an important embodiment of the development trend of agricultural automation and intelligence. Based on a full feed combine provided by relative company, this paper makes an electric transformation for its reaping and threshing part, including mechanical design, electric circuit construction, brushless DC(Direct Current) motor installation and test. Based on the finite automatic state mechanism, the control system of the electric operation part is built. Its sequential start and stop functions, reel speed following function and blockage detection and discharge function are tested in no-load experiment and farmland harvesting experiment. Through the continuous wheat harvesting test for 30 minutes, the power characteristics when harvesting wheat are measured, and the stability of its work is verified.

Characterization of micro-ZnO/PDMS composite structured via dielectrophoresis – Toward medical application

This paper proposed a new approach to achieve full characteristic of highly non-linear current density–electric field (J-E) curve, which depends on various key factors in terms of filler concentration, temperature, input voltage level, and structuration of ZnO particles (i.e. aligned or randomly dispersed). The homogeneity of particle distribution within the polymer matrix, together with the chain-like structure of the aligned composites elaborated with various ZnO volume fraction was verified via microscopic investigations. Numerical simulation was also conducted through COMSOL Multiphysics, giving an estimation of field distribution around ZnO phase. Experimental characterization in addition to analytical models was established using varying (sinusoidal) or direct current (DC) tests. The DC test was carried out in order to identify the conduction profile as well as the percolation threshold of ZnO samples. Temperature also has considerable influence on the switching field and the dielectric permittivity of the nonlinear composites. In the sinusoidal test, current discrimination was adopted using bipolar polarization loop, allowed the detailed quantification of conductivity values, while prediction in the capacitive current density enabled to distinguish the relative permittivity. These results demonstrated that the electrical properties of ZnO compound, such as conductivity and permittivity, substantially enhanced with the increasing filler content, especially when the samples were subjected to dielectrophoretic manipulation. Further analysis was carried out on sinusoidal unipolar polarization to predict the dielectric loss factor as function applied field. Finally, by playing on different pertinent parameters, it was possible to efficiently control the electric and mechanical characteristics of ZnO composite. Such properties are highly important in application of microvaristors used as protection devices. By associating with other features of ZnO like piezoelectricity, this material is undoubtedly of high interest in medical use where multifunctional system design becomes mandatory.

Partial Discharge Analysis and Simulation Using the Consecutive Pulses Correlation Method

The behaviour of partial discharge as consequences of an alternating current (AC) is already well defined. AC partial discharges have completely different behaviour, background physics and parameters than partial discharges (PD) under direct current (DC) stress. This paper focuses on the most used and promising evaluation method of the PD DC stress—pulse sequence analysis (PSA). The first step is understanding and verifying the mechanisms and principles of this method. It is provided by well-known fundamentals of AC PD and by comparison with the other diagnostic and fault-locating methods such as phase-resolved partial discharge (PRPD) and pulse diagrams. The paper shows the PSA simulations and PD analyses performed at AC and partly at DC test conditions on typical PD test arrangements such as corona, surface and internal discharges. It is shown that the simulations performed, compared and validated with data obtained from measurements on different PD arrangements are a good match. This fact opens the way for the PD source recognition in DC, especially the time-resolved pulse sequence analysis described in detail in the paper.

Effects of different kinds of carbon black nanoparticles on the piezoresistive and mechanical properties of cement-based composites

Carbon black nanoparticles (CBN) of different sizes, morphologies, microstructures and surface areas can be used to develop cement-based materials for strain monitoring and damage detection of concrete structures. There is a lack of systematic comparisons between mechanical and electrical properties of smart mortars fabricated with CBN of different characteristics. In this study, (4 × 4 x 7.5) cm prismatic composites containing CBN of distinct dibutyl phthalate (DBP) absorption number, conductivity and surface area were produced and subjected to direct current (DC), biphasic DC, piezoresistive and compression tests. Results show that CBN aggregates with the lowest structure (DBP of 125 cm³/100 g) and the highest resistivity provided high values of gauge factor, stress sensitivity and compressive strength, while CBN aggregates with very high structure (174 cm³/100 g) and low resistivity provided low internal capacitance and high electrical conductivity. The experimental data indicated that increases in structure and surface area improved the conductive network and reduced the internal capacitance, but decreased both compressive strength and piezoresistive response, due to reductions of variations of tunneling resistance between nanofillers.

Humidity Robustness of Plasma-Coated PCBs

The reliability of printed circuit boards (PCB) is at risk due to continuous miniaturization. As a result, PCBs are more susceptible to external factors such as humidity, temperature, contamination, etc., which affect their general performance, leading to failure of electronic devices. Therefore, protection of the devices against these factors is gaining greatly in importance. Plasma polymerization is used as a method to form a protective barrier by applying plasma polymer films on PCBs. However, the humidity robustness of such plasma coatings on the PCB surface is unknown. In this work, several methods were used to characterize two types of plasma-coated PCBs based on 1H,1H,2H-perfluorodecyl acrylate precursor (single-layer and stacked coatings) upon exposure to humidity, temperature, and bias voltage. Modulated-temperature differential scanning calorimetry enabled thermal analysis of the plasma coatings. Electrochemical impedance spectroscopy in combination with the gravimetric moisture vapor sorption technique were used to study the interaction of these coatings with moisture and quantify the water uptake. The results revealed an only 2% increase of the capacitance of the coatings due to water uptake. Direct-current (DC) leakage current measurements were used to study the influence of a bias voltage applied between the electrodes on the coated PCBs upon exposure to cyclic climatic conditions. Electrical DC testing revealed the protective character of the stacked coating, which did not fail under the given stress conditions, in contrast to the single-layer plasma coatings.

Contact arc time – important parameter of DC high-speed circuit-breakers

The parameters of DC high-speed circuit-breakers (HSCB) and test methods are specified in the standards. These standards define requirements of the circuit breakers opening time and the total breaking time. During the direct current (DC) breaking after opening the contacts, the arc ignites, the voltage of which is so low that it does not limit the switched off current. The time in which this phenomenon occurs is defined as the contact arc time.The contact arc time has a significant influence on the breaking process. It can take up to over 40% of arcing time. Therefore, tests were carried out, which were to answer the questions about what and to a what extent affects the contact arc time.Since the standards for high-speed circuit-breakers do not refer to the contact arc time, definitions of this parameter are proposed in the article. Using this definition numerous tests of various factors have been carried out on contact arc time.The conducted research shows that shortening the DC breaking time through high-speed breakers is possible by limiting the contact arc time, which can be obtained by modifying the circuit breaker’s construction.

Mechanical and electrical performance characterization of partial mock-up of the ITER PF6 coil tail

International Thermonuclear Experimental Reactor (ITER) is a full superconducting coil tokamak. The tail is an important component of Poloidal Field (PF) coil, of which the main functions are to provide the electrical isolation and transfer the longitudinal load from the last turn to the last-but-one turn. The paper focuses on an optimized mechanical structure of PF6 coil tail, which is made up of two main parts. One was welded to the last turn and the other was welded to the last-but-one turn. Both of them were connected by the mechanical coupling. The electrical isolation between the two parts was maintained by a strap made of insulating composite. In addition, as the PF6 coil is operated under the cyclic electromagnetic load during the tokamak operation, the fatigue property of the tail should be assessed and qualified at low temperature. Moreover, taking into consideration the complexity of the insulation winding process which is performed in a confined space, the wrapping process of the insulation needs to be established. Meanwhile, the high voltage (HV) tests of the tail insulation, including the direct current (DC) and alternating current (AC) tests, need to be assessed before and after the fatigue test.In this paper, a fully bonded PF6 coil tail partial mock-up (not including the weld of the tail to the last conductor turn) was designed and manufactured by simulating the actual manufacturing processes. In addition, the fatigue tests on the sample were carried out at 77K, and the results showed the sample had good and stable fatigue properties at cryogenic temperature. The HV tests before and after the fatigue test, also including the final 30kV breakdown DC test after the fatigue test, were carried out. The test results satisfied the requirements of ITER and were discussed in depth. Finally, the sample was destructively inspected to validate the integrity of the insulation by mechanical cross sectioning, and no voids and cracks were observed. Therefore it can be verified from the test results that the designed PF6 coil tail has good comprehensive properties, which can be applied to the formal production of the PF6 coil.

Development of a sensor for corona current measurement under high-voltage direct-current transmission lines

A sensor-based distributed measurement system is designed for collecting and monitoring the corona current under the extremely high-voltage direct-current transmission lines. It is highly significant for researching the corona characteristics of extremely high-voltage direct-current transmission lines to reduce the corona effect, operating loss, and environmental impact. A new shared memory strategy has been studied based on field-programmable gate array and ARM. Based on field-programmable gate array technology, the fiber-optic transmission scheme for wide-frequency corona current high-speed signal has been set up to ensure the safety and the reliability of corona current measurement system. The proposed system has been used in China’s state grid high-voltage direct-current test base and the in situ power transmission projects. Based on the experimental results, the proposed measurement system demonstrates that it can adapt to the complex electromagnetic environment under the transmission lines and can accomplish the accurate, flexible, and stable demands of the electric-field measurement.

Development of Data Acquisition Management System for ITER DC Testing Platform

To acquire multi-channel signals with 10 kHz sampling rate from various front-end sensors, a Data Acquisition Management System (DAMS) based on MDSplus was designed for the International Thermonuclear Experimental Reactor (ITER) Direct Current (DC) testing platform. Due to a large number of experimental data generated from long-pulse operation, it is very important to view and analyze experimental data online during operation. To meet the requirement of online data processing, slice storage and thumbnail technology were applied in DAMS. The long pulse data is gradually written in MDSplus database. The DAMS has been verified in the ITER DC power supply testing platform.

Torque Estimation Using Precise Calculations of Inductance and Iron loss Mathematization

Abstract – The torque was calculated with inductance and iron loss. Because the linkage flux can change the inductance, and q-axis current can change the iron loss. Therefore, precise estimation of torque can achieve with the inductance and iron loss detail calculations. So, in this paper, the d, q-axis inductance was verified through CVCT(Current Vector Control Test) and DCT(Direct Current Test). Also in the iron loss calculation, the prediction of all areas of current magnitude, phase angle and speed was very difficult. And LUT(Look-Up Table) was spent time and resource largely. Therefore, iron loss mathematization was proposed according to current magnitude, phase angle and speed. Also, characteristics of IPMSM were comprised of analyzed and experimental values. Keywords: d, q -axis inductance, Iron loss mathematization, Torque, Linkage flux 1. Introduction speed. Because, the iron loss should respond very quickly Generally, operating characteristics of IPMSM

Electromigration of Cu interconnects under AC and DC test conditions

Electromigration (EM) of a dual damascene, test vehicle was measured using direct current (DC), alternating current (AC) followed by DC, and three rectangular-wave DC stressing conditions at 598K. In some of the experiments samples were allowed to cool to room temperature between the 598K stress cycles. We find that that only net DC time at test has a significant effect on time to fail. AC stressing for one week at 2.5MA/cm^2 prior to DC stressing to EM failure had no effect on the EM performance. A similar result is obtained with various DC and thermal cycling conditions. Thermal history of the EM test samples, and in particular cooling to room temperature, has no effect on EM lifetime. All tests, regardless of thermal history and current cycling conditions, resulted in statistically similar times to fail and distributions of those times. We conclude that the standard test methodologies, using accelerated DC stress conditions at elevated temperatures, are adequate. Since only the net DC stress time had any measurable effect on EM lifetime, the use of accelerated testing provides a good predictor for lifetime expectations under operating conditions. We also conclude that neither low current density AC stressing nor DC cycling, and associated changes to grain structure that may result, provide any measurable benefit to EM lifetime.

Ultra High Voltage Transmission in China: Developments, Current Status and Future Prospects

The developments and current status of ultra high voltage (UHV) alternating current (AC) and direct current (DC) transmission in China were reviewed in this paper. The UHV transmission historical developments in the past twenty years; the demand of development UHV transmission; the research results of the UHV key technologies including electromagnetic environment, over-voltage and insulation coordination, lightning performance, live-line working and equipment manufacture recent years in China; the design parameters and construction of UHV AC, UHV DC test and demonstration transmission lines, UHV AC, DC test bases and state grid simulation center were introduced. The suggestions at the aspects of UHV transmission future design, construction, commercial operation and maintenance were simply presented and discussed. The review and discussion are important for the safe and reliable operation of UHV grid in China and can be a reference for other countries that want to develop UHV AC and DC transmission.

Digital simulation of source-insulator interaction in HVDC pollution tests

A technique is presented for digital computer simulation of the interaction between a polluted insulator and a high-voltage, direct-current test source. Both uncontrolled and feedback-controlled voltage-double sources are considered. The polluted insulator is represented by one or more arcs in series with the wet conducting layer. The arc is represented by a simple dynamic equation, and an attempt is made in the model to account for thermal phenomena in the unbridged wet layer. The simulation technique is then used to investigate the effect of the DC source parameters on the error obtained in the insulator flashover voltage. Both the effects of maximum and mean dynamic voltage drops are studied. It is shown that the approach applies well for both controlled and uncontrolled sources, while the effect of an external damping resistor is treated separately. Wherever possible the simulation results are compared to experiments, and in view of the complexity of the problem, the agreement is satisfactory. >

Technical Evaluation of Test Procedures for Insulated Aerial Devices Rated Less Than 69 kV

Alternating-and direct-current test procedures prescribed by American (ANSI A92.2-1969) and Canadian standards (CSA C225-1976) are evaluated using analytical methods and test results. It is demonstrated that the alternating-current (AC) technique is not adequate to evaluate the dielectric integrity of insulated booms. The direct-current (DC) technique, offered as an alternative by the Canadian standards, generally allows evaluation of overall material quality but not the identification of local defects such as cracks, scratches, voids, etc. For the time being, however, the DC test procedure is recommended although for the immediate future, a research effort will be required to develop a technique for adequate electrical evaluation of insulated aerial devices.

Technical Evaluation of Test Procedures for Insulated Aerial Devices Rated Less Than 69 kV

Alternating-and direct-current test procedures prescribed by American (ANSI A92.2-1969) and Canadian standards (CSA C225-1976) are evaluated using analytical methods and test results. It is demonstrated that the alternating-current (AC) technique is not adequate to evaluate the dielectric integrity of insulated booms. The direct-current (DC) technique, offered as an alternative by the Canadian standards, generally allows evaluation of overall material quality but not the identification of local defects such as cracks, scratches, voids, etc. For the time being, however, the DC test procedure is recommended although for the immediate future, a research effort will be required to develop a technique for adequate electrical evaluation of insulated aerial devices.

A Data System for High-Voltage DC Test Lines

An automatic data gathering and processing system for ??600-kV direct-current test lines at the National Research Council of Canada is described. The data consist of corona-loss current, radio interference, meteorological information, line voltage, and real time. The system consists of a 16-channel analog multiplexer, an A/D converter, a real-time clock, and a teletypewriter. All data are recorded on magnetic tape in IBM compatible format. A small stored-program digital computer controls the data system. The reasons for choosing the computer-controlled system for this application, a description of instrumentation for measuring the weather variables, and methods for telemetering corona-loss current information across the high-voltage barrier are included.

Test Line Experience with HVDC Overhead Transmission

Tests were conducted on a high-voltage overhead direct-current test line. Values of radio interference and corona loss were established for certain conductor configurations and pole spacings. Relations between radio interference and corona loss and some weather variables were evaluated. Insulator leakage currents and induced overhead ground wire currents were investigated.