Current Flow Time Research Articles

The influence of parameters of the resistance projection welding of M10 steel nuts to the galvanized steel sheet DP 600 on selected joint characteristics

Projection welding belongs to the group of resistance welding technologies. The basic process parameters are the welding current and the current flow time. Although the resistance projection welding of nuts on galvanized steel sheets is widely used in industry, only a few research articles have been published. The resistance projection weld-ability of the fasteners on metal sheets is not as well understood as the resistance spot weldability of the sheets, so complex studies for the wider application of resistance welding of nuts in the automotive industry are still needed. This research is aimed at valuation the effect of resistance projection welding parameters (steel nuts on galvanized steel sheet DP 600) on joint properties. The hard welding mode (high welding current, clamping force and short welding time) provided 2 times higher strength of the weld joints as the soft welding mode. When using the soft welding mode, an increased Zn concentration from the sheet metal coating was measured in the transition area between the welded materials at the folding locations. When applying the hard welding mode, only a slight in-crease in the Zn concentration was observed at the inner boundary of the weld joint.

Evaluation of Adhesiveness with Current Flow Time in the Indirect Heating of an Asphalt Pad using Joule Heating

Evaluation of Adhesiveness with Current Flow Time in the Indirect Heating of an Asphalt Pad using Joule Heating

Projection welding of nuts involving the use of electromechanical and pneumatic electrode force

The projection welding of nuts performed using the pneumatic (electrode) force system (PFS) was subjected to thorough numerical and experimental analysis, enabling the identification of the window of welding parameters taking into consideration boundary conditions including expulsion, torsional strength and the deformation of the nut thread. The welding process was subjected to optimisation involving the use of a new, i.e. electromechanical (electrode) force system (EFS). The optimisation-related approach involved the reduction of welding current and the extension of a welding current flow time in comparison with those obtained when using the pneumatic force system. It was assumed that the acceptance criterion would be the breaking torque not lower than that obtained under the most favourable welding conditions performed using the PFS. The research work involved comparative numerical calculations (performed using the SORPAS software) in relation to both, i.e. the PFS and EFS. The technological welding tests were performed using inverter welding machines (1 kHz) provided with various (electrode) force systems. The research work also included metallographic tests, hardness measurements and torsional strength tests. As a result of the application of EFS and a special innovative hybrid algorithm for controlling the electrode clamps, a wider and higher weld core was obtained. The depth of “penetration” into the sheet was greater. As a result, the welded joint has a higher resistance (by 30%). Technological welding tests for the new EFS system were carried out for a 25% lower welding current compared with PFS. Despite the lower welding current for EFS, the welding energy is slightly lower but the welding quality for EPS is significantly higher.

Recommendations for standardization of voltage level in LVDC networks based on IEC 60479-1 guidelines

In order to standardize the DC (direct current) voltage level in low voltage grids, a study is carried out considering the behavior of the human body against different DC voltage levels. The study is based on an analysis that determines if the amount of body current that flows under specific shock conditions is tolerable or not, keeping the current flow time in account. The body impedance is first calculated for two different DC voltage levels with different skin contact conditions. Possible current paths through the human body are subsequently considered to realize the best and worst-case scenario for human contact with live terminal. A relationship between touch voltage and source voltage is defined considering the grounding methods in DC systems. Using ventricular fibrillation curves, the maximum allowable body currents and the associated flow intervals for human bodies are analyzed for the selected voltage levels. The study makes a step further in addressing the feasibility and safety concerns for the standardization of DC voltage level for low voltage installations.

Joining of the AMC Composites Reinforced with Ti3Al Intermetallic Particles by Resistance Butt Welding

Abstract The introduction of new reinforcing materials continues to be investigated to improve the final behaviour of AMCs as well as to avoid some drawbacks of using ceramics as reinforcement. The present work investigates the structure, properties and ability of joining aluminium EN-AW 6061 matrix composite materials reinforced with Ti3Al particles by resistance butt welding as well as composite materials produced by mechanical milling, powder metallurgy and hot extrusion techniques. Mechanically milled and extruded composites show finer and better distribution of reinforcement particles, which leads to better mechanical properties of the obtained products. Finer microstructure improves mechanical properties of obtained composites. The hardness increases twice in the case of mechanically milled composites also, a higher reinforcement content results in higher particle dispersion hardening, for 15 wt.% of intermetallics reinforcement concentration composites reach about 400 MPa UTS. Investigation results of joints show that best hardness and tensile properties of joints can be achieved by altering soft conditions of butt welding process e.g. current flow time 1.2 s and current 1400 A. To improve mechanical properties of butt welding joints age hardening techniques can also be used.

Comparison of Density Tests for Thin Hot-Mix Asphalt Overlays

The thin overlay mix (TOM) and ultrathin overlay mix (UTOM) specifications in Texas test falling head water flow as a surrogate measure of density. Current flow time criterion has never been correlated to density; furthermore, there is no maximum flow time to prevent overcompaction. A rolling density meter (radar) and a circular track meter may also be used to measure thin lift density. These tests and traditional core testing were used on three projects, and the correlations between tests were analyzed. Correlations were strong on a project-by-project basis but generally poor when data sets were combined. Flow time and mean profile depth, flow time and core voids, and surface dielectric and core voids were the strongest correlations overall; measured voids were unusually high. The reliability of taking core measurements on such thin samples is questionable and may be overly influenced by the surface texture. The flow test should continue to be used as a surrogate measure of density. No minimum flow time was recommended because of unusually high void measurements. To avoid overcompaction in TOMs, flow time should be less than 6 min on higher-speed or critical sections and less than 10 min on lower-speed, noncritical sections. From the standpoint of macrotexture in the UTOM, no upper limit is recommended for flow time. The rolling density meter should be employed on project-specific issues when full-coverage density measurements are desired. Further testing should be conducted on the reliability of measuring voids on very thin cores.

Investigations on performance of ECDM process using NaOH and NaNO<SUB align="right">3 electrolytes while micro machining soda lime glass

Electro chemical discharge machining (ECDM) is a proven process for micro machining difficult to process non-conductive materials. The experimental results [material removal (MR) and tool wear (TW)], while fabricating shallow holes on soda lime glass using ECDM process; have been reported in the paper. The electrolytes viz. NaOH and NaNO3 were used during the micromachining on soda lime glass. The detailed parametric study was planned using the standard L9 orthogonal array. Influence of process parameters, namely electrolyte concentration, applied voltage, distance between electrodes and time of current flow on response parameter, i.e., MR were analysed. The results showed that NaOH was more efficient as compared to NaNO3. The results on MR showed that all parameters were significant and applied voltage was found to be the most influencing parameter (70.14%). Field emission scanning electron microscopy (FESEM) and debris analysis were further carried out to study the performance of the ECDM process.

Study of Superconductor Recovery Time Characteristics and High‐Speed Reclosing of Electromagnetic Repulsion Switch

AbstractUsing a high‐temperature superconductor, we constructed and tested a model superconducting fault current limiter (SFCL). The superconductor and a vacuum interrupter serving as the commutation switch were connected in parallel using a bypass coil. When the fault current flows in this equipment, the superconductor is quenched and the current is then transferred to the parallel coil due to the voltage drop in the superconductor. This large current in the parallel coil actuates the magnetic repulsion mechanism of the vacuum interrupter and the current in the superconductor is interrupted. Using this equipment, the current flow time in the superconductor can easily be minimized. On the other hand, the fault current is also easily limited by the large reactance of the parallel coil. This system has many advantages. Thus, we introduced an electromagnetic repulsion switch. High‐speed reclosing after interrupting the fault current in the electrical power system is essential. Thus, the SFCL should recover to the superconducting state before high‐speed reclosing. But the superconductor generates heat at the time of quenching, and it takes time to recover to the superconducting state. Therefore, the recovery time is an issue. In this paper, we study the superconductor recovery time. We also propose an electromagnetic repulsion switch with a reclosing system. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(3): 12–19, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21072

Operation of superconducting fault current limiter using vacuum interrupter driven by electromagnetic repulsion force for commutating switch

AbstractUsing conventional high‐temperature superconducting wire, a model superconducting fault current limiter (SFCL) is made and tested. Solenoid coil using Bi2223 silver sheath wire is so made that inductance is as small as possible and a vacuum interrupter is connected in series to it. A conventional reactor coil is connected in parallel. When the fault current flows in this equipment, superconducting wire is quenched and current is transferred into the parallel coil because of voltage drop of superconducting wire. This large current in parallel coil actuates magnetic repulsion mechanism of vacuum interrupter. Due to opening of vacuum interrupter, the current in superconducting wire is broken. By using this equipment, current flow time in superconducting wire can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of parallel coil. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 52–61, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20315

Study of Electromagnetic Repulsion Switch to High Speed Reclosing and Recover Time Characteristics of Superconductor

Using a high-temperature superconductor, we constructed and tested a model superconducting fault current limiter (SFCL). The superconductor and vacuum interrupter as the commutation switch were connected in parallel using a bypass coil. When the fault current flows in this equipment, the superconductor is quenched and the current is then transferred to the parallel coil due to the voltage drop in the superconductor. This large current in the parallel coil actuates the magnetic repulsion mechanism of the vacuum interrupter and the current in the superconductor is broken. Using this equipment, the current flow time in the superconductor can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of the parallel coil. This system has many merits. So, we introduced to electromagnetic repulsion switch.There is duty of high speed re-closing after interrupting fault current in the electrical power system. So the SFCL should be recovered to superconducting state before high speed re-closing. But, superconductor generated heat at the time of quench. It takes time to recover superconducting state. Therefore it is a matter of recovery time. In this paper, we studied recovery time of superconductor. Also, we proposed electromagnetic repulsion switch with reclosing system.

Study of kV Class Current Limiting Unit With YBCO Thin Films

Using a high temperature superconductor, we proposed a model superconducting fault current limiter (SCFCL) with the high-speed commutation switch. The high-speed commutation switch consists of the parallel coil, the electromagnetic repulsion plate and the vacuum interrupter. In this SCFCL, the current in the superconductor is interrupted within 0.5 cycles. By using this equipment, the current flow time in the superconductor can be easily minimized. We studied resistive type SCFCL with the high-speed commutation switch and use YBCO thin film. For applying to high voltage, it is a problem that the superconductors in series connection don't quench immediately for the Ic variations of the various superconductors. In this paper, we conducted the series connection test using YBCO thin films without a metal layer. The research is aimed at the scalability of small models towards commercial size fault current limiter (FCL).

인버터 에어컨 시스템의 역률보상을 위한 AC-DC 컨버터 제어

In this paper, we propose a new AC-DC converter control method to comply with harmonics regulation(IEC 61000-3) effective for the inverter system of an air conditioner whose power consumption is less than 2,500W. There are many different ways of AC-DC converter control, but this paper focuses on the converter control method that is adopting an input reactor with low cost silicon steel core to strengthen cost competitiveness of the manufacturer. The proposed control method controls input current every half cycle of the line frequency to get unit power factor and at the same time to reduce switching loss of devices and acoustic noise from reactor. This kind of converter is known as a Partial Switching Converter(PSC). In this study, theoretical analysis of the PSC has been performed using Matlab/Simulink while a 16-bit micro-processor based converter has been used to perform the experimental analysis. In the theoretical analysis, electrical circuit models and equations of the PSC are derived and simulated. In the experiments, micro-processor controls input current to keep the power factor above 0.95 by reducing the phase difference between input voltage and current and at the same time to maintain a reference DC-link voltage against voltage drop which depends on DC-link load. Therefore it becomes possible to comply with harmonic regulations while the power factor is maximized by optimizing the time of current flow through the input reactor for every half cycle of line frequency.

電磁反発式遮断器を搭載した超電導限流器とその大型化への検討

Using a high-temperature superconductor, we constructed and tested a model superconducting fault current limiter (SFCL). The superconductor and vacuum interrupter as the commutation switch were connected in parallel using a bypass coil. When the fault current flows in this equipment, the superconductor is quenched and the current is then transferred to the parallel coil due to the voltage drop in the superconductor. This large current in the parallel coil actuates the magnetic repulsion mechanism of the vacuum interrupter and the current in the superconductor is broken. Using this equipment, the current flow time in the superconductor can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of the parallel coil. In this paper, we describe the current limiting module using four serial and two parallel-connected YBCO thin films.

Study of Superconducting Fault Current Limiter Using Vacuum Interrupter Driven by Electromagnetic Repulsion Force for Commutating Switch

Using a high-temperature superconductor, we constructed and tested a model superconducting fault current limiter (SFCL). The superconductor and the vacuum interrupter as the commutation switch were connected in parallel using a bypass coil. When the fault current flows in this equipment, the superconductor is quenched and the current is transferred to the parallel coil because of the voltage drop in the superconductor. This large current in the parallel coil actuates the magnetic repulsion mechanism of the vacuum interrupter. Due to the opening of the vacuum interrupter, the current in the superconductor is broken. By using this equipment, the current flow time in the superconductor can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of the parallel coil

転流スイッチに電磁反発駆動真空遮断器を用いた超電導限流器の動作

Using conventional high-temperature superconducting wire, a model superconducting fault current limiter (SFCL) is made and tested. Solenoid coil using Bi2223 silver sheath wire is so made that inductance is as small as possible and a vacuum interrupter is connected in series to it. A conventional reactor coil is connected in parallel. When the fault current flows in this equipment, superconducting wire is quenched and current is transferred into the parallel coil because of voltage drop of superconducting wire. This large current in parallel coil actuates magnetic repulsion mechanism of vacuum interrupter. Due to opening of vacuum interrupter, the current in superconducting wire is broken. By using this equipment, current flow time in superconducting wire can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of parallel coil. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 52–61, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20315

Power Control of Domestic Microwave Ovens by Switching in the High-Voltage Circuitry

AbstractThe authors have developed a new power control method, in which a high-voltage switch is used, and the output power is controlled by changing the interval of half-wave current flow time in the secondary circuit of the transformer, The switch is actuated at zero-current (intermittent of half-wave current) by a controller and a phase-control device.With this method, there is no rush current, no electric arc and little magnetron filament temperature change, which results in the increased life of the magnetron.

点溶接機電極の先端部の温度上昇の実測と計算

The maximum temperature rise in electrode tip is estimated from the measured heat input to the electrode during one spot welding. It reaches as high as about 700°C for ordinary spot welding conditions of steel plates of 0.8-3.2 mm thickness.For calculation the electrode cross section is assumed constant along the electrode length, and the effect of wave form of heat flow from the tip is investigated. Q in Table 1 is the measured heat input to each side of the electrode per one welding under the conditions shown in the table. θ2 in the table shows the calculated results using the equation (9) under the following assumption, i.e. the heat flow wave form is taken as Fig. 11(a), heat flow time TH is assumed as equal to current flow time T0 shown in the table, the cross section of the electrode is taken as S2 corresponding to the root diameter of the electrode.Fig.14 shows the temperature distribution curves along the length when a constant heat H=1000 cal/cm2 sec flows in from the electrode tip for the duration TH=0.25, 0.5, 1.0, 1.5sec. Curves A-D show the temperature rise when the distance x0 of cooling end from the tip is infinity and A, B'-E' for x0=1 cm. For the calculation of the effect of cooling water, it is assumed that equation (33) holds, according to the model shown in Fig. 13 (h is taken as 1 for Fig. 14 and 18).Heat flow time TH is divided into two parts as shown in Fig.17 and the temperature at the moment C is calculated as the sum of the parts. Temperature due to the part AB is calculated using equation (49), T1 being time constant defined as in equation (43) and the period of BC is chosen far longer than time constant T2.It is easily shown that the magnitude of temperature fluctuation at a point I cm distant from the tip is negligible when intermittent heat input cycle is less than 1 sec/spot and we see that the cooling effect of cooling water is only effective to reduce the average temperature rise in the electrode under intermittent welding.Table 3 shows the temperature rise at the tip for cyclic heat flow from the tip for various combinations of x0, h, TH and Tw (i.e. cyclic period). The value shows the temperature at the moment C in Fig. 19 for H=1000 cal/cm2 sec.Fig.2, 4 shows the oscillogram of the temperature rise at 2 mm distant from the tip (Fig.1). Electrode pressure is also shown in Fig.2.

DISCUSSIONS ON “A THEORETICAL STUDY OF INDUCED ELECTRICAL POLARIZATION”

The analysis in the quoted paper is an attempt to calculate the induced polarization response of a two‐layer flat earth. The upper layer is a homogeneous overburden of thickness h with a resistivity [Formula: see text] and a dielectric constant of [Formula: see text]. The lower (semi‐infinite) medium which is the “aquifer” has a resistivity [Formula: see text] and dielectric constant [Formula: see text]. The value of the relaxation voltage as seen at the potential electrodes “immediately after” the current is shut off is designated Δϕ. The A’s of the above paper present a method for calculating the ratio Δϕ/V where V is the steady voltage across the potential electrodes during the time of current flow.

THE ELECTROLYTIC POLISHING OF AMPHOTERIC METALS

Experimental determinations of conditions necessary for the electrolytic polishing of amphoteric metals in alkali hydroxide solutions are described. The effects of temperature, electrolyte concentration, current density, and time of current flow are presented, as are differences among lithium, sodium, and potassium hydroxide solutions. Interpretation of the results in terms of a theory involving anodic polarizations has indicated the importance of the formation and maintenance of an anodic film whose electrical and mechanical properties determine critically the nature of the surface resulting from anodic treatment. Further applications of such studies toward the elucidation of mechanisms of anodic processes are indicated.

Spectro-Photoelectrical Effects in Argentite the Production of an Electromotive Force by Illumination

Electromotive force produced by illumination of argentite.---If argentite (${\mathrm{Ag}}_{2}$S) is connected in a closed circuit with a galvanometer and one surface of contact is illuminated, an e.m.f. is produced which increases with the intensity, reaching a limit of about.013 volt for 600 candle-meters and over. On continued exposure, marked fatigue is shown, the e.m.f. decreasing in a few minutes to half value. By use of a monochromatic illuminator and a suitable intensity control, the e.m.f. was found to show a sharp maximum for about 1\ensuremath{\mu}. The results were found independent of the contacts used whether Cu, Al, Fe, Sn, Ag or water. The effect is clearly not thermoelectric. Various samples showed similar results. No transmitted light effect was observed. Six other minerals showed the effect to a greater or less extent, including molybdenite (Mo${\mathrm{S}}_{2}$) and acanthite (${\mathrm{Ag}}_{2}$S).Resistance of argentite.---(1) Variation with voltage. The resistance, measured instantaneously was only half as great for 20 as for 4 volts. The resistance is about 4/5 as great in the light as in the dark, the ratio being independent of voltage. (2) Variation with time of current flow. The resistance increased with time, the crystal finally reaching a state when it was no longer light sensitive. Recovery was slow.