Arc Current Waveforms Research Articles

Electrostatic Discharge Plasma Propagation Speed on Solar Panel in Simulated Geosynchronous Environment

An international project has started to establish an International organization for standardization standard for the electrostatic discharge (ESD) on the solar array panel. For the ESD ground test of satellite solar panel, it is important to understand the characteristics of a primary arc discharge. A solar array coupon made of triple-junction cells is used to understand the primary arc characteristics. In particular, the experiment focuses on the measurement of the propagation speed of plasma generated by the primary arc. The plasma propagation is analyzed using images captured by a high-speed video camera and an image intensified camera. The plasma propagation speed derived from discharge images decreases in proportion to the inverse of the square root of time. The arc current waveform assuming the decreasing speed agreed with the experiment waveform very well.

A numerical study of the supply mode effects on high-pressure mercury discharge lamp dynamic thermal behavior

This paper presents a numerical study of the dynamic behavior of high-pressure mercury discharge lamp as a function of supply mode. Bidimensional time-dependent equations have been solved by using a semi-implicit finite-element code. The model has been developed in the frame of the local thermodynamic equilibrium hypothesis. After validation by using experimental data from the literature, this model was applied to analyze the effects of some key parameters such as frequency for an ac arc current and the ratio cycle parameter for square arc-current wave form on the convective process. The results obtained have been used to analyze the dynamic thermal behavior of high-pressure mercury plasma (pressure equal to 0.3 MPa) working under currents widely different in frequency and wave form.

On the Modeling of Long Arc in Still Air and Arc Resistance Calculation

An important macroscopic arc parameter, describing its complex nature is the arc resistance. It can be easily calculated by using the well-known Warrington formula. Authors investigated the results of Warrington's tests. By taking into account the conditions under which they are obtained (e.g., inaccurate measurement devices), it is unquestionable that these results are today highly empirical and not accurate and general enough. Laboratory testing provided in the high-power test laboratory FGH-Mannheim (Germany), in which long high current arcs are initiated, was the basis for the research results presented in the paper. Based on the analysis of laboratory-recorded arc voltage and current waveforms, the new arc model is derived. An example of arc computer simulation using the new model is given. Based on the new arc model, a new approach to arc resistance calculation is presented. The new formula for arc resistance is compared with the old Warrington formula.

Long arc in free air elongation effects modeling and simulation

AbstractIn the paper the elongation effects on the long arc in still air are investigated and modelled. Arc is initiated under laboratory conditions in the high power test laboratory FGH‐Mannheim (Germany). Based on the analysis of laboratory arc voltage and current wave forms, the new dynamic arc model, taking into account the arc length variation, is derived. An example of arc computer simulation using the new model is given. The main features of the simulated arc are presented. The main features of both the real and the simulated arc are given in the time and the spectral domains.

超狭開先ＧＭＡ溶接プロセスの開発 ４ 位相制御型ＧＭＡ溶接プロセスによる開先内でのアーク入熱分布制御

GMA welding process with synchronized control system consisting of a pulsed arc current waveform with cyclical variation of wire feed rate has been developed on the base of computer simulation. In the ultra-narrow gap (less than 5 mm gap) welding process, as the welding wire melting behavior is controlled by low frequency pulsated arc current waveform, the arc generating at the wire tip can be widely oscillated in the direction of thickness. The arc heat pole is dominated by wire melting tip position in consumable electrode welding process, and the arc heat distribution can be changed by this wire tip behavior. The wire melting tip position is represented by wire extension which is a function of wire feed rate and wire melting rate. In order to more-adequately control the arc heat distribution, this report describes synchronized control process between wire feed rate and pulse current waveform in the ultra-narrow gap GMA welding. The important control factor in the newly proposed process is phase shift θ between pulse current waveform and wire feed rate pattern. Firstly, the non-steady state simulation of the wire melting behavior is developed in the case that both arc current and wire feed rate change periodically with low frequency. From simulation results of wire tip behavior under various phase sifts and wire feed rates and pulse conditions, the adaptive welding conditions can be found effectively. Secondly, the synchronized control of welding was carried out under adaptive welding conditions. From the experimental results, it was verified that the arc heat distribution was effectively controlled with the phase shift method expected by numerical simulation thus adequate penetration shapes were obtained in the proposed welding process.

超狭開先ＧＭＡ溶接プロセスの開発 ３ シールドガス組成制御によるＧＭＡ溶接プロセスの開発

In previous reports, an ultra-narrow gap CO2 gas metal arc welding process has been developed in order to produce excellent welded joints. In the ultra-narrow gap (less than 5 mm gap) welding process, as the welding wire melting behavior was controlled by low frequency pulsated arc current waveform, the arc generating at the wire tip was widely oscillated in the direction of thickness and a good weld bead with large throat thickness was formed. In such a higher efficient welding process, the strong arc force of CO2 arc is essential to obtain sound beads without lack of fusion at a groove bottom, however, the oxygen content of weld metal in CO2 arc welding has to be reduced to obtain high-toughness at weld metal. In this report, a newly welding process is proposed in which an arc is widely oscillated along groove walls and oxygen content of welded metal is reduced as periodically controlling composition of CO2 gas in shielding gas. As an arc length between the wire tip and groove wall is held constant in ultra-narrow I type gap joint, arc current at stable operating point of CO2 arc essentially decreases less than that at stable operating point of Ar arc in constant potential characteristics of power source. It was confirmed from the numerical simulations on both wire melting and electric welding circuit that pulsated current waveform was produced as periodically alternating CO2 arc with MIG arc. Using the developed welding torch locally introducing CO2 gas into Ar+2%O2 shielding gas, the welding was carried out under V-type groove with less than 30 degree in the bevel angle. It was shown that the arc was widely oscillated along V groove walls and sound bead was formed in one side welding. Furthermore, it was confirmed that the oxygen content of weld metal in the proposed process was reduced to the level of that in MIG arc welding, and absorbed energy of weld metal was the same level as the MIG arc welding.

Ultranarrow GMAW process with newly developed wire melting control system

An ultranarrow gap GMA welding (UNGW) process with less than 5 mm gap width has been developed in which the arc pole is strongly oscillated over the groove wall in the thickness direction. A simulation model for wire melting tip behaviour with dc pulse current has been proposed and verified by observation of the tip motion in the UNGW groove. This simulation can define the optimum welding conditions to avoid welding defects. A synchronised control system consisting of a pulsed arc current waveform with cyclical variation of wire feed rate has been successfully developed on the base of the computer simulation. The newly developed UNGW system makes it possible to reduce arc heat input density sufficiently to produce an excellent weld joint with a narrow (1–2 mm) HAZ. Penetration shape control can also be achieved by this control method.

Ultranarrow GMAW process with newly developed wire melting control system

An ultranarrow gap GMA welding (UNGW) process with less than 5 mm gap width has been developed in which the arc pole is strongly oscillated over the groove wall in the thickness direction. A simulation model for wire melting tip behaviour with dc pulse current has been proposed and verified by observation of the tip motion in the UNGW groove. This simulation can define the optimum welding conditions to avoid welding defects. A synchronised control system consisting of a pulsed arc current waveform with cyclical variation of wire feed rate has been successfully developed on the base of the computer simulation. The newly developed UNGW system makes it possible to reduce arc heat input density sufficiently to produce an excellent weld joint with a narrow (1–2 mm) HAZ. Penetration shape control can also be achieved by this control method.

A new approach to arc resistance calculation

An important macroscopic arc parameter, describing its complex nature is arc resistance. As known, the fault arc resistance can be calculated by the Warrington formula. The authors investigated the results of Warrington's tests. Warrington derived a relation for the arc voltage by using the measured arc voltage gradient and arc current as input data. By analyzing these measurements and by taking into account the conditions under which they are obtained (inaccurate measurement devices), it is unquestionable that the results are highly empirical and not accurate and general enough. Laboratory testing, provided in the high power test laboratory FGH-Mannheim (Germany), in which long high current arcs are initiated, was the base for the research results presented. In this paper a new approach to arc resistance calculation is given. Two independent approaches delivered the same equation. Both approaches are based on a suitable and a simple arc model assuming the rectangular wave form of the arc voltage, which is in phase with the arc current wave form. The new formula for arc resistance is compared with the Warrington formula. The influences of arc elongation are also investigated.

New dynamic model, laboratory testing and features of long arc in free air

In this paper the long arc in free air is investigated. First, arc is initiated under laboratory conditions in the high power test laboratory FGH-Mannheim (Germany). Based on the laboratory obtained data records, the main features of arc are derived. By this arc, voltage and current are processed. An important feature of arc, the variation of arc length, is analyzed. Based on the analysis of arc voltage and current wave forms, the new dynamic arc model, taking into account the arc length variation, is derived. Arc is modeled as a current dependent voltage source with the characteristic distorted rectangular waveform and arc length dependent amplitude. Arc is considered as a source of higher harmonics distorting by this other signals in the network. An example of arc computer simulation using the new model is given. The main features of simulated arc are presented, too. Features of both the real and the simulated arc are given in the time and the spectral domains.

A method of making an equivalent circuit for breaking arc

AbstractThis paper considers breaking of the dc circuit by electrical contact and describes a method for measuring the voltage and current waveforms of the breaking arc and surge, as well as a method for deriving the arc equivalent circuit in the latter period of the breaking arc. The small inductance of the whole simulating circuit as well as the equivalent capacitance of the electrical contacts are determined so that the observed voltage waveform induced in the text circuit during the surge (i.e., the induced voltage waveform after chopping) and the voltage value in the resistor calculated in the simulating circuit agree.Next, the equivalent arc resistance, coherence, and the phase angle are calculated from the voltage and current waveforms of the breaking arc, which contain the high‐frequency components. Using the equivalent capacitance, equivalent arc resistance and phase angle, the arc equivalent circuit is estimated that can simulate the measured arc voltage and current waveforms. It is seen as a result that the arc equivalent circuit in the latter discharge period of the breaking arc can be represented as a series‐parallel circuit where resistor ra1 is connected to the parallel circuit (ra2/Ca) of resistor ra2 and the equivalent capacitance Ca. When, for example, the Ag electrical contact on a relay breaks the circuit of dc 36‐V and a noninductive resistor 3 ω, the arc equivalent circuit in the 105 ∼ 106 band in the latter period of the breaking arc is constructed by ra1 = 65 ω, ra2 = −68 ω, and Ca = 200 pF.

Macroparticle Dynamics during Multi-Cathode-Spot Vacuum Arcs

Macroparticle dynamics in multi-cathode-spot (MCS) vacuum arcs were studied by utilizing laser Doppler anemometry (LDA) methods for in situ measurement of the cathodic macroparticle velocities and relative emission rates. Arc current pulses having peak values of 1-2 kA at either 6 or 1 ms after arc initiation were investigated. Systematic dependence of the macroparticle dynamics (i.e., speed and direction of flight) on cathodic thermophysical properties, location of the measurement probe in the interelectrode region, instantaneous value of the arc current, arc current waveform, and macroparticle size was determined. It was found that the macroparticle velocity increased with the melting temperature of the cathode metal, distance from the cathode surface, and the instantaneous value of the arc current, and decreased with macroparticle size and the rise time of the current waveform. All the above dependencies may be understood as direct indications of the plasma-macroparticle interaction during the discharge. The measured instantaneous relative emission rates were found to peak later than the arc current but before the peak average cathode surface temperature, which was estimated using a semi-empirical model. This result may be an indication of the dependence of cathodic erosion in the form of molten metal droplets on the average cathode surface temperature.

Laser Doppler anemometry: a tool for studying macroparticle dynamics in a vacuum arc

A method, based on laser Doppler techniques, for measuring macroparticle velocities and emission rates in vacuum (metal vapour) arcs is presented. A real-fringe forward-scattering system was employed, excited by a He-Ne laser, producing an ellipsoidal probe volume. Time domain analysis of individual scattering events was used to determine the macroparticle velocity components, while counting of the individual events was used to yield macroparticle emission rates. The experimental method enabled a study of macroparticle dynamics as a function of space and time in pulsed vacuum arcs of 1 and 2 kA peak current, 5 and 30 m s-1 duration, sustained between 12-14 mm electrodes, spaced 4 mm apart and fabricated from either Cd, Zn, Al, Cu, or Mo. Broad velocity component distributions, ranging from about 10 m s-1 up to about 800 m s-1, and dependent on cathode metal, arc current waveform, time after arc initiation and spatial location in the discharge volume, were measured. The macroparticle emission rate was found to reach its peak a few milliseconds after the occurrence of peak current.

交流熔接電弧の安定度と熔接機特性との関係について

The a. c. welder with high efficiency due to the small stray load loss is also preferable in the standpoint of arc stability. The instantenuous value of the leakage flux of the transfcrmer is not zero at the instant of the zero value of the welding current due to the m. m. f. of the eddy current induced by the flux, so the secondary open voltage does not rises to its steady value in gtantenucusly by the damping action of the leakage flux above mentioned. The voltage recovery at open circuit due to arc vanishing lags only about 1/2000 second by a new designed welder which has a efficiency value of 88%, the time being appr-oximately one third of a old type welder, whose efficiency value is 70%. The difference of the arc stability of the above mentioned two welders is observable clearly by hand welding when we use some electrodes, but is not observable when we use some other electrodes.The arc voltage and current wave forms by a electrode of peer arc stability are shown in Fig.9, (a) and (b) being the case of the welder of quick and slow voltage recovery respectively. By a electrode of good arc stability, the arc voltage rises slowly after zero currnt intant (Fig.1), due to the good conduc tivity of the arc part, so the lagging of the voltage recovery of the welder does not affect on the arc stability.