Arc Root Movement Research Articles

Influence of a transverse magnetic field on arc root movements in a dc plasma torch: Diamagnetic effect of arc column

The effect of a transverse magnetic field on the anodic arc root movement inside a dc plasma torch has been investigated. The arc voltage fluctuation, which represents the degree of the arc instability, was reduced to 28.6% of the original value and the high frequency components in the voltage signal also decreased in their magnitudes. The inherent arc instability in a dc thermal plasma torch seems to be suppressed by a diamagnetic effect of the arc column. Furthermore, the measured voltage wave forms indicated that the arc root attachment mode would be controllable by a transverse magnetic field.

Arc Root Motions in an Argon–Hydrogen Direct-Current Plasma Torch at Reduced Pressure

Arc root motions in generating dc argon-hydrogen plasma as reduced pressure are optically observed using a high-spped video camera. The time resolved angular position of the arc root attachment point is measured and analysed. The arc root movement is characterized as a chaotic and jumping motion along the direction on the anode surface.

Arc Root Motion in an Argon-Hydrogen DC Plasma Torch

Arc root motion on the anode surface of a DC nontransferred plasma torch was observed. Adding hydrogen changes the arc root attachment from a diffused type to a constricted type, and the arc root of Ar-H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> plasma suddenly jumps from one spot to another irregularly. Images of the arc root motions taken by a high-speed video camera are presented.

Arc Voltage Fluctuation in DC Laminar and Turbulent Plasma Jets Generation

Arc voltage fluctuations in a direct current (DC) non-transferred arc plasma generator are experimentally studied, in generating a jet in the laminar, transitional and turbulent regimes. The study is with a view toward elucidating the mechanism of the fluctuations and their relationship with the generating parameters, arc root movement and flow regimes. Results indicate that the existence of a 300 Hz alternating current (AC) component in the power supply ripples does not cause the transition of the laminar plasma jet into a turbulent state. There exists a high frequency fluctuation at 4 kHz in the turbulent jet regime. It may be related to the rapid movement of the anode attachment point of the arc.

Arc root mobility on piezoelectrically actuated contacts in miniature circuit breakers

A novel contact opening mechanism has been developed using a piezoelectric actuator to open the contacts in a low contact opening velocity circuit breaker. The arc control on the contacts is critical for successful current interruption (10/sup 3/-10/sup 4/ A) in low voltage (<250V) devices. Previous work has shown how arc root commutation from the contact region into the arc chamber is affected by arc chamber materials, contact materials and the gap behind the moving contact for contact velocities between 1ms/sup -1/ and 10ms/sup -1/. This work is extended using a commercially available piezoelectric actuator to open the contacts. Contact opening speeds are assessed and the arc root mobility is characterized under this operating regime. A flexible test apparatus and solid-state high-speed arc imaging system are used to gather data on the arc root during the opening of the contacts. New experimental results are presented on the anode and cathode root velocity and arc root motion in an arc chamber with piezoelectrically actuated contact opening. These results can be used to improve the design of high current low voltage circuit breakers suitable for piezoelectric actuation.

Generation of long, laminar plasma jets at atmospheric pressure and effects of flow turbulence

Long, laminar plasma jets at atmospheric pressure of pure argon and a mixture of argon and nitrogen with jet length up to 45 fi,Hes its diameter could be generated with a DC are torch by! restricting the movement of arc root in the torch channel. Effects of torch structure, gas feeding, and characteristics of power supply on the length of plasma jets were experimentally examined. Plasma jets of considerable length and excellent stability could be obtained by regulating the generating parameters, including are channel geometry gas flow I ate, and feeding methods, etc. Influence of flow turbulence at the torch,nozzle exit on the temperature distribution of plasma jets was numerically simulated. The analysis indicated that laminar flow plasma with very low initial turbulent kinetic energy will produce a long jet, with low axial temperature gradient. This kind of long laminar plasma jet could greatly improve the controllability for materials processing, compared with a short turbulent are let.

Arc root commutation from moving contacts in low voltage devices

This paper focus on the arc commutation from a moving contact and in particular on the anode motion of a high current arc in low voltage current limiting circuit breakers. Recent investigations have observed that the anode arc root motion is affected by arc chamber geometry. It was previously assumed that cathode root motion was the dominant process. The study uses a flexible test apparatus with a solid state high speed imaging system. The experimental results presented show the influence of arc chamber venting, current level, current polarity and contact velocity on arc motion, Particular emphasis is made on the anode motion. The physical processes occurring in the anode root are discussed and related to the observed motion. The results show that the anode root is retarded at the tip of the moving contact and that this is primarily related to the venting process in the arc chamber.

Arc root dynamics in high power plasma torches — Evidence of chaotic behavior

Although plasma torches have been commercially available for about 50 years, areas such as plasma gun design, process efficiency, reproducibility, plasma stability, torch lives etc. have remained mostly unattended. Recent torch developments have been focusing on the basic understanding of the plasma column and its dynamics inside the plasma torch, the interaction of plasma jet and the powders, the interaction of the plasma jet with surroundings and the impingement of the jet on the substrate. Two of the major causes of erratic and poor performance of a variety of thermal plasma processes are currently identified as the fluctuations arising out of the arc root movement on the electrodes inside the plasma torch and the fluid dynamic instabilities arising out of entrainment of the air into the plasma jet. This paper reviews the current state of understanding of these fluctuations as well as the dynamics of arc root movement in plasma torches. The work done at the author’s laboratory on studying the fluctuations in arc voltage, arc current, acoustic emissions and optical emissions are also presented. These fluctuations are observed to be chaotic and interrelated. Real time monitoring and controlling the arc instabilities through chaos characterization parameters can greatly contribute to the understanding of electrode erosion as well as improvement of plasma torch lifetime.

Determination of plasma velocity from light fluctuations in a dc plasma torch

The fluctuations generated by arc root motion have been used to determine the velocity in a plasma jet. The phase angle relations resulting from time variations of light intensity profiles taken simultaneously across different sections of the plasma have been used to determine the velocity for different operating conditions of the dc torch. The experimental results have been compared with the theoretical predictions of a 2D MHD model of the dc plasma torch. The experimental and theoretical values appear to agree with a maximum deviation in the 5-10% range.

Experimental evidence of chaotic behavior in atmospheric pressure arc discharge

In free burning as well as in stabilized arc columns, the inherent movement of arc root results in fluctuation in arc voltage. A full knowledge and control over the arc root dynamics can effectively lengthen the life time, drastically improve performance and reliability in arc plasma devices. In this paper, we experimentally investigate the fluctuating voltage signals generated from an atmospheric pressure arc discharge produced in a hollow electrode plasma torch. For the first time, analysis of these signals reveal them to exhibit chaotic behavior. The present analysis is supported with real time behavior, phase portraits, power spectra and Lyapunov exponents. Dependence of system behavior on various control parameters is also investigated. This approach is interesting in the sense that it can lead to better understanding of physics for future researches on arc plasma jets and related devices.

Correction to "Anode and cathode arc root movement during contact opening at high current"

Correction to "Anode and cathode arc root movement during contact opening at high current"

Anode and cathode arc root movement during contact opening at high current

This paper presents experimental research into the behavior of short circuit break arcs ignited between opening contacts. The investigation is applied to arc chamber geometries commonly used in miniature circuit breakers (MCB). The movement of the anode and cathode roots are individually plotted from optical data, allowing the relative motion to be compared. The effect of a range of MCB configurations on the arc root motion has been investigated. The experiment was configured so that the fixed contact was always the cathode. The results show that the two are roots do not move away from the contact region simultaneously. Often the cathode root moved off the fixed contact and away from the contact region before the anode root commutated from the moving contact. The delay in anode root commutation leads to a delayed cathode root movement. These events are explained in terms of arc root emission processes.

Arc root mobility during contact opening at high current

This paper presents a test system, designed for the investigation of short circuit arcs related to miniature circuit breakers operating in a 240 V, AC supply. An optical fiber imaging system is used to identify arc root motion, with short circuit current up to 6 kA. Two methods are used to measure contact motion, a noncontact linear position sensor, and the optical fiber array. The optical fiber array uses software image processing to identify the position of the arc roots in the arc chamber. The identification of the arc roots allows for a study of the arc immobility at the initial stages of the event. Results are presented on variation of peak current level and arc runner materials on arc root motion for one geometry. The cathode root motion is shown to dominate the event.

Arc propagation over electrolytic surfaces under power frequency voltage

Flashover of wet polluted insulation is caused by the propagation of arcs along the electrolytic surface. Several factors affect this flashover process under actual operating conditions. These include the variation in pollution resistance due to arc root movement and thermal effects. The difference between the discharge gradient and the effective pollution gradient is an important factor in determining the growth of the discharge. Moreover, the distribution of instantaneous power along the wet surface also affect the arc propagation significantly. This paper describes the different physical criteria controlling are propagation, over electrolytic surfaces under ac voltage application. Contrary to the existing concept of a critical point, from where the discharge takes the final leap to complete flashover, the results obtained show that there are critical zones, referred to as the growth period lying between 40 to 63% of the total pollution length, which depends on the degree of surface pollution and the nature of pollutants.

Study of the dynamic and static behavior of de vortex plasma torches: Part II: Well-tye cathode

This work was devoted to the study of the dynamic and static behavior of de vortex plasma torch with a well-type cathode (power level below 100 kW). The dynamic behavior of the torch was characterized by the fulctuations of arc voltage and current, plasma jet radiation, and acoustic pressure. Characteristic frequencies of the arc root movement inside the torch were observed. By numerical simulation (with the numerical codeMelodie, it was shown that the position of the erosion diameter) of the axial velocity along the cathode channel near the wall. The static behavior of the torch was inverstigated for different cathode designs. The variations of voltage U with arc current I, gas flow rate G nature of the gas and cathode design were represented by semiempirical relationships established between dimensionless numbers. By dimensional analysis, the behavior of this torch was compared with that of two powerful torches: the Aerospatiale and the Plasma Energy Corporation torches.

Study of the arc root displacement and three-dimensional modelling of the thermal phenomena occurring in a hollow cathode submitted to an electric moving arc

In order to have a better understanding of the thermal processes occurring in an electrode submitted to a moving arc root, we have studied the displacement mode of cathode and anode arc roots. We have also elaborated a three-dimensional model able to solve the diffusion problem of the heat brought by the arc root to a hollow cathode of a plasma torch. This model takes into account the temperature dependence of the material properties (specific heat and thermal conductivity), the various phase changes occurring during the arc and the arc root motion.