Arc Control Research Articles

Protection of insulator strings against high-power Arcs

Arcs with high current amplitudes and long duration can cause severe damage or destruction of insulator strings installed in overhead lines or substations. This paper describes the effects to be expected and the range of thermal loads which include a risk if no arcing protective fittings are used. Furthermore, it describes the requirements which arcing protective fittings must meet, the forces which act on the arc, and how the excess pressure inside the plasma channel of the arc shaft can be used for an effective control of the arc.

Numerical Simulation of a Moving High-Current Vacuum Arc Driven by a Transverse Magnetic Field (TMF)

This paper deals with the numerical simulation of the constricted high-current vacuum arc (>15 kA), driven by a transverse magnetic field (TMF), as found in vacuum circuit breakers applying the TMF arc control. The magnetohydrodynamic approach, together with the detailed heat transfer and evaporation equations for the electrodes, is used to describe the arc behavior self-consistently, restricted to 2-D. A newly developed model describes the cathode attachment of the constricted arc, as a large laterally extended foot points, instead of regular cathode spots. The arc maintains itself when the electrode temperatures are higher than 3400 K on the cathode and 2900 K on the anode. This model leads to the characterization of the physical quantities of the arc plasma and describes the arc motion. A stepwise movement of the arc results due to different instantaneous velocities of the current attachment areas at the cathode and anode.

Development of High-Voltage Vacuum Circuit Breakers in China

This paper introduces research work on the development of high-voltage (HV) vacuum circuit breakers (VCBs) in China from its starting point in 1989 to 2006. In this period, a 126-kV two-breaks VCB prototype and a 126-kV single-break VCB prototype were developed. A latest 252-kV single-break interrupter prototype is introduced. Five HV VCBs technologies are discussed, which include HV vacuum insulation, high current interrupting technology with long contact gaps, increasing nominal current, operating mechanism characteristics, and contact bouncing damping. In vacuum insulation, adding a metal ring at the electrode back can decrease breakdown possibilities in the gap between the electrode back and the main shield. A surface melting layer of contact material could have an influence on voltage withstanding capability of a vacuum gap. For interrupting high current with long contact gaps, a strong axial magnetic field (AMF) is needed for better vacuum arc control. Therefore, a single coil AMF electrode is introduced. Heat radiators are effective to increase the nominal current of VCBs. Thermal analysis can help to give appropriate design parameters. There is an optimum opening characteristic that is helpful to improve the interrupting performance of VCBs. Permanent magnet operating mechanism and spring-type operating mechanism are suitable for HV VCBs. Contact bouncing in HV VCBs can be damped by installing contact spring and bellows on the stationary end of VCBs.

연면 트래킹에 의한 탄화 거동

본 논문에서 전극 간 표면누설에 의한 탄화도전로의 형성과 방향성에 대해 연구하였다. 표변에서 트래킹의 특성은 노출된 충전부사이에서 절연 파괴되었다. 고속카메라시스템을 이용하여 전극 간 방전과 지락, on/off 서어지에서 발생되는 아크성장 메커니즘을 촬영하고, 결과를 분석하였다. 향후 아크제어를 동한 에너지 이용기술의 적용이 기대된다. In this paper, we are studied on the direction and formation of carbonized conductive path according to surface leakage current between electrodes. The characteristics of the tracking as surface is broken down between exposed live parts. Using the HSIS(high speed imaging system, 100,000[fps], redlake ltd., USA), it took photographs by arc growth mechanism occurred in on/off surge, ground fault and discharge between electrodes. Then the results was analyzed. Hereafter, it expected effects that application of energy utility technology through the arc control.

New technological trends in high-voltage power circuit breakers

This article introduces a comprehensive survey on new trends in high-voltage (HV) power circuit breakers (CBs) technology. Applying the new puffer and the self-blast technologies, the ratings of SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> CBs have reached upto 1,100 kV, 80 kA, and 50 GVA, which is the world's largest gas insulated switchgear (GIS), with independent pole operation and utilizing the advantages of external composite insulators. Several new vacuum arc control technologies are discussed. New generations of controlled intelligent switching devices that implement new power electronic actuating devices are introduced. Finally, superconducting fault current limiters (SFCLs) are introduced. SFCLs have two main properties: current limitation capability and ultra high-speed operation. SFCLS could be a key technology for future power systems engineering

Advanced Power Supplies designed for Plasma Deposition and Etching

AbstractPlasma deposition and etching processes are used for a wide range of applications as for example the production of semiconductor circuits, flat panel displays, solar cells, architectural glass and data storage media. To fulfill the special needs of each single process stable DC, MF and RF process power ranging from 50W to 200kW is needed.All generators need a high precision process control and a supreme arc management with adaptable parameters to provide minimal disturbances in the plasma process and to obtain optimized results in terms of film quality, homogeneity and uniformity over the whole substrate. The fast and flexible arc handling leads to an improvement in the film quality by minimizing flaws and defects and enables the use of very high sputter rates.To fit DC process demands a new concept for a modular DC system has been realized where up to four 30kW modules can be combined using master slave concept. The arc management and control of the DC module has an intelligent control enabling arc detection times of less than 1μs and a residual energy delivered to the process of only 6 mJ per kW.For MF processes a fast and effective arc management is an even more important tool for keeping reactive processes stable. The new generation of MF power supplies enables arc detection and shut off times of 5μs with a residual energy delivered to the process of only 5 mJ per kilowatt. This yields the additional advantage that even when the cathode material is almost used up and consequently the arc probability increases, the low residual energy values contribute to an extended service life of the cathode and to better utilization of the target material.Essentially, the outstanding feature of effective arc management is an undisturbed plasma during the whole operation time. The fast arc suppression minimizes the interruption in the sputtering process to negligibly small values. However, because arcs also serve to remove unwanted materials on the cathode, power supplies must be able to control and regulate the arc energy precisely. MF power supplies are available for process power up to 200kW.RF systems are based on two different concepts to fit the broad power range between 50W and 50kW. For the low energy range a fully transistorized and μC‐controlled RF generator was developed. This generator has been designed for a max. power of 3kW. Important features are the compact size, robustness, reliability and easy maintenanceTo have a cost effective design for a high power RF generator in this power range an oscillator ‐ amplifier concept has been chosen with a solid state driver in combination with a tube type end stage amplifier.To fit todays demands for advanced etching a dual frequency system consisting of a 13.6 MHz and a 3.4 MHz unit was developed. This enables the possibility to separately control plasma density and ion energy of the discharge.

Thermal and metal transfer behaviours in pulsed current gas metal arc weld deposition of Al–Mg alloy

The control of pulsed current gas metal arc (GMA) welding is highly critical owing to the simultaneous influence of the pulse parameters on thermal and metal transfer behaviours of the process. An analytical model has been developed to provide a theoretical understanding of the influence of pulse parameters on the behaviour of metal transfer and thermal characteristics in pulsed current GMA welding using Al–Mg filler wire. The variations in thermal and metal transfer behaviours with changes in pulse parameters have been satisfactorily analysed considering a summarised influence of pulse parameters defined by a dimensionless factor &phis; = (Ib/Ip)ftb, proposed previously. A large number of process parameters have been considered, as a result of using four different GMA welding power sources. The hypothesis has been verified using some previously reported experimental results. The theoretical model may be useful in the control of pulse parameters to achieve desired behaviours of thermal and metal transfer under different conditions of weld fabrication, thereby facilitating more universal application of GMA welding.

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.

Magnetic control of high current vacuum arcs with the aid of an axial magnetic field: a review

This paper reviews the most important topics related to the control of high current vacuum arc with the aid of axial magnetic field (AMF); the main experimental findings, explanations, and theories and the effect of AMF nonuniformity. The state of the art AMF contact systems for commercial vacuum interrupters are also presented.

Physics of high-current interruption of vacuum circuit breakers

The present state of knowledge concerning the physical phenomena of high-current interruption with vacuum interrupters (VI) is reviewed. Two arc control methods, application of externally applied axial magnetic field (AMF) or transverse magnetic field (TMF), are available to distribute the heat flux from arc to contacts homogeneously over contact surface, to avoid local overheating. AMF spreads the arc at fixed location. TMF moves the constricted arc over contact surface. Change from diffuse to constricted arcing mode results from superposition of two effects: instability of anode sheath and influence of magneto-gas-dynamic, when no AMF component exists. Conditions of arc memory at current zero determine the process of current extinction and of recovery of breakdown strength to its ultimate value. Evaporation of metal vapor continues. Charge exchange between fast ions and slow vapor atoms increases the residual charge, left in the switching gap at current zero. Post arc current prolongs and increases consequently. Breakdown during recovery of dielectric strength occurs instantaneously or sporadically delayed. Behavior of breakdown is essentially determined by vapor density. Breakdown mechanism of delayed breakdown is still unresolved. Vapor density is too low to initiate breakdown alone. Lack of fundamental knowledge in combination with complexity hampers numerical treatment of arc behavior, as well as heat flux to contact during arcing and process of interruption presently, as needed for interpretation of experimental results and prediction purposes.

Advanced generation of rotatable magnetron technology for high performance reactive sputtering

Magnetron performance is ultimately the determining factor in the productivity of glass sputter coating technology. Maximum power density, target utilization and efficiency, coating uniformity, material deposition rates, vacuum reliability, arc and debris control, quick turn-around and ease of maintenance all contribute to the overall efficiency of any magnetron sputter source. The state of the art in magnetron sputter deposition is now based upon reactive sputtering of rotatable cylindrical magnetrons using AC power supplies. A new generation of rotatable sputter magnetrons is based upon design from first principles for optimized use with high current mid-frequency AC sputtering power supplies. Improved target designs result in more robust vacuum sealing and greater than 90% material utilization. Improved magnet fixtures and process control results in stable, high deposition rates for reactive sputtering with 3% uniformity range. Results from lifetime testing and production systems are presented. Critical performance features including current handling capability, seal lifetime, and process uniformity are discussed.

Characterisation of an indirectly heated cathode source using Langmuir probe diagnostics

There is a growing diversity of beam requirements for ion implantation. This is mirrored by widely different chemical and physical properties of the materials necessary for the generation of ion beams. Optimum operating conditions for any specific ion species are difficult to determine and it is crucial to obtain a better understanding of the roles of the physical configuration of the arc chamber and arc control parameters for the different species of interest.The relationships between the electron temperature and arc control parameters were investigated for argon and BF3. The spatial distributions of electrons and ions were also studied using probes located in different positions in the arc. For the two species studied, the electron temperatures for similar arc conditions were found to be different and the nature of the dependence of this temperature on operating conditions was also found to be different.

Langmuir probe analysis of a BF3 discharge in a high current ion source

Optimisation and performance of an ion source demands an intimate knowledge of the role of gas and surface phase processes in the cracking of the precursor molecule. To this end, it is necessary to understand the characteristics of the source plasma and the role of physical configurations of the arc chamber and arc control parameters. In BF3 plasmas, there is clear evidence that high energy electrons play a significant role in the production of B+ ions. Therefore, the plasma conditions which optimise the production of the species of interest (BF2+ and B+) have been studied using a symmetrical, floating double Langmuir probe arrangement that inherently lends itself to the study of the characteristics of the high energy electrons, with minimal perturbation of the plasma. In this paper, the electron temperature dependence on the source control parameters are the main areas investigated. The electron temperatures measured for two different source configurations are also compared. The dependence of electron temperature on different operating conditions is found to be different. The electron temperature is found not to be uniform across the arc chamber.

Development of High Interruption Capability Vacuum Circuit Breaker-Technology of Vacuum Arc Control-

Vacuum circuit breakers (VCB) have been widely used for power distribution systems. Vacuum Interrupters, which are the current interruption unit, have been increased its interruption capability with the development of vacuum arc control technology by magnetic field. There are three major type electrodes: disk shaped electrodes, radial magnetic field electrodes, axial magnetic field (AMF) electrodes. In the disk shaped electrode, the vacuum arc between the electrodes is not controlled. In the AMF electrode, the vacuum arc is diffused and stabilized by an axial magnetic field, which is parallel to the arc current. In the last type of electrodes, the vacuum arc column is rotated by magnetic force generated by the current flowing in the electrodes. The interruption current and the voltage of one break VCB is increased to 100 kA, 144 kV respectively. This paper describes basic configurations and functions of VCB, vacuum arc control technology in vacuum interrupters, recent researches and applications of VCB.

High-current arc hazards in the ITER-like magnet system

An analysis of expected arc parameters has been carried out for possible short-circuit accident in the magnet system of a large tokamak like International Thermonuclear Experimental Reactor (ITER). Based on a wide review of arc application in the various technical devices, the relationships for arc parameters are found to be extended to the ITER conditions. The arc welding devices, arc-plasma torches, arc heaters of gas, arc furnaces, arc control devices and arc switches have been considered. The low-pressure, high-pressure and vacuum arcs have been considered. The arc voltage drop at the various ITER conditions can be evaluated on the basis of presented equations. The approximations by these formulae give a maximum arc power in the range of 50–100 MW for an emergency arc current of 140 kA and arc length of 12 cm.

Influence of photopolymerization light source on enamel shear bond strength after bleaching

This study evaluated the influence of 3 different photopolymerization sources on enamel shear bond strength after bleaching with 10% carbamide peroxide. Seventy-two incisive bovine teeth were randomly divided into 6 groups (n=12) according to bleaching treatment and photopolymerization source used: G1 -- Bleached / Halogen lamp; G2 -- Not bleached / Halogen lamp (control); G3 -- Bleached / Light-emitting diodes (LED); G4 -- Not bleached / Light-emitting diodes (LED) (control); G5 -- Bleached / Xenon plasma arc; G6 -- Not bleached / Xenon plasma arc (control). Experimental groups were exposed to bleaching agent for a period of 14 days, with a daily contact of 4 h and then stored in artificial saliva at 37 degrees C. Control groups were stored in artificial saliva at 37 degrees C for same period of bleaching treatment. Procedures for bonding composite resin to enamel were carried out according to manufacturer instructions. After storage in distilled water at 37 degrees C for 24 hours, all samples were submitted to shear bond strength test. G2 had the highest mean value (14.86 MPa) while G5 had the lowest (12.32 MPa). The comparison of groups by 2-way ANOVA showed that there were no significant differences for either of the factors considered in this study (bleaching and photopolymerization source), hence the interaction between these factors. It was therefore possible to conclude that neither enamel bleaching nor the photopolymerization source used had any influence on enamel shear bond strength.

High-speed DCEN TIG welding of very thin aluminium sheets with magnetic arc control

High-speed DCEN TIG welding of very thin aluminium sheets with magnetic arc control

Classification of Local Optimal Syntheses for Time Minimal Control Problem with State Constraints

This paper describes the analysis under generic assumptions of the small time minimal syntheses for single input affine control systems in dimension 3, submitted to state constraints. We use geometric methods to evaluate the small time reachable set and necessary optimality conditions. Our work is motivated by the optimal control of the atmospheric arc for the re-entry of a space shuttle, where the vehicle is subject to constraints on the thermal flux and on the normal acceleration

In vitro evaluation of long-term bonding of Procera AllCeram alumina restorations with a modified resin luting agent

Statement of Problem. Bonded densely sintered aluminum oxide ceramic restorations such as Procera AllCeram laminates rely on a strong and long-term durable resin bond. Air particle abrasion and a phosphate-modified resin luting agent have the potential to provide such bonds to aluminum oxide ceramics, but their efficacy on the Procera AllCeram intaglio surface is unknown. The inherent microroughness of this surface may influence bond strengths, because micromechanical interlocking is a main contributor for adhesion of resins to ceramic materials. Purpose. This study evaluated the bond strength of a phosphate-modified resin luting agent with and without silanization to an air particle-abraded Procera AllCeram intaglio surface compared with a conventional resin-bonding system before and after artificial aging. Material and Methods. Sixty square (10 × 10 × 2 mm) specimens of Procera AllCeram alumina ceramic with the Procera intaglio surface were air particle abraded with aluminum oxide. Composite cylinders (2.9 mm in diameter and 3.0 mm in width) were fabricated with Z-250 composite and bonded to the ceramic specimens with either Panavia 21 TC or Rely X ARC (control) and their corresponding bonding/silane coupling agents. In addition, Panavia was used without silanization as suggested in similar studies. Subgroups of 10 specimens were stored in distilled water for either 3 or 180 days before shear bond strength was tested with a universal testing machine (MPa) until fracture. The 180-day specimens were subjected to thermocycling at 2000 cycles every 30 days (12,000 cycles total). Data were analyzed with 1-way analysis of variance and Tukey's multiple comparison (α=.05). Failure modes were examined with a light microscope (original magnification × 25). Results. Differences between short-term and long-term groups were highly significant (P=.000). Bond strength with Rely X ARC and its silane coupling agent (22.75 ± 4 MPa) decreased significantly (P=.000) after artificial aging (3.32 ± 3.62 MPa). Panavia 21 after silanization revealed significantly different (P=.003) early (21.42 ± 4.3 MPa) and late (16.09 ± 2.37 MPa) bond strengths but achieved the highest bond strength after artificial aging. Bond strengths of Panavia without silanization both early (8.06 ± 2.1 MPa) and late (6.91 ± 2.49 MPa) were not significantly different. Failure modes were mainly adhesive at the ceramic surface for all groups. Conclusion. Panavia 21 in combination with its corresponding bonding/silane coupling agent can achieve an acceptable resin bond to the air particle-abraded intaglio surface of Procera AllCeram restorations after artificial aging, which had mixed effects on the other investigated groups. The conventional resin luting agent revealed the most dramatic decrease in bond strength. (J Prosthet Dent 2003;89:381-7.)

Optimal Control with State Constraints and the Space Shuttle Re-entry Problem

In this article, we initialize the analysis under generic assumptions of the small time optimal synthesis for single input systems with state constraints. We use geometric methods to evaluate the small time reachable set and necessary optimality conditions. Our work is motivated by the optimal control of the atmospheric arc for the re-entry of a space shuttle, where the vehicle is subject to constraints on the thermal flux and on the normal acceleration. A multiple shooting technique is finally applied to the computation of the optimal longitudinal arc.