High-current Vacuum Arc Research Articles

Model and simulation investigation of the whole process of high-current vacuum arc burning

With the development of the power industry and the increase in the capacity of power systems, vacuum switches have been developed rapidly. The distribution characteristics of the vacuum arc can reflect the working conditions of the vacuum switch. So, it is vital to understand the distribution characteristics in the vacuum arc burning process for understanding the interruption performance of vacuum switches. Based on the 3D magnetohydrodynamic model, we investigated the high-current vacuum arc burning process by modeling and numerical simulation. The research findings show a certain correspondence between the change in plasma parameters values and the change in arc current. The distribution of plasma parameters is uniform when the current is small. The distribution of plasma parameters in the first 1/4 cycle is more uniform than in the second 1/4 cycle. The evolution characteristics of the arc plasma parameters for interruption before the arc current maximum differ significantly from those for interruption after the arc current maximum and current maximum. The results of this study can provide a reference for the design and improvement of vacuum switches.

Experimental investigation on the erosion behavior in high-current vacuum arcs and resulting microparticles dynamics

Microparticles are an inevitable component of vacuum arcs. This paper focused on the dynamics of microparticle and erosion behavior in high-current vacuum arcs. The arc was sustained with AC 110 Hz between two butt CuCr alloy contacts with a diameter of 10 mm. An in situ microparticle diagnostic system suitable for vacuum arcs was developed. Three sources of microparticles were observed and the corresponding motion characteristics were obtained by our method. The influence of current and Cr content on erosion characteristics was investigated. The results indicate that the increase of Cr content contributes to inhibiting production of microparticles when the current is small. CuCr30 has the best effect of suppressing microparticle production among the three tested alloy materials under large current. The work of this paper helps with the understanding of microparticle behavior in high-current vacuum arcs and may provide a path for the design of a vacuum electrode.

Excitation Temperature Imaging of Vacuum Arc Based on Two-Line Radiance Method

The excitation temperature of the high-current vacuum arc was measured based on the intensity ratio of two Cu I spectra of 510.6 and 515.3 nm. Diffuse mode vacuum arcs with the peak current of 2 kA, igniting between 5-mm gap, 10-mm phi electrodes, Cu100, Cu80Cr20, and Cu50Cr50 wt.% contacts were measured by a multiple-imaging optical system and high-speed video camera. It turns out that the excitation temperature was almost evenly distributed in the gap. The excitation temperature at the current peak depended on the electrode material and took higher in the order of Cu100, Cu80Cr20, and Cu50Cr50. The excitation temperature was also measured by a spectroscopic approach, and it showed the same tendencies as the measurement using multiple-imaging optical systems and a high-speed video camera. The current decreasing phase of dc interruption was simulated by using semiconductor switches at the peak of ac 50-Hz current, and as a result, the current zero with a decreasing ratio of 30 A/μs was realized. The excitation temperature for the Cu100 electrode decreased with the decreasing current, whereas those for Cu80Cr20 and Cu50Cr50 increased. This difference suggests that developing direct current vacuum circuit breakers needs the optimization of the electrode materials, current waveform, and plasma parameters in the gap.

Numerical investigation on the influence of metal particles on the characteristics of a high-current vacuum arc

In the arc-burning process of a high-current vacuum arc (HCVA), the metal particles (MPs) splashed from the active anode will have a significant influence on the plasma characteristics of the arc column. In this paper, the influence of varying MPs on the characteristics of HCVA are studied by establishing a HCVA model containing single or multiple MPs. The simulation results show that when the MPs vaporized metal vapor (MV) enters the interelectrode region and once the arc column plasma cannot ionize all atoms immediately, the ionization layer and the neutral atom vapor area (NAVA) will be formed in the adjacent region of the MPs. When the MP diameter and temperature increase, the number of vaporized metal atoms increases, so that the influence range of MV increases, and the area of ionization layer and the NAVA increases. In addition, when the arc current increases or the MPs are closer to the cathode surface, the greater the ion number density and ion pressure around the MPs are, the stronger the compression on the MV will be, resulting in the decrease of the area of ionization layer and the neutral atom vapor, and the increase of the net ionization rate of the ion number density. When multiple MPs exist in the interelectrode region at the same time, the MV from the MPs will affect each other. In the central region of multiple MPs, the density of MV becomes the largest, while the net ionization rate of ion number density is distributed in the periphery region of the MP group.

A Study of Transient Processes in a High-Current Vacuum-Arc Anode Spot Using High-Speed Spectroscopy and Videorecording

A Study of Transient Processes in a High-Current Vacuum-Arc Anode Spot Using High-Speed Spectroscopy and Videorecording

Development and Current–Voltage Characteristic of Arc on AMF Contacts at Different Opening Speeds

This article presents the results of the investigation of high-current vacuum arcs (HCVAs) on axial magnetic field (AMF) contacts at an average opening speed of 2 m/s and the comparison of the obtained results with similar results received earlier at a lower average opening speed of 1 m/s. We compared the voltage oscillograms and the current-voltage characteristics (CVCs), as well as the arc development process of the discharges at different opening speeds. The discharge was ignited by opening the contacts in a demountable vacuum chamber and was fed with the half-sine current pulse of 10 ms in duration. For analyzing the arc development processes, high-speed video recording of the arc column and the cathode surface was conducted throughout the entire current pulse. We discovered that the process looks similar for both the investigated contact speeds: a discharge is initiated at one or more points and covers the entire contact surface in a few milliseconds. Only quantitative differences are observed due to a higher arc voltage and, accordingly, energy input at a higher speed of contact movement. The CVC of the developed arc in both cases turned out to be linear in a wide range of currents. The analysis of the CVC showed that, in the developed arc, the ratio of the resistance of the column to its length does not depend on the length of the gap and the opening speed of the contacts. Thus, we can assume that the plasma parameters in the column change little with an increase in the current and in the opening speed of contacts. This assumption is supported by the results of a discussion of the literature on the CVC of HCVAs.

Thermal Effect on AMF Electrodes at Different Opening Speeds

The erosion and thermal states at current zero for the axial magnetic field (AMF) electrodes after high-current vacuum arcs (HCVAs) were studied at an average opening speed of 2 m/s. The results obtained are compared with similar results received earlier at an average opening speed of 1 m/s. The discharge was ignited in a demountable vacuum chamber by opening the contacts and was fed with the half-sine current pulse of 10 ms in duration. To determine the thermal state of the surface of the electrodes at zero current, a Phantom MIRO M310 high-speed video camera with a Carl Zeiss 100 mm F2 lens was used. In addition, the surface of the electrodes after the arc exposure was photographed by a Canon camera. The study showed that at the same current an increase of the opening speed leads to an increase in the thermal effect on the electrodes. Besides, the work revealed that at high opening speed (HOS) the process of appearances of erosion traces on the cathodes and, especially, on the anodes, is significantly different. The estimations made in the work showed that the difference in erosion traces on the anode is associated not only with an increase in the thermal effect but also with a change in the momentum transferred to the anode by cathode jets due to jets relaxation in the interaction with the secondary anode plasma in a long arc.

Radiation Power of a High-Current Vacuum Arc Stabilized by an Axial Magnetic Field in the Visible and UV Ranges of the Spectrum

Using a silicon photodiode, we have performed measurements of the power emitted by a vacuum arc in the UV and visible spectral ranges. Measurements have been carried out upon stabilizing the arc by an axial magnetic field in high-current modes with developed anodic activity. The power of radiation emerging from the arc through the side surface is measured. The results obtained show that, when analyzing the energy balance of a high-current vacuum arc, the radiation must be taken into account.

Исследование переходных процессов анодного пятна сильноточной вакуумной дуги методом скоростной спектроскопии и видеорегистрации

The processes of plasma formation in the anode region of a high-current vacuum arc discharge are of high actuality in terms of improving the switching characteristics of vacuum circuit breaker. In present paper the dynamics of the radiation spectrum of anode region was recorded with the system that allows time scanning of a spectrum. In parallel, there was high-speed videorecording. The obtained data clearly show changes in the charge composition of the anode spot plasma in the process of changing discharge forms.

LINAC developments for heavy ion operation at GSI and FAIR

The first cavity of a standalone superconducting (sc) continuous wave (cw) heavy ion Linac as a demonstration of the capability of 217 MHz multi gap Crossbar H-mode structures (CH) has been already commissioned at high acceleration gain. The worldwide first beam test with a superconducting multi gap CH-cavity was a milestone of the R&D work of HIM and GSI in collaboration with Goethe University Frankfurt (GUF) in preparation of the sc cw heavy ion Linac project, substituting GSI-UNILAC as a heavy ion high duty factor Linac. Recently the first two of four fully equipped cw-Linac cryomodules are in procurement. To meet the future FAIR science requirements higher beam intensity has to be achieved in the present GSI-accelerator complex. In the last years ion source developments, in particular for the high current Vacuum Arc Ion Sources (VARIS), were concentrated on heavy elements, as Bi and Pb, aiming for stable routine ion source operation at a sufficient rep. rate and high production efficiency. Stripping is a key technology for all heavy ion accelerators. After upgrade of the supersonic N2-gas jet implementation of high current foil stripping, recently a new H2gas cell, using a pulsed gas regime synchronized with arrival of the beam pulse has been developed. An enhanced stripper gas density as well as a simultaneously reduced gas load results in an increased stripping efficiency, while the beam emittance remains the same. A new record beam intensity (11.1 emA) for238U28+beams at 1.4 MeV/u has been achieved, applying the pulsed high density H2-stripper target to a high intensity238U4+beam from the VARIS ion source. Further ion source developments have been accomplished recently providing for sufficient heavy ion beam intensities at the High Current Injector Linac. A machine investigation program has been performed in 2020. The focus was to optimize the entire FAIR injector chain for high intensity heavy ion beam after the successful implementation of different upgrade measures. Besides a dedicated operation mode applying UNILAC, as a heavy ion Linac, at a synchronous phase significantly lower than 30 degrees for high intensity proton beam, could be established. Thus, UNILAC is able to deliver a sufficient proton beam intensity for the FAIR commissioning phase, when the FAIR-proton Linac is not yet available.

Numerical investigation on the influence of circuit breaker structure parameters on vacuum arc behaviors

In a switchgear, an external transverse magnetic field (ETMF) is generated by the U type loop consisting of the vacuum interrupter, external busbar and conductive rod connected to the vacuum interrupter. The ETMF will make the vacuum arc deflected and strengthen the contraction of the arc. This can increase the probability of breaking failure. To weaken the adverse effect of the ETMF, the real magnetic field data of the arc area with different structure parameters when the length of conductive rod, external busbar and phase distance is changed are obtained by establishing simulation model in this paper. Taking the real magnetic field data as the boundary condition, this paper obtains the typical parameters of the vacuum arc plasma with different structure parameters by using the established three-dimensional high-current vacuum arc magnetohydrodynamics model. The simulation results show that the ETMF makes the transverse magnetic field (TMF) of the arc area asymmetric, which leads to an arc deflection. Reducing the length of the conductive rod connected to the vacuum interrupter to 50 mm can effectively improve the asymmetry of the TMF caused by the EMTF, weaken the arc deflection phenomenon, make the distribution of the plasma parameters more uniform, and increases the utilization of the anode contact surface. Moreover, it can not only reduce the heat flux density into the anode as a whole, but also reduce the heat flux density in the high heat flux density area, so as to effectively reduce the degree of anode activity and improve the negative effects caused by the anode activity. The changes of other external structural parameters have less influence on the improvement of the vacuum arc deflection phenomenon. Increasing the phase spacing to 275 mm or reducing the length of the external bus bar to 100 mm can only slightly weaken the arc deflection.

Мощность излучения сильноточной вакуумной дуги, стабилизированной аксиальным магнитным полем, в видимой и ультрафиолетовой областях спектра

A silicon photodiode, was used to measure the power emitted by a vacuum arc in the ultraviolet and visible spectral regions. The measurements were carried out with the high-current vacuum arc stabilized by an axial magnetic field in regimes with developed anode activity. The power of radiation coming out of the arc through the side surface was measured. The results show that when analyzing the energy balance of a high-current vacuum arc, radiation must be taken into account.

Mathematical Model of the Diffusion Mode of a Short, High-Current Vacuum Arc in the Axial Magnetic Field

In this paper, a theory of a diffuse mode of an axially symmetric short high-current vacuum arc in an external axial magnetic field is developed. A second-order partial differential equation for the lines of discharge current levels (2D model) is obtained. The boundary conditions at the cathode and anode boundaries of the plasma are formulated. The solution of this equation with allowance for the heat-balance equation for electrons and the equation for the plasma concentration makes it possible to determine the dependence of streamlines on the coordinates. With these lines, the obtained analytical formulas can be used to calculate the components of the current density, magnetic field, and the distribution of the electron temperature and plasma concentration in the discharge gap. A (1.5D) mathematical model (jr $$ \ll $$ jz) that significantly simplifies the calculations and has a sufficiently wide range of applicability is proposed and substantiated. The method of successive approximations, which ensures results with the required accuracy, is used in the calculations for this model. The distributions of the components of the magnetic field Br, Bθ, and Bz, the current density (jr, jz, and jθ), the distributions of the electron temperature, and the concentrations of electrons and ions in the plasma of a vacuum arc are calculated.

Investigation on anode plume in high-current vacuum arc by experiments and simulations

The objective of this paper is to investigate anode plume in high-current vacuum arc through experiments and simulations. A series of experiments are carried out in a demountable vacuum chamber at different current levels with the CuCr40 contact. Combined with arc voltage and arc image, the formation and evolution of typical anode modes, especially anode plume, are analyzed. The contact erosion and scanning electron microscopy (SEM) results are also discussed after experiments. Based on the experimental results, a two-dimensional (2D) magneto-hydro-dynamic (MHD) model is adopted to study the physical characteristics of anode plume. The experimental results show that a larger current leads to a more intense anode mode forming at smaller gap distance with a bigger and brighter arc column. Anode plume is generated between anode spot type 2 and current zero due to the obvious pressure difference between anode vapor and cathode plasma, which is confirmed by the simulation results of different anode temperatures. The contact erosion is more severe in the area where anode plumes frequently appear. The spatial distribution of number density, temperature, pressure, and electrical conductivity of anode plume are analyzed by simulations, and therefore the related experimental phenomena are explained.

Modeling and simulation of the influence of contact structure on the characteristics of high current vacuum arc plasma

With the advantages of environmental protection, small size, and light weight, the vacuum circuit breaker has been widely used in power systems. At present, it is developing toward the direction of high voltage and high current. In this paper, the magnetic field simulation model of a cup-shaped axial magnetic contact system is established, and the actual magnetic field data in the arc area are obtained as the boundary conditions, and then a three-dimensional steady-state magnetohydrodynamic model of the vacuum arc is established. The plasma parameter distribution characteristics in the vacuum arc area are studied by changing the number of slots in the contact plate, the angle of the contact cup chute, the length of the slot in the contact plate, and the central process hole. On this basis, a new type of embedded axial magnetic contact system including an embedded magnetic ring and a reverse contact cup is proposed, and the influence of changing the angle and number of inclined slots of the embedded contact cup on the arc distribution characteristics at the peak current and current zero is further studied. The simulation results show that the new structure contact is helpful to the breaking capacity of the vacuum switch and has a guiding significance for the design of the vacuum circuit breaker. By comparison, our simulation results have the same trend with the experimental results of other researchers.

Study on the influence of metal particles on the characteristics of high-current vacuum arc plasma

In the arcing process of high-current vacuum arc, the metal particles spattered from the active anode will have a significant influence on the plasma characteristics of the arc column when they entrance the interelectrode area. In this paper, the characteristics of a high-current vacuum arc with metal particle are studied by modeling and simulation. The results show that the vapor produced by metal particle will obviously cool the arc plasma and reduce the current density in the vicinity area of the metal particle. In addition, the metal particle will hinder the movement of the cathodic plasma and complicate the ion density distribution and movement process near the metal particle. Finally, an obvious ionization layer will be formed around the metal particle. When the metal vapor passes through the ionization layer, the vapor will be ionized rapidly, and an abundance of ions will be produced at the same time. The research results are of great significance for the deep understanding of arcing process of high-current vacuum arc.

Influence Mechanism of Cathode Materials on the Transition Process of Arc Modes in Drawn Vacuum Arcs Under External AMF

The objective of this article is to determine the influence mechanism of the cathode materials on the transition process of the arc modes in high-current drawn vacuum arcs under the external axial magnetic field (AMF). Six kinds of pure metal of Cu, W, Mo, Fe, Cr, and Al were selected as the cathode materials. A high-speed charge-coupled device (CCD) video camera was selected to record the arc appearance. The experimental results indicate that the cathode materials had a great effect on the arc modes in the high-current vacuum arcs with the application of AMF. Under the cathode of W and Mo, the arc modes turned to the constriction arc mode and the anode spot arc mode more easily than that under the cathode of Cu, Fe, Cr, and Al, with the increase of the arc current. For various cathode materials and same anode, the critical current density inputting to anode surface for the transform of vacuum arc modes was different. This should be caused by the differences in the constricted characteristics and the ion energy of the vacuum arcs, which took a significant effect on the transition process of the arc modes in the vacuum arcs under AMF. The higher ion energy would lead to a more active anode, which resulted in the positive ion and metal vapor from the anode. Moreover, the cathode materials played different roles in the various stages of the discharging process of the drawn vacuum arcs. The effect of cathode material on the transition process of the arc modes in the high-current vacuum arc mainly took in Stage II, which sustained from the end of the bridge arc column to the arc current peak and dominated the transition process of the arc modes.

3D modeling and simulation of high-current vacuum arc subjected to real external transverse magnetic field

Vacuum circuit breakers (VCBs) are widely used in power distribution systems. When the VCB in a switchgear interrupts the short circuit current, the U type loop, which consists of a vacuum interrupter, an external busbar and a conductive rod, generates an external transverse magnetic field (ETMF). This field deflects the vacuum arc and affects the interruption performance of the VCB. In this paper, the real magnetic field data of the arc region are obtained by establishing a simulation model of an electrode system, taking into account the real ETMF and real axial magnetic field (AMF). Furthermore, the three dimensional steady magnetohydrodynamic model of the vacuum arc is established by using real magnetic field data as the boundary condition. The vacuum arc characteristics under the combined effect of AMF and the asymmetric transverse magnetic field (TMF) are studied. The simulation results show that the ETMF considerably changes the Bx of the arc column, which demonstrates asymmetry in the positive and negative directions, whereas By demonstrates a weaker asymmetry. Moreover, the asymmetric TMF deflects the distributions of the vacuum arc plasma and increases the partial heat flux density and axial current density. With the increase in the severity of the short circuit, the TMF asymmetry of the arc region is enhanced and the deflection of the vacuum arc plasma is also enhanced.

Experimental Investigation on Anode Spots and Anode Plumes in High-Current Vacuum Arc Under Different Contact Materials

The objective of this article is to investigate the effect of contact material on the formation and transition of high-current anode spots and anode plumes. A series of experiments are carried out in a demountable vacuum chamber at three current levels of 3, 4, and 6.5 kA. Plate contacts made of CuCr30 and CuCr40 with a diameter of 10 mm are adopted. Arc images are captured by a high-speed camera and synchronized with measurements of the arc current and voltage. The experimental results show that the three typical anode discharge modes, namely footpoint, anode spot type 1, and anode spot type 2, are formed at a smaller gap distance as the experimental current increases, and this tendency is independent of the contact material. The arc voltage is higher and the anode spot appears earlier and lasts longer under the CuCr40 contact than under the CuCr30 contact. As a result, the footpoint is formed at a smaller gap distance, whereas anode spot type 2 is formed at a larger gap distance. As a special anode discharge mode, an anode plume usually occurs between anode spot type 2 and arc current zero in various shapes at different locations on the anode surface. The anode plume of the CuCr40 contact appears at a larger gap distance and the corresponding threshold current and accumulated arc energy are also larger. Due to a stronger anode activity, the anode plume lasts a longer time under the CuCr40 contact than under the CuCr30 contact.

Characteristics of High-Current Electron Gun with Plasma Anode Based on Hybrid Discharge

Spatial structure of glow and time dynamics of a hybrid discharge that combines high-current reflective discharge and vacuum arcs induced by spark breakdown on dielectric surface are studied at a supply voltage of up to 9 kV and working gas (argon) pressures of 0.1–1 mTorr. A plasma anode with an increased peripheral concentration of ions can be formed, in particular, with the aid of an auxiliary shield. Distributions of energy density are measured over the cross section of a nonrelativistic (up to 30 keV) high-current (up to 25 kA) beam generated in an electron gun with an explosive emission cathode and a plasma anode based on this (hybrid) discharge. The results are comparable with the results obtained using concentrators of magnetic field. It is expedient to employ the proposed method for improvement of uniformity of the beam, since application of the concentrators may be impossible.