Arc Model Research Articles

Numerical analysis of arc and molten pool behaviors in high speed tandem TIG welding of titanium tubes

A high speed tandem TIG welding process was adopted to manufacture titanium welded tubes. A coupled electrode, arc and weld pool numerical model was also developed to investigate the temperature distribution, arc plasma and molten metal flows, and energy propagation of this welding process. Under the driving of the electromagnetic force, arc plasmas under the leading and trailing electrodes flowed towards each other. The Marangoni stress was much higher than the arc shear stress, and was the main driving force for the backward molten metal flow on the top weld pool surface. The calculated arc efficiency of this welding process was 79.8%. The high speed tandem TIG welding process can improve the manufacturing efficiency and quality of titanium welded tubes.

Can Hip Passive Range of Motion Predict Hip Microinstability? A Comparative Study

Background: Hip microinstability is an increasingly recognized cause of pain and disability in young adults. It is unknown whether differences in passive hip range of motion (ROM) exist between patients with versus without hip microinstability. Hypothesis: Underlying ligamentous and capsular laxity will result in differences in clinically detectable passive ROM between patients with femoroacetabular impingement (FAI), patients with microinstability, and asymptomatic controls. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A retrospective review of all patients undergoing hip arthroscopy between 2012 and 2018 was conducted. Patients with a diagnosis of isolated microinstability based on intraoperative findings were identified and classified as having isolated FAI, instability, or FAI + instability. Patients without a history of hip injury were included as controls. Range of motion was recorded in the supine position for flexion, internal rotation, and external rotation. Univariate and multivariate analysis was performed on each measurement in isolation as well as combinations of motion to include total rotation arc, flexion + rotation arc, and flexion + 2× rotation arc Models were then created and tested to predict instability status. Results: In total, 263 hips were included: 69 with isolated instability, 50 with FAI, 50 with FAI + instability, and 94 control hips. A higher proportion of patients in the instability and FAI + instability groups were female compared with the FAI and control groups ( P < .001). On univariate analysis, differences were found in all groups in all planes of motion ( P < .001). Multivariable analysis demonstrated differences in all groups in flexion and flexion + rotation arc. In symptomatic patients, the best performing predictive model for hip microinstability was flexion + rotation arc ≥200° (Akaike information criterion, 132.3; P < .001) with a sensitivity of 68.9%, specificity of 80.0%, positive predictive value of 89.1%, and negative predictive value of 51.9%. Conclusion: Patients with hip microinstability had significantly greater ROM than symptomatic and asymptomatic cohorts without hip microinstability. Symptomatic patients with hip flexion + rotation arc ≥200° were highly likely to have positive intraoperative findings for hip microinstability, whereas instability status was difficult to predict in patients with a flexion + rotation arc of <200°.

A novel dynamic parameter method (DPM) based on ANN for safety assessment of corroded pipelines

Corrosion in oil and gas pipelines is inevitable, which seriously affects the safety of pipelines. The safety assessment of corroded pipelines is a matter of urgency. To describe the damage behavior of pipelines, the Chen-Chu criterion was proposed. However, a key parameter in Chen-Chu criterion was determined empirically. In this paper, a novel dynamic parameter method (DPM) is proposed to determine the key parameter based on artificial neural network (ANN). The empirical parameter in Chen-Chu criterion is optimized by ANN and turns into dynamic one varying with input. The data for training in ANN is obtained by double circular arc (DCA) model. Compared to finite element method and previous prediction equations, the DPM are closer to the experimental data. Besides, by comparing with the experimental data, it is found that DPM is even more accurate than direct ANN method. It provides a new idea for the fusion of solution of traditional methods and data-driven methods.

Fluid-chemical modeling of the near-cathode sheath formation process in a high current broken in DC air circuit breaker

When the contacts of a medium-voltage DC air circuit breaker (DCCB) are separated, the energy distribution of the arc is determined by the formation process of the near-electrode sheath. Therefore, the voltage drop through the near-electrode sheath is an important means to build up the arc voltage, which directly determines the current-limiting performance of the DCCB. A numerical model to describe the near-electrode sheath formation process can provide insight into the physical mechanism of the arc formation, and thus provide a method for arc energy regulation. In this work, we establish a two-dimensional axisymmetric time-varying model of a medium-voltage DCCB arc when interrupted by high current based on a fluid-chemical model involving 16 kinds of species and 46 collision reactions. The transient distributions of electron number density, positive and negative ion number density, net space charge density, axial electric field, axial potential between electrodes, and near-cathode sheath are obtained from the numerical model. The computational results show that the electron density in the arc column increases, then decreases, and then stabilizes during the near-cathode sheath formation process, and the arc column’s diameter gradually becomes wider. The 11.14 V–12.33 V drops along the 17 μm space charge layer away from the cathode (65.5 kV/m–72.5 kV/m) when the current varies from 20 kA–80 kA. The homogeneous external magnetic field has little effect on the distribution of particles in the near-cathode sheath core, but the electron number density at the near-cathode sheath periphery can increase as the magnetic field increases and the homogeneous external magnetic field will lead to arc diffusion. The validity of the numerical model can be proven by comparison with the experiment.

Multicharacteristics Arc Model and Autocorrelation-Algorithm Based Arc Fault Detector for DC Microgrid

DC microgrids contribute to the increasing penetration of renewable energies. However, a DC arc fault will lead to malfunctions and even fire hazards in a DC microgrid. To ensure the safe and efficient operation of a DC microgrid, the characteristics of DC arc faults should be determined, and a reliable arc-fault detection technique is required. Nevertheless, it is difficult to investigate the DC arc faults in a practical system. Thus, an accurate and reliable arc model for simulation research of arc faults is significant. Since a DC microgrid has numerous branches, the existing arc models cannot express the complex and random characteristics of potential arc faults. Besides, the detection points need to be determined for the appropriate installation of arc fault detectors. Furthermore, the arc features may be ambiguous and affected by the environmental noise and power electronics noise leading to nuisance tripping to arc detectors. In this paper, a multi-characteristics arc model is established based on the volt-ampere, current sag, and power spectral characteristics of arc faults. According to the frequency domain features of arc faults and interaction effects between different branches, the arc-detection-point selection principle is formed. A non-invasive arc fault detector based on magnetic-field sensing and autocorrelation algorithm is developed. It can avoid the effects of periodic environmental noise and power electronics noise by comparing the correlation between arc features in periods. The experimental results verify that the arc faults can be detected with high accuracy by installing the autocorrelation-algorithm-based arc detector at detection points selected by the arc-detection-point selection principle in a DC microgrid.

An Improved Coupled FE–Circuit Model for Turn-to-Turn Short-Circuit Faults Inside Converter Transformers

Turn-to-turn short-circuit (TTSC) faults, which are among the most common and potentially threatening faults inside large-capacity converter transformers, can lead to catastrophic accidents and causalities. Due to the lack of a proper model, the reproduction and analysis of actual TTSC faults remain difficult challenges. In this paper, converter transformer TTSC faults are numerically investigated through directly coupling an internal finite element (FE) model with a model of the external electric circuit. In every calculation step, data are automatically transferred between the FE and circuit domains, and the simulations for the winding magnetic leakage flux and fault current are executed simultaneously. Furthermore, the Hochrainer arc model is used to simulate the nonlinear conductance of the low-impedance arc shorting adjacent turns; this model is directly integrated into the short-circuit loop by means of user-defined code. A realistic 405.2 MVA/500 kV single-phase three-core-limb converter transformer within an ultra-high voltage (UHV) converter system is modeled as a simulation case and subjected to various TTSC faults. Direct comparisons reveal agreement between the calculated results and the recorded fault data, indicating that the approach can reproduce actual faults, thus offering advantages as a replacement for dangerous and costly on-site short-circuit tests in converter transformers.

A Computational Magnetohydrodynamic Modelling Study on Plasma Arc Behaviour in Gasification Applications

The application of direct-current plasma arc furnace technology to the problem of coal gasification is investigated using computational multiphysics models of the plasma arc inside such units. An integrated modelling workflow for the study of DC plasma arc discharges in synthesis gas atmospheres is presented. The thermodynamic and transport properties of the plasma are estimated using statistical mechanics calculations and are shown to have highly non-linear dependencies on the gas composition and temperature. A computational magnetohydrodynamic solver for electromagnetically coupled flows is developed and implemented in the OpenFOAM® framework, and the behaviour of three-dimensional transient simulations of arc formation and dynamics is studied in response to different plasma gas compositions and furnace operating conditions. To demonstrate the utility of the methods presented, practical engineering results are obtained from an ensemble of simulation results for a pilot-scale furnace design. These include the stability of the arc under different operating conditions and the dependence of voltage–current relationships on the arc length, which are relevant in understanding the industrial operability of plasma arc furnaces used for waste coal gasification.

AC Series Arc Fault Modeling for Power Supply Systems Based on Electric-to-Thermal Energy Conversion

The measured voltage waveform of the arc fault for the 220 V power supply system is continuous but non-smooth which is hard to be reproduced with the traditional arc models. Consequently, this paper proposes an arc model based on electric-to-thermal energy conversion. Both the heat convection loss and the heat conduction loss are considered in this arc model. This proposed arc model is specially used to simulate the arc-circuit interaction during the whole development process of the continuous-arc-fault for the 220 V power supply system. Due to the fact that this proposed arc model is a multivariable-nonlinear differential equation, this paper proposes a computation method based on the current region splitting according to the non-smooth connections of the measured voltage waveform. The model parameters can be adjusted independently in each current region. Then the comparisons between measurements and the arc model results are given which show a good agreement in the all current regions. In addition, the effective estimations for the arc geometrical and electrical parameters are achieved based on this proposed arc model. Finally, experimental results validate that the arc model and the corresponding computation method proposed in this paper are general and effective for the 220 V power supply system.

Study on magnetically blown arc characteristics and the resulting contact erosion mechanisms of high-power DC relays

High-power DC relays are widely used in new energy power systems and DC distribution networks, and commonly use transverse magnetic fields to accelerate arc extinguishing. In this paper, the magnetically blown arc characteristics and the resulting contact erosion mechanisms of high-power DC relays are studied by experiments and simulations. The experiments are carried out to analyze the arc motion, contact erosion mass, and contact morphologies, and to verify the simulation model. Considering the energy transfer source term, the establishment of a more perfect magnetohydrodynamic arc model is accomplished, and an erosion model is further established. The results indicate that the magnetically blown arcing process has three stages while the arc shapes and motion characteristics are different, and the heat flux acting on the contact can be accurately obtained by the arc model. The greater external transverse magnetic field is more conducive to extinguishing the arc and reducing the arc erosion time. In contrast, the Archimedes force plays a very small positive role and the self-induced magnetic field of the arc has a negative effect. For contact erosion, the temperature distribution of the molten pool appears trailing effect. Moreover, the advanced mathematical model proposed for erosion mass has good accuracy. The calculation results of erosion rates show that Cr reduces erosion while the current increases erosion nonlinearly. Besides, the flow and deformation characteristics of the molten pool will lead to convex strip-shaped erosion traces and arcing position transfer, and the moving erosion will cause the lateral accretion effect. Furthermore, the analysis shows that the reason for edge droplet sputtering is the pressure difference caused by Plateau–Rayleigh instability, and optimization suggestions for reducing contact erosion are given.

Word production and comprehension in frontotemporal degeneration: A neurocognitive computational Pickian account

Over a century ago, Arnold Pick reported deterioration of word production and comprehension in frontotemporal degeneration, now a common finding. Individuals with semantic dementia (SD) and behavioral variant frontotemporal dementia (bvFTD) present with word retrieval difficulty, while their comprehension is less affected. Computational models have illuminated naming and comprehension in poststroke and progressive aphasias, including SD, but there are no simulations for bvFTD. Here, the WEAVER++/ARC model, previously applied to poststroke and progressive aphasias, is extended to bvFTD. Simulations tested the hypothesis of a loss of activation capacity in semantic memory in SD and bvFTD, caused by network atrophy (Pick, 1908a). The outcomes revealed that capacity loss explains 97% of the variance in naming and comprehension of 100 individual patients. Moreover, capacity loss correlates with individual ratings of atrophy in the left anterior temporal lobe. These results support a unified account of word production and comprehension in SD and bvFTD.

Accounting for word production, comprehension, and repetition in semantic dementia, Alzheimer’s dementia, and mild cognitive impairment

It has been known since Pick (1892, 1904) that word retrieval is commonly impaired in left temporal lobe degeneration. Individuals with semantic dementia (SD), Alzheimer’s dementia (AD), and mild cognitive impairment (MCI) present with word retrieval difficulty, while comprehension is less affected and repetition is preserved. Whereas computational models have elucidated performance in poststroke and progressive aphasias, including SD, simulations are lacking for AD and MCI. Here, the WEAVER++/ARC model, which has provided neurocognitive computational accounts of poststroke and progressive aphasias, is extended to AD and MCI. Assuming a loss of activation capacity in semantic memory in SD, AD, and MCI, the simulations showed that severity variation accounts for 99% of the variance in naming, comprehension, and repetition at the group level and 95% at the individual patient level (N = 49). Other plausible assumptions do less well. This supports a unified account of performance in SD, AD, and MCI.

Influence of the aerodynamic flow on the dynamic characteristics of a lightning sweeping arc

Lightning arc attachments during swept strokes are key information in the lightning protection design of fast-moving aircraft, wind turbines, rockets, etc. However, numerical modeling has not achieved success to predict the movement of lightning sweeping arcs due to the limited understanding of the complex multi-physics convolution in the arc fluid at present. This work builds a dynamic magneto-hydrodynamic (MHD) arc model based on the setup in the laboratory simulation of the lightning continuing current and couples the electric–magnetic–thermal–force processes to get insights into the lightning arc dynamics. The MHD theory and Newton’s second law of motion are also incorporated to describe the movement of arc segments in the conditions of aerodynamic flows with different intensities. Results show that, at the center region of the arc, the electromagnetic force, thermal buoyancy, and aerodynamic force are competitive, and all are determiners in predicting the arc displacement. In contrast, at the root region of the arc, the electromagnetic force dominates the arc movement with a flow speed under 10 m/s, while aerodynamic force takes the dominant role when the flow speed exceeds 50 m/s. The arc sweeping distance expands from 0.02 to 1.01 m as the aerodynamic flow increases from 5 to 200 m/s. Meanwhile, when increasing the pitch angle of the arc-connected surface, the arc root becomes more attached to the surface and the sweeping distance is predicted to get reduced. The conclusions offer references to construct a numerical model and predict the complex arc movement during lightning sweeping strokes.

Accelerating physics-informed neural network based 1D arc simulation by meta learning

Physics-informed neural networks (PINNs) have a wide range of applications as an alternative to traditional numerical methods in plasma simulation. However, in some specific cases of PINN-based modeling, a well-trained PINN may require tens of thousands of optimizing iterations during training stage for complex modeling and huge neural networks, which is sometimes very time-consuming. In this work, we propose a meta-learning method, namely Meta-PINN, to reduce the training time of PINN-based 1D arc simulation. In Meta-PINN, the meta network is first trained by a two-loop optimization on various training tasks of plasma modeling, and then used to initialize the PINN-based network for new tasks. We demonstrate the power of Meta-PINN by four cases corresponding to 1D arc models at different boundary temperatures, arc radii, arc pressures, and gas mixtures. We found that a well-trained meta network can produce good initial weights for PINN-based arc models even at conditions slightly outside of training range. The speed-up in terms of relative L2 error by Meta-PINN ranges from 1.1× to 6.9× in the cases we studied. The results indicate that Meta-PINN is an effective method for accelerating the PINN-based 1D arc simulation.

The Electrical Behaviour of Railway Pantograph Arcs

Electric arcing is an unavoidable consequence of the current collection process by sliding contact in railways and metros, and in general in many electrified transportation systems (ETSs). The most relevant consequences in an electrical perspective are: the occurrence of transients triggering resonant behaviour and transient responses, reduction of the energy efficiency of the system, conducted and radiated disturbance, in particular for the new radio systems widely employed for signalling and communication. The involved parameters are many (type of materials, current intensity, DC and AC supply, relative speed, temperature), as well as the studied characteristics (arc instability and lifetime, dynamic behaviour, electrical system response, radiation efficiency and coupling to external radio systems). This work reports the state of the art in arc modelling, arcing experimental characterisation, interaction with the supply system, radiated emissions and disturbance to radio systems, providing a complete description of phenomena and of reference data, critically discussing similarity and differences between sources. Proposed arc models are many with different assumptions and simplifications for various applications, so that a critical review and discussion are a necessity, considering the many different approaches and not-so-obvious applicability. The comparison with experimental results highlights unavoidable discrepancies, also because of intrinsic arc variability and for the many involved parameters and operating conditions. The impact of the arc as embedded in the railway system is then considered, speaking of conducted and radiated phenomena, including interference to radio communication systems and arc detection. The most prominent effect for conducted emissions is the excitation of system resonances, including the LC filters onboard rolling stock and substations in DC railways, with consequences for disturbance and energy efficiency, and this is discussed in detail. Conversely, for high frequency emissions, the attenuation along the line circuit is significant and the effective distance of propagation is limited; nevertheless radiated electromagnetic field emissions are a relevant source of disturbance for radio systems within the ETS premises and outside (e.g., at airports). The published approaches to quantify performance reduction are discussed with emphasis on experimental methods.

Investigation on Arc Asynchronous Characteristics of the Double Bridge-Type Contacts in DC Relays

The asynchrony of the multi-break dc relay has an important influence on its arcing characteristics. Through the experimental test platform, the arc characteristics of the single bridge-type contact and the double bridge-type contacts are compared. Arc images are acquired through high-speed photography. On the basis of asynchronous action, the influence of action speed and overtravel difference on arcing characteristics is analyzed. A multi-breakpoint asynchronous arc model is established to study the nonlinear relationship between overtravel difference and arc duration. The distribution characteristics of the double-bridge arc are analyzed. Experiments and simulations show that the double bridge-type contacts have better arc-extinguishing characteristics. Increasing breaking speed is conducive to reducing arc energy difference between fractures. When the overtravel difference is small, the bridge <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B$</tex-math> </inline-formula> (bridge with larger overtravel) arc can enter the diffusion state, and the arc voltage of bridge <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B$</tex-math> </inline-formula> is higher. Reducing the overtravel difference can effectively reduce the arc duration.

Magneto-hydrodynamic simulation study of direct current multi-contact circuit breaker for equalizing breaking arc

This work is based on a direct current (DC) natural current commutation topology, which uses load-carrying branch contacts carrying rated current and multiple sets of series arcing branch contacts in parallel to achieve circuit breaking. The proposed topology can meet the new requirements of higher voltage DC switches in aviation, aerospace, energy and other fields. First, a magneto-hydrodynamic arc model is built using COMSOL Multiphysics, and the different arc breaking characteristics of the arcing branch contacts in different gas environments are simulated. Then, a voltage uniformity coefficient is used to measure the voltage sharing effect in the process of dynamic interruption. In order to solve the dispersion of arcing contact action, a structural control method is adopted to improve the voltage uniformity coefficient. The uniform voltage distribution can improve the breaking capacity and electrical life of the series connection structure.

Position linearity analysis of circular arc terminated resistive anode using finite element method for photon-counting imaging detectors.

This study proposes a comprehensive model of the circular arc terminated (CAT) resistive anode based on the finite element method to explore the dynamic process of charge diffusion on this anode and its position linearity performance. The waveforms of charges of the electrodes on the anode are calculated for different electrical parameters and their influence on positional linearity is investigated. The influence of the signal development time and the non-uniformity of the resistance per square of the anode on positional linearity is also analyzed. The results of simulations show that the non-linearity of the image varies monotonically with the termination resistance and the non-uniformity of the resistance per square of the anode, but has a non-linear relationship with the signal development time and the ratio of the resistance per square. A CAT resistive anode with capacitance c and a resistance per square of the sensitive area of R▱ can be used to recover an image with a root mean-squared non-linearity of 2%, when the charge signals of the electrode are collected for at least 0.6R▱c s. The reliability of the results of the simulations was verified with experimental measurements.

Effect of protrusion shape on film cooling performance for the cylindrical hole embedded in a contoured crater

The cratered film-cooling hole is regarded as one of the potential applications with high cooling performance and low cost. This study focuses on the influence of the protrusion shape for the contoured crater embedded in the cylindrical hole. Four protrusion shapes, i.e., arc, rectangle, trapezoid, and triangle, are considered. The cooling effectiveness, flow structure, and aerodynamic loss for the cratered holes at blowing ratios of 0.5-2.5 are obtained using the numerical method with the shear stress turbulence model. The numerical results indicate that the arc and triangle protrusion models provide better lateral coolant coverage and higher area-averaged cooling effectiveness at higher blowing ratios, attributed to the ascendant anti-kidney-shaped vortex pair. The rectangle protrusion model provides the lowest area-averaged cooling effectiveness because the kidney-shaped vortex pair dominates the downstream flow field. For the aerodynamic loss, the largest total pressure loss coefficient occurs for the rectangle protrusion model and nearly equivalent values for the other three protrusion models. The contoured cratered holes with arc and triangle protrusions are generally recommended.

Optimization of the Black-Box Arc Models for DC Current Limiting Circuit Breakers Using Levenberg-Marquardt Algorithm

Optimization of the Black-Box Arc Models for DC Current Limiting Circuit Breakers Using Levenberg-Marquardt Algorithm

Spike Surge and Conducted EMI Simulation of DC Brush Motor Considering Steady Arc at Mechanical Contacts

This study provides a circuit analysis model of a DC brush motor to predict spike surges at mechanical contacts and conducted EMI by considering the behavior of steady arc discharge. The mechanical contacts model comprises multiple variable resistors, constant voltage sources, ideal diodes, and stray capacitances. In the proposed model, spike surges with steady arc could be predicted with 90% accuracy. Moreover, simulated conducted EMI according to CISPR 25 standard is deviated from the measured value at a maximum of 25dB. Therefore, it is demonstrated that the quantitative prediction of conducted EMI requires consideration of a showering arc model at mechanical contacts.