On velocity skin effect &amp;#x2014; Part I: Physical principle analysis and equivalent models simulation

Velocity skin effect (VSE) is a kind of current clustering phenomenon, which occurs at the sliding contact interfaces between the high-speed armature and the stationary rails of electromagnetic railgun launchers. Serious current clustering is disadvantageous to the launching performance. The typical current clustering phenomena in static conductors are classified, and the physical principle of VSE is analyzed in this paper. The physical principle in rails is just skin effect because of the short rise time of the accepted pulse current, and the physical principles in armature are clustering near small source and clustering along short path of steady current owing to the continuity characteristic or Laplace equation. The corresponding methods to restrain VSE are deduced and classified as follows: 1) lengthening the contact surface; 2) adding a hard and resistive cladding on the rail's sliding surface; 3) narrowing the interface; 4) adopting a U-shaped armature instead of cuboid one; and 5) controlling the armature legs' thickness/width distribution. An equivalent 3-D model for VSE is adopted, and simulation is carried out for a complex form of armature leg. The uniform current in the interfaces is accomplished, with which the typical uniform index is about 66%. VSE is restrained according to the simulation result. The physical principle, the relevant restraining methods, and the equivalent model are significant to railgun research work.

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“…Referring to Fig. 4, an equivalent model [18] can be designed to simulate the restraining extent on VSE, as shown in Fig. 5.…”

Section: A Equivalent Model For Simulationmentioning

confidence: 99%

Physical Principle and Relevant Restraining Methods About Velocity Skin Effect

Xiang

Lei

et al. 2015

IEEE Trans. Plasma Sci.

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“…The current distribution of the PCS is affected by the VSE when the HST operates at 350 km/h; the velocity skin depth δ v [28, 29] is defined by

δ_{v} = k_{e} {(4 w / (π σ_{normalm} μ v))}^{1 / 2}

where k e indicates the comparability between the saw tooth wave and the sine form current [28] (in our case k e = 1), w is the interface length of the contact region (here the width of the pantograph strip), and v is the pantograph speed with respect to the catenary.…”

Section: Modelling and Verificationmentioning

confidence: 99%

Multi‐physics analysis and optimisation of high‐speed train pantograph–catenary systems allowing for velocity skin effect

et al. 2020

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A pantograph–catenary system (PCS) – an essential component to supply a high‐speed train (HST) – faces a variety of new challenges due to the continuously increasing train speeds. The HST traction system receives power via an electrical contact between the pantograph strip and the high‐voltage contact wire. This electrical contact is subject to serious mechanical shocks and significant electrochemical corrosion, making the modelling of the dynamic processes complicated, especially under high‐speed and heavy‐load conditions. The damage to the PCS – which is particularly noticeable at the edges of the pantograph strip – may become severe as the speed of the train rises. Moreover, as the speed increases, the distribution of the electrical current in the strip becomes uneven due to the velocity skin effect (VSE). To assess the impact of the VSE on the performance of PCSs, a multi‐physics model has been created and is reported in this study. The model has been validated through experiments and the main aspects of its functionality – such as the VSE, friction, and air convection – have been identified and analysed at different speeds. The impact of speed on the traction current and the behaviour of thermal sources have been explored. With the increasing speed, the phenomenon of current clustering at the trailing edge of the strip becomes quite dramatic, resulting in a thermal surge in the region of the strip with high current density. To mitigate the negative impact caused by VSE in the PCSs, an improved kriging optimisation methodology has been utilised to optimise the parameters of the PCS. Recommendations regarding the optimal design of the PCS are put forward to improve the current‐carrying performance and reduce the local temperature rise in the strip.

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“…Three models were composed to contrastively express the different thickness distribution of the armature leg. The equivalent simulation was adopted to show the current distribution on the sliding contact interface and the optimal extent of restraining VSE [3].…”

Section: Optimal Model Design and Equivalent Simulation To Restrmentioning

confidence: 99%

“…However, the relevant effective methods constraining VSE have not been analyzed and classified systematically. The former paper [3] summarized the physical principle of VSE.…”

Section: Introductionmentioning

confidence: 99%

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On velocity skin effect — Part II: Restraining method analysis and optimal design simulation

Lei

et al. 2014

2014 17th International Symposium on Electromagnetic Launch Technology

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Velocity skin effect (VSE) is a kind of current clustering phenomenon, which occurs in the sliding contact interfaces between the hypervelocity armature and the stationary rails for electromagnetic railgun, disadvantageous to launchers performance. The physical principle of VSE is Skin Effect of pulsed current in rails, and Clustering Near Small Source and Clustering Along Short Path of steady current in armature. The corresponding methods to restrain VSE was deduced and classified in this paper as the followings: 1) to lengthen the contact surface according to the velocity skin depth expression, 2) to add a hard and resistive cladding on the rail's sliding surface and 3) to narrow the interface considering the Clustering Near Small Source, 4) to adopt U-shaped armature instead of cuboid armature and 5) to control the armature legs' thickness distribution owing to Clustering Along Short Path. The equivalent 3-D models for VSE were adopted and the contrastive simulations were carried out for three kinds of armature's legs. The most uniformed distribution of current in three interfaces was accomplished, with which the typical uniform index is about 66%. The conclusion reached was that the general use of five methods and reasonable design could effectively restrain velocity skin effect.

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On velocity skin effect — Part I: Physical principle analysis and equivalent models simulation

Cited by 4 publications

References 15 publications

Physical Principle and Relevant Restraining Methods About Velocity Skin Effect

Physical Principle and Relevant Restraining Methods About Velocity Skin Effect

Multi‐physics analysis and optimisation of high‐speed train pantograph–catenary systems allowing for velocity skin effect

On velocity skin effect — Part II: Restraining method analysis and optimal design simulation

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On velocity skin effect &#x2014; Part I: Physical principle analysis and equivalent models simulation

Cited by 4 publications

References 15 publications

Physical Principle and Relevant Restraining Methods About Velocity Skin Effect

Physical Principle and Relevant Restraining Methods About Velocity Skin Effect

Multi‐physics analysis and optimisation of high‐speed train pantograph–catenary systems allowing for velocity skin effect

On velocity skin effect &#x2014; Part II: Restraining method analysis and optimal design simulation

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On velocity skin effect — Part I: Physical principle analysis and equivalent models simulation

On velocity skin effect — Part II: Restraining method analysis and optimal design simulation