A Novel Model of Electromechanical Contactors for Predicting Dynamic Characteristics

To ensure the reliability of power supply, a dual power supply structure appears in the power distribution system. Power supply switching is a complex physical process. This paper presents a novel model of electromechanical contactors. This model can simulate the multi-physics process of power switching. This article completes the simulation framework for power switching through contactors for the first time. Among them, the structural topology for contactors is also proposed. On the basis of the novel structure topology, an equivalent magnetic circuit model is established to calculate the relationship between driving force, flux linkage, current, and displacement. Then, a co-simulation model is established between the above equations and Adams to obtain the speed characteristics and flight time of the contactor. Subsequently, through the use of Fluent and its secondary development, a magnetohydrodynamic model is established, and the above-mentioned velocity characteristics are imported into it to analyze the arcing characteristics of the contacts under the conditions of the transverse magnetic field and the insulating grid. The effectiveness of power switching is judged by comparing the flight time of the electromechanical model and the arcing time of the magnetohydrodynamic model. The prototype is manufactured and tested on the basis of simulation. Through experimental waveforms and high-speed photography, the accuracy of the simulation model and the practicability of the contactor are verified.

Wing-wing Interaction - When Exoplanets interact with each other

<p>Electromagnetic Star-Planet Interaction is a phenomenon that occurs when a planet is sufficiently close to its host star that Alfvén waves propagate to the star and can leave an imprint on the star. The resulting structure is called Alfvén wing. Stars also often have open field-line structures due to the influence of the stellar wind. In these open field line regions, two planets can share the same set of field lines at the same time. Therefore, it is possible that Alfvén wings interact with each other and cause a time-variability in the signal. We call this process wing-wing interaction. To understand wing-wing interaction further, we apply a three dimensional, fully time-dependent, magnetohydrodynamic model. There, we simulate two planets that generate star-planet interaction and eventually undergo wing-wing interaction. We present the temporal evolution of the Alfvén wings and of the Poynting flux. From these results, we can estimate how wing-wing interaction could appear in observations. </p>

Comment on “Stepped pressure profile equilibria in cylindrical plasmas via partial Taylor relaxation” [J. Plasma Physics (2006), vol. 72, part 6, pp. 1167–1171]

In an early study of the properties and capabilities of the multiregion, relaxed magnetohydrodynamic model, Hole, Hudson & Dewar claim that they are able to construct a multiregion stepped pressure cylindrical equilibrium which does not require the existence of surface currents. We present a brief argument showing that this claim is incorrect, and clarify the meaning of their statement. Furthermore, even with the statement clarified, we demonstrate that it is not possible to find solutions to reproduce the equilibrium corresponding to the parameters given in the article. We invite the authors to provide a corrigendum with the correct values of the equilibrium they constructed.

Steady-state flows in a visco-resistive magnetohydrodynamic model of tokamak plasmas with inhomogeneous heating

The axisymmetric visco-resistive magnetohydrodynamic steady states allowing flows (i.e. non-vanishing velocity fields) are computed for a toroidal JET-like geometry. It is shown that a spatially inhomogeneous heating of moderate magnitude leads to an increase of typical toroidal speeds with respect to the situation with uniform temperature with identical mean Hartmann numbers. A symmetry argument is introduced to capture the symmetry breaking, induced by the temperature gradient, that produces a net toroidal plasma flow.

The propagation of linear waves in high-energy-density magnetoplasmas using a relativistic quantum magnetohydrodynamic model

The propagation characteristics of linear waves in high-energy-density magnetoplasmas are investigated using a relativistic magnetohydrodynamic model based on the framework of relativistic quantum theory. Based on the covariant Wigner function approach, a relativistic quantum magnetohydrodynamic model is established. Starting from the relativistic quantum magnetohydrodynamic equations and the Maxwell equations, the dispersion equation for relativistic quantum magnetoplasmas is derived. The contributions of both quantum effects and relativistic effects are shown in the dispersion relations for perpendicular, parallel propagation with respect to a background magnetic field. Results show that the corrections of both quantum effects and relativistic effects are significant when choosing the plasma parameters of laser-based plasma compression schemes.