First self-resonant frequency of power inductors based on approximated corrected stray capacitances

Inductive devices are extensively employed in power electronic systems due to their magnetic energy storage and power transfer capabilities. The current trend is towards increasing the frequency of operation in order to reduce the size of the magnetic components, but the main drawback is that the parasitic capacitance effect can become significant, and degrade the performance of the system. This work analyses the influence of this stray capacitance, and considers how to improve the performance of the device. In general, the impact of the stray capacitance on a magnetic component can be reduced by two methods: reducing the parasitic capacitance between turns of the winding or, alternatively, modifying the arrangement of the connection between turns. To evaluate the last option, an approximated expression of the first self-resonant frequency of the magnetic device is proposed. This gives a rapid assessment of the performance of different devices maintaining the overall equivalent inductance. The proposed expression accounts for the influence of the connection between turns in the bandwidth of the component. Finally, some numerical results are verified with planar coils manufactured on two-layer printed circuit boards

Preliminary proposal of a metric for assessing and improving the impact of open-access heritage collections on Wikipedia

Institutions are increasingly moving toward providing access to collections digitally through open-access initiatives. Measuring this impact and providing metrics to benchmark progress remains an open challenge. This project aims to tackle part of this challenge, focusing on digitized image collections made available via Wikimedia. This work in progress is attempting to create a generalizable and consistent metric which can be used to maximize the potential impact of featuring an image from a collection within a certain Wikipedia entry. The metric considers several quantitative elements that represent specific aspects of impact and is demonstrated for a collection of landscape painting. We focus on impact through a public engagement lens, optimizing our metric to drive an increase in the number of people interacting with items in a collection. Future work will explore more advanced NLP methods and different collection types

Guiding chemical pulses through geometry: Y-junctions

We study computationally and experimentally the propagation of chemical pulses in complex geometries.The reaction of interest, CO oxidation, takes place on single crystal Pt(110) surfaces that are microlithographically patterned; they are also addressable through a focused laser beam, manipulated through galvanometer mirrors, capable of locally altering the crystal temperature and thus affecting pulse propagation. We focus on sudden changes in the domain shape (corners in a Y-junction geometry) that can affect the pulse dynamics; we also show how brief, localized temperature perturbations can be used to control reactive pulse propagation.The computational results are corroborated through experimental studies in which the pulses are visualized using Reflection Anisotropy Microscopy.Comment: submitted to Phys. Rev.

Printed circuit board coils of multi-track litz structure for 3.3 kW inductive power transfer system

This paper presents the optimization procedure of an inductive power transmission (IPT) system which utilizes large size spiral printed circuit board (PCB) coils for high- power transfer. Printed circuit boards for coil assembly provides advantages in the manufacturing process through the use of cost- effective flexible fabrication techniques. Furthermore, this kind of construction offers a low profile device, which is of great interest for applications with space constraints. PCB-based IPT system coils can achieve high energy efficiency by applying litz-structure braiding techniques, as investigated in this work, where the objective was to obtain an optimized balance between the conduc- tion losses and proximity losses associated with the number and dimensions of the traces. Considering the geometrical dimensions and manufacturing constraints, we will proceed to obtain the characteristics of the coil to achieve optimal performance. The estimation of coil losses were in part based on finite element simulations, and the results were conveniently processed with the appropriate mathematical methods. Numerical simulation and experimental results were conducted for validation on a prototype suitable to transfer up to 3.3 kW for a transmitter- receiver distance of 10 cm. In the experimental arrangement, a maximum efficiency in the coils of 93% has been measured, and the overall efficiency of 88% has been reached for the entire IPT system

Evaluation and measurement of heliostat misalignment in solar power plant using vector model

Heliostat alignment evaluation is among the main issues in solar tower concentration plant operation and maintenance. This paper describes a novel method used to evaluate heliostat misalignment and its experimental verification. This method provides a different way of visualizing beam centroid pointing errors by generating the complete deviation curve for each axis. This, for example, would be useful for verifying a heliostat’s correct alignment by using a measurement performed out of the receiver target, using these traces to calculate its reflection’s expected location, given a known misalignment. This measurement could be performed during operation simply by including a reflective element in the heliostat and two detector arrays on the tower’s surface. This model has been tested for various types of misalignments of a heliostat at different hours, dates, and heliostat locations. The simulation results have been validated by using an experimental setup at a scale of 1:100

A flexible cooking zone composed of partially overlapped inductors

Domestic induction cookers are evolving from fixed cooking areas to flexible surfaces in such a way that the pot can be placed at any position. This implies the use of a larger number of reduced-sized inductors, which present a lower efficiency. As a solution to increase the efficiency while maintaining the flexibility, we propose the use of partially overlapped inductors of a larger size. This concept is currently in use in wireless power transfer systems, where the transmitter arrangement consists of several overlapped coils. The aim of this paper is to evaluate this concept applied to domestic induction heating appliances, with special emphasis in analyzing the effects of introducing the multicoil system with dissipative media. Moreover, the losses in the winding will be studied in detail. The system will be prototyped and tested, delivering up to 3.7 kW

Analysis and design of tubular coils for wireless inductive power transfer systems

We evaluate copper tubes as alternative of litz wire for planar coils of inductive power transfer (IPT) systems. For this purpose, a design methodology focused on maximizing the product of the magnetic coupling and the quality factor is proposed. The methodology is based on a combination of FEA simulations and analytical calculations of the skin and proximity losses in the tube. Analytical calculations are based on solutions of Maxwell''s equations for a tubular geometry. These solutions are oriented to extract both skin and proximity losses in the tube. Performance of a prototype of 1.5 kW is evaluated and compared with a conventional litz-wire implementation

Analytical solution of the induced currents in multilayer cylindrical conductors under external electromagnetic sources

We present a closed-form solution for the induced losses in round conductors consisting of several concentric layers. The geometry under study corresponds to an infinitely-long and isolated multilayer cylinder where layers can have different electromagnetic properties and the number of layers is not restricted. The multilayer conductor is under an external time-varying magnetic field which induces currents and, accordingly, generates Joule dissipation. Total induced losses are obtained by integrating the losses of each layer. Mathematical expressions of the current distribution in each layer are derived from the solution of Maxwell''s equations. These expressions consist of a combination of Bessel functions of different kinds and orders. The current distribution in a particular layer not only depends on the properties of the layer but also on the properties of the rest of layers. Consequently, matrix formalism is adopted for describing current distribution of layers. Matrix description is numerically solved and results are compared with finite element simulations for different arrangements and cases

Planar and Radial Kinks in Nonlinear Klein-Gordon Models: Existence, Stability and Dynamics

We consider effectively one-dimensional planar and radial kinks in two-dimensional nonlinear Klein-Gordon models and focus on the sine-Gordon model and the $\phi^4$ variants thereof. We adapt an adiabatic invariant formulation recently developed for nonlinear Schr{\"o}dinger equations, and we study the transverse stability of these kinks. This enables us to characterize one-dimensional planar kinks as solitonic filaments, whose stationary states and corresponding spectral stability can be characterized not only in the homogeneous case, but also in the presence of external potentials. Beyond that, the full nonlinear (transverse) dynamics of such filaments are described using the reduced, one-dimensional, adiabatic invariant formulation. For radial kinks, this approach confirms their azimuthal stability. It also predicts the possibility of creating stationary and stable ring-like kinks. In all cases we corroborate the results of our methodology with full numerics on the original sine-Gordon and $\phi^4$ models.Comment: 14 pages, 15 figure

A quasi-diagonal approach to the estimation of Lyapunov spectra for spatio-temporal systems from multivariate time series

We describe methods of estimating the entire Lyapunov spectrum of a spatially extended system from multivariate time-series observations. Provided that the coupling in the system is short range, the Jacobian has a banded structure and can be estimated using spatially localised reconstructions in low embedding dimensions. This circumvents the ``curse of dimensionality'' that prevents the accurate reconstruction of high-dimensional dynamics from observed time series. The technique is illustrated using coupled map lattices as prototype models for spatio-temporal chaos and is found to work even when the coupling is not strictly local but only exponentially decaying.Comment: 13 pages, LaTeX (RevTeX), 13 Postscript figs, to be submitted to Phys.Rev.