Javier Sevil Serrano

Minimization of vias in PCB implementations of planar coils with litz-wire structure

PCB implementation of planar windings replicates the structure of conventional litz wires in order to reduce the ac losses. This structure consists of a set of fine trace electrically connected in parallel which are transposed by means of changes of both trajectory and layer. An appropriate transposition strategy is essential to reduce the winding ac losses, however PCBs with high number of vias could result expensive and not reliable. Taking advantage of the field profile of planar windings, in this work is studied the minimization of the number of vias without significant reduction of performance. The work is carried out by means of a combination of finite-element analysis (FEA) simulations and experimental verification on ultra-thin (0.3 mm) PCB prototypes of planar inductors oriented to a domestic induction heating application.

Design and optimization of small inductors on extra-thin PCB for flexible cooking surfaces

The following paper describes the design and optimization method for a small inductor in printed circuit board, which is later used in the implementation of a flexible cooking surface prototype. The method combines analytical developments with finite element analysis (FEA) simulations, providing an important decrease of the computational costs. This is followed by the corresponding calculations in order to minimize conduction and proximity losses in the winding by optimizing the copper volume in the winding and the conductor cross-section dimensions. A parametric analysis is carried out to define the induction system that leads to the optimal efficiency, which, moreover, proves extra-thin PCBs as the most suitable solution. A laboratory prototype of a flexible cooking surface was implemented and tested under real working conditions. The empirical characterization produced good results, which are consistent with the simulations. Additionally, the correct thermal behavior of the arrangement and its adaptability to different pot sizes was verified.

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 Maxwells 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.

Modeling of domestic induction heating systems with non-linear saturable loads

In this work, a model for induction heating cooktops with non-linear loads is presented. The model includes both the electronic converter and the inductor-pot system, which is usually modeled by its frequency-dependent equivalent impedance. Due to the non-linear relation between the magnetic field and the magnetic flux density in ferromagnetic media, the equivalent impedance of the inductor-pot system is significantly dependent on the excitation level. In this direction, two common materials have been experimentally characterized by their permeability curve for a wide range of excitation levels. Once the magnetic properties of the materials are known, a simulation model was developed including the non-linear behavior. By means of the simulation model, the equivalent impedance is obtained as a function of the excitation frequency and level. The modeled non-linear load is finally introduced in the power converter model from which the main waveforms can be extracted. Finally, the model was experimentally verified. The system was tested under real working conditions showing good concordance with the simulations.

Evolution of tactical behavior of soccer players across their development

Abstract The objective of this study was to analyse the tactical behaviour of soccer players in real-game situations across the different stages of development. The study involved 186 soccer players, aged between 8 and 19 years, from 15 teams across 3 Spanish Soccer clubs. We analysed 4409 actions over 30 league matches. The instrument used was an adaptation of the Game Performance Evaluation Tool, which measures decision-making and execution actions for passing, dribbling and shooting skills in different age groups (i.e. U10, U12, U14, U16 and U19). Our results demonstrate that in all groups the percentage of successful skill executions was lower than that of adequate decisions. Further, progression into the U10 and U14 groups interrupted the development of decision-making and skill execution actions. Based on this we propose a change to the regulatory configuration of youth and child categories that allows for a progressive adaptation to the skills and training needs of players. The training of both tactical and technical skills is also considered relevant.

Calculation of losses in PCB windings for multi-coil contactless charging systems

This work presents a method for calculating losses in PCB windings used in multi-coil contactless charging systems. This includes an electromagnetic model which combines analytical developments with FEM simulations in order to calculate the frequency-dependent resistance in a rectangular cross-sectional conductor. The obtained resistance per unit length is then applied to a PCB winding composed of multi-stranded turns in which strands rotate their positions building a Litz structure. The proposed model considers a generic case of a multi-coil assembly in which one of the inductors is supplying power to the load. As other coils may be positioned in the immediate vicinity of an alternating magnetic field source, these coils will produce a loss contribution due to proximity effect. The model has been experimentally validated and the results present consistence when compared with the calculations.