Experimental Method for Characterizing Electrical Steel Sheets in the Normal Direction

This paper proposes an experimental method to characterise magnetic laminations in the direction normal to the sheet plane. The principle, which is based on a static excitation to avoid planar eddy currents, is explained and specific test benches are proposed. Measurements of the flux density are made with a sensor moving in and out of an air-gap. A simple analytical model is derived in order to determine the permeability in the normal direction. The experimental results for grain oriented steel sheets are presented and a comparison is provided with values obtained from literature

Etude par diffusion Raman du diagramme de phases (P, T) d'un compose presentant des phases incommensurables : le tetrathylammonium tetrachlorozincate (TMATC-Zn)

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Design of a Medium Frequency High Power Transformer built with thin Grain Oriented Electrical Steel Core

The paper addresses the problematic of a medium frequency transformer prototype design using grain oriented electrical steel (GOES) core with the future aim to build a solidstate transformer (SST) for DC grids. SSTs are electronic components using static converters connected at the primary and the secondary sides of a medium or high frequency transformer. This technology enables smart nodes for an active control of power flow within DC grids. In most of the reported cases, SSTs combine amorphous or nanocrystalline magnetic materials for the core and wide-bandgap semiconductors technologies with complex control strategies. This makes those SSTs expensive. The paper suggests another approach for designing low-cost SSTs taking advantage of widespread GOES associated to well-known silicon-based semiconductor converters working with very simple command strategies. The study focuses on a prototype dedicated to answer questions raised by the optimal design of a MFGO transforme

High power density medium frequency transformer built with thin GO electrical steel sheets

International audienceThe paper presents the concept of a medium frequency transformer built with thin grain oriented electrical steel (GOES) sheets and high temperature windings; this transformer will be associated with power converters for building a solid-state transformer (SST) used in DC grids. The aim of the study is to bring answers about the maximum operating frequency and flux density that provide the maximum power density and efficiency. A thermal model built from tests on the prototype is presented. This thermal model gives a prediction of the transformer performance for the initial choices of frequency ant flux density. It opens perspectives for designing high power density medium-frequency (MF) transformers

Évaluation d'un transformateur electronique doté d'un noyau en acier électrique à grains orientés

La part croissante des énergies renouvelables intermittentes nécessite des modifications importantes du réseau électrique. L'introduction de noeuds intelligents où le transfert de puissance peut être ajusté en temps réel devient un atout important pour l'équilibre global du réseau. Ces fonctions sont assurées par des « Solid-State Transformers (SST) » composés de transformateurs associés à des convertisseurs électroniques. L'article propose une approche complémentaire par rapport aux solutions existantes : le transformateur est basé sur un noyaux enroulé en acier électrique à grains orientés. La solution proposée exploite les bonnes propriétés du matériau aux fortes inductions et aux températures élevées. Mots-clés-Acier magnétique à grain orienté (Grain Oriented Electrical Steel-GOES), transformateur moyenne fréquence (TMF), Solid-State Transformer (SST)

Interest of square voltages for Solid State Transformer operation with Grain Oriented Electrical Steel wound core

This paper presents a comparison between core losses within Grain Oriented Electrical Steel (GOES) wound core, under sinusoidal and rectangular voltage excitations at the same operating frequency and peak flux density. Firstly, results issued by finite elements modeling and measurements are presented and discussed. Secondly, Fourier series are used to calculate the losses induced by the square voltage by adding the contribution of its harmonics, then compared to the sinusoidal case. The different approaches show that for the same operating frequency and induction, the losses under square excitation are lower than the sinusoidal one, this result is the main topic of this paper

Assessments of High-Power Solid State Transformers based on Grain-Oriented magnetic cores

International audienceAll fields of activity using electric energy are more than ever challenged for efficiency and versatility of energy flow at reasonable costs. The emergence of electronic components with high voltage and current capabilities enables to cope with those challenges. The paper deals with assessments on Medium Frequency (MF) high-power Solid State Transformer (SST). A good technical-economic balance can be achieved by assembling suitable high power SST cells made with mature technologies for power electronics, magnetic cores and simple and reliable control strategies. In this framework, the study and design of a SST based on elementary cells involving a Grain Oriented Electrical Steel (GOES) core is addressed

Solid State Transformer based on Grain-Oriented Electrical Steel Wound Cores

Considering the progress in semiconductor technology and magnetic core material performances, an increased attention is paid to the so called Solid-State Transformers (SST). Besides the ability to monitor the direction of the power flow compared to classical 50/60 Hz transformers, these devices, composed of power converters placed each side of a high frequency power transformer, offer many advantages such as small size and low weight. The main focus of this paper is to report about the transformer itself as a key element of the SST. Thin grain oriented electrical steel (GOES) has been chosen for building the core of the transformer. Reasons for this choice are the high saturation polarization capability even at high temperature and its availability on a large scale compared to amorphous and nanocrystalline materials used in current SSTs; thus thin GOES seems to be a good alternative to achieve a technological and economical balance by playing on both frequency and working induction levels to reduce the size of the transformer. The aim of the study is to assess the limits of the GOES use in terms of maximum operating frequency and flux density for power electronic like voltages, offering both high power density and efficiency in reduced volume. The primary and secondary windings of the transformer are respectively connected to standard electronic converters that deliver square shaped voltages. Losses under such regimes far from classical sinus cases have to be assessed. They are the root cause for heating of the device and shall be known before energizing the transformer. Experimental results and finiteelement simulation performed on the core structure, show that dynamic core losses are lower for square wave voltages than for sine waves at the same peak flux density and frequency. The maximum winding operating temperature obtained at thermal equilibrium fixes the operating limits of the device. Then to avoid issues due to eventual overheating when energizing the transformer, a thermal model suitable for predicting the temperature at various transformer locations has been developed and used; results are then described