An original new method to better characterize ferrite materials used in power electronic applications

Today, linear properties of high frequency magnetic cores used in power electronics are exclusively stated by unique complex permeability, and the measurement of this variable is based on a magnetostatic approach. In MnZn ferrite cores, the grain insulation, which avoids the circulation of induced currents at low frequency, goes out of efficiency beyond about ten or a hundred kHz. Since eddy currents are able to circulate in these materials, by conduction or displacement of charges, usual reasoning is no more credible. A description closer to reality must also take complex permittivity into account. The purpose of this article is first to justify that both complex permeability and complex permittivity are necessary to accurately characterize ferrite materials, especially when frequency is growing up. The analytical model used to deduce these physical values is presented, and its validity domain is discussed. Experimental results are presented with this aim

Characterization of material versus temperature using P(VDF-TrFE) SAW transducers

This work approaches the elastic properties of non-piezoelectric materials and reports their temperature dependence for a duraluminum substrate. The method is based on the propagation time measurement of ultrasonic Rayleigh waves and attenuation of electrical voltage between emitter and receiver. Transducers made of P(VDF-TrFE) polymer film are used for Surface Acoustic Waves (SAW) generation and detectio

Equivalent circuits for transformers based on one-dimensional propagation: accounting for multilayer structure of windings and ferrite losses

International audienc

Des schémas équivalents pour les circuits couplés multi-enroulements

The aim of this paper is to represent the electrical behaviour of any number of magnetically coupled windings with couplers and inductors. Two methods, mathematicaly justified, are proposed. The second one introduces only positive inductances. As an exemple, it is applied to the representation of a three column three phase transformer. The obtained circuits supply the requisite guide to design more complete circuits which allow the high frequency behaviour of wound components to be taken into account, especialy in electronics simulation softwares.Le but de cet article est de traduire le comportement électrique d'un nombre quelconque d'enroulements magnétiquement couplés, par des coupleurs et des inductances. Deux méthodes, établies mathématiquement, sont proposées. La seconde n'introduit que des inductances positives. A titre d'exemple, elle est appliquée à la représentation d'un transformateur triphasé à trois colonnes. Les schémas obtenus fournissent l'indispensable ossature de schémas plus complets, aptes à représenter le comportement haute fréquence des composants bobinés, notamment dans un logiciel de simulation électronique

Using Confidence Factor to Improve Reliability of Wide Frequency Range Impedance Measurement. Application to H.F. Transformer Characterization

Abstract — Impedance analyzers are efficient in acquiring wide range impedance measurements in a wide frequency range. However, when measuring low impedances, short circuits used for compensation process can’t be considered as ideal and analogue problem appears for open circuit compensation. Fortunately, because impedance matrix of a two-port passive circuit is symmetrical, characterizing this circuit by four independent impedance measurements introduces redundancy. That property supplies a useful consistency test we call "confidence factor". Looking at this factor, several causes of measurement inaccuracy can be detected. Alternatively, extra equation supplied by redundancy can also be used to add one unknown impedance to the three computed. This way, impact of the impedance of a real imperfect short-circuit can be removed. In this paper, we first present the interest of the confidence facto