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This paper presents an original design option dedicated to output-filtered pulsewidth modulation inverters used in uninterruptible power systems, embedded networks, or motor drives operating on long cables. It is based on the coupling of interleaved inverter ceils by means of intercell transformers (ICTs) and is characterized by very good dynamic behavior on load transients, which is an important issue in such applications. ICT solutions are compared with the classical interleaved solutions using separate inductors. A specific design method is developed to achieve this comparison based on toroidal core shapes. The results obtained with a 600 V, 7.5 kW inverter show the usefulness of ICT-based designs, especially when nanocrystalline magnetic material is used; high specific power and very good dynamic performances are obtained. Index Terms--Embedded converters, intercell transformer (ICT), interleaved inverters, uninterruptible power system (UPS).

This paper presents the developments and the results of an analytic method elaborated to design isolated intercell transformers. These particular magnetic components are intended for multicell interleaved flyback converters recently proposed and well-suited to low-voltage, high-power applications. A specific 2-D model to evaluate the winding losses is included in the design process. The results, obtained for standard core shapes, allow defining the ranges of the main parameters, number of cells, and switching frequency, required for future realizations. Index Terms--Flyback converter, intercell transformer (ICT), interleaved converters, interphase transformers.

The theoretical advantage of InterCell Transformers over separate inductors is demonstrated in an interleaved power converter. Different practical ways to build InterCell Transformers are described. A theoretical approach dedicated to interleaved converters and InterCell Transformers analysis is presented. This analysis tool is used to understand and overcome the main drawback of InterCell Transformers. It is shown how the phase shifts between two adjacent phases must be modified to reduce the maximum flux density that influences core sizing and core losses. Index Terms--Coupled inductors, InterCell transformers, interleaved converters, interphase transformers.

An analytic formulation dedicated to the design of high-frequency power transformers is presented. This approach is based on the area product, and homothetic core shapes are considered. The temperature increase of the transformer is one of the main input data. Winding losses including the effect of eddy currents are calculated as well as core losses. An original model of magnetic losses valid over a wide frequency range of the common ferrite materials is introduced. The analytic formulation is validated by design examples concerning transformers that have been realized and tested. It is finally applied to study the evolution of power density versus operating frequency or power for different winding configurations or magnetic materials. Index Terms--AC resistance, winding losses.

An original converter composed of interleaved flyback is presented. The ceils are interconnected through intercell transformers replacing the standard multi-winding inductors used as insulation and storage magnetic device in the flyback. The combination of the interleaving effects and of the intercell transformer characteristics allows eliminating the mains limitations of the standard flyback due to the low performances of multiwindings inductors. In a first part, the different ways to interleave galvanic insulated converters as forward or flyback are briefly recalled. The second part presents the intercell transformers and shows that they can be used to interconnect interleaved converters cells. In the third and last part, this particular magnetic interconnection is applied to interleaved flyback cells and leads to create an 'intercell transformer flyback'. Its specific properties and advantages are described. Experimental results, obtained on a 2-kW test bench are finally presented. Index Terms--Coupled inductors, flyback, intercell transformer, interleaved converters, interphase transformers.

Interleaved power converters are now used in many different conversion systems involving various topologies (series or parallel) and related to different fields or loads. This paper deals with interleaved parallel commutation cells using coupling transformers with a possibly high number of cells. The first part of the paper is a reminder of the basics of magnetic couplers addressing monolithic as well as distributed implementations. The limits associated with the conventional supply of such couplers (supply voltages forming a direct polyphase system) are described. In the second part of the paper, an optimized voltage supply improving the performances of the system is introduced. Experimental results obtained on a seven-cells test bench validate the approach. Index Terms--Power converters, uninterruptible power supply (UPS) voltage regulator module (VRM).

This paper is focused on the design and the realization of two high-current probes (up to 100 A) whose bandwidths range from dc to 50 MHz. The performance has been met by the association of an active Hall sensor and a passive current transformer. This association will be named an 'active current transformer.' It will be shown that it has better frequency performance than the classical closed-loop current transducer, usually used for high-current measurements but frequency limited. The electromagnetic interference (EMI) issues, due to the sensor electrical environment are respected thanks to the shielded structure and special inner arrangements of the Hall sensors. Because of its large bandwidth, its large current range, and its EMI ruggedness, this current probe is well matched to power electronics measurements. Index Terms--Current probe, current transformer, electromagnetic interference (EMI), Hall sensor, power electronics.

In this article, a ferroelectric capacitor is characterized by an experimental Preisach density, determined by first order reversal curves method. It is experimentally shown that this density, does not allow a complete model of the ferroelectrical behavior. Considering the domain wall phenomenon, an extension of the Preisach assumptions is suggested.

This paper depicts a method to elaborate a high-frequency (100 kHz to 50 MHz) model of a current transformer. The method uses finite-element analysis to determine the values of the parameters of the circuit model; all electrostatic and magnetic couplings are taken into account and calculated. The paper shows how parasitic capacitance and flux leakage alter the transformer frequency response. These effects are deeply modified by the primary conductor position, by an air gap in the core, and by the presence of a shielding case around the transformer. The paper compares simulation results with experimental ones to show the accuracy of the models. Index Terms--Air gaps, current transformers, electromagnetic shielding, finite-element methods, high-frequency modeling.

Current measurements in power electronics or in EMI domains require high-performance probes. These probes must have a very wide bandwidth, be insensitive to electromagnetic interferences, and be able to measure large direct and alternating currents (ac-dc) without distortion. This paper will be limited to ac current probes. Various principles will be reviewed, in particular that based on the current transformer (CT); its limitations will be analyzed, and a solution based on a two-stage transformer will be proposed to extend low- and high-frequency performance. It will be shown that the use of new magnetic materials, such as the amorphous or the nanocrystalline, can improve large-current low-frequency operations, while preserving the smallest possible probe size. Various solutions will be provided to improve high-frequency operations. Different developments will be depicted; frequency and time-domain results will be presented. Index Terms - Amorphous magnetic materials, current measurements, current transformers, ferrite materials, HF transformers, magnetic tranducers, nanocristalline materials.

The induction heating appliances used for cooking generally include two or four inductors and in the most common solution, a converter is connected to each inductor. The main aim of this paper is to suggest a way of building a multi-load/single converter system, based on the use of a series-resonant ZVS inverter, supplying several resonant loads. The principle can be probably extended to different applications (dc-to-dc converters, high power induction heating applications) but our study has been restricted to a low power induction heating context. In order to make this study, suitable models for the loaded inductors had to be found. Therefore, in the first part of this document, a number of different electrical inductor models, from the basic L-R equivalent circuit to a representation taking into account eddy currents effects, are presented. The second part describes the multi-load operating principle with respecting ZVS conditions, by the analysis of an R-L inductor model. Finally, the third part completes this work with simulations, including a more realistic model of the inductors and the associated experimental validation. These emphasize the interest of this original system that is currently being evaluated for an industrial application. Index Terms--Induction heating, inductor modeling, multiload system, ZVS series-resonant inverter.

In this article a Preisach type density will be used to reconstruct the capacitive effects associated to a ferroelectric loop. This density will be experimentally determined using the FORC method. The small-signal capacitance, which can not be modelled by a Preisach type density, is measured simultaneously and must be subtracted from total capacitive effect. It will be shown finally that all ferroelectric loops, including minor loops, can be correctly reconstructed from this experimental Preisach density, on the condition that the small-signal capacitance is taken into account. [ABSTRACT FROM AUTHOR]