A New High-Current Large-Bandwidth DC Active Current Probe for Power Electronics Measurements

International audienceThis 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

Characterization and model of ferroelectrics based on experimental Preisach density

In this article an experimental method of characterization and modeling of ferroelectric materials is presented. The reversible and irreversible contributions of polarization are separated. The measurements of these effects are performed simultaneously giving a perfect separation. Investigations on switching behavior under different electric field strengths permit final representation of totally irreversible effects by a two-dimensional (2D) function. This function, a Preisach-type density, allows us to extract traditional information such as remanent polarization, coercive field and so on. Then, this curve is fitted to a 2D Gaussian distribution in order to provide easy implementation in simulators. Finally, a physical model is considered to interpret this experimental function in terms of switching mechanism, leading to a powerful tool for future investigation, e.g., the origin of aging. (C) 2002 American Institute of Physics

High-frequency modeling of a current transformer by finite-element simulation

International audienceThis 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

Autologous hematopoietic stem cell transplantation for intravascular large B-cell lymphoma: the European Society for Blood and Marrow Transplantation experience.

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