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Research – Development – Innovation

PhD defense – Carlos Cuellar

TitleHF characterization and modeling of magnetic materials for the passive components design of EMI filters

Date : Monday October 7th, 2013
Time : 10h30
Location : IUT A de Lille – Cité Scientifique

Abstract :
The switching semiconductor devices in static-converters are the main source of electromagnetic interference (EMI). Reduction of these emissions can be achieved by different techniques including the use of EMI filters which design requires the use of magnetic cores. These must have adequate physical properties allowing the EMI filter to fulfil its task within a specified frequency range whatever the operating conditions (saturation, temperature…). Therefore, in the present work, some methodologies and models are developed in order to be able to design the EMI filter within its real conditions of operation.
First, the magnetic core is considered in small-signal conditions and a method is proposed to measure the complex magnetic permeability in high frequency (HF). Two models, analytical and lumped-circuit network, are developed to account for the HF characteristics. In a second step, the material is considered saturable as the EMI filter can be subjected to more important currents, leading to the modification of its main characteristics. Then, a non-linear modelling approach, with and without hysteresis effect, including a material capacitance is considered for modelling the magnetic core. Additionally, a technique is proposed to characterize in HF the magnetic hysteresis loop from a single turn flat coil configuration.
Finally, an improved current injection method, with new designed current probes, is used to characterize the input impedance of a converter. The impedance, combined with the developed small-signal and high-signal material models, is used to predict the insertion loss of an EMI filter. Simulation results are validated by the experiment.