Arnaud Bréard

Near Magnetic Field Coupling Prediction Using Equivalent Spherical Harmonic Sources

In the electromagnetic compatibility (EMC) behavior of power electronic converters, magnetic parasitic couplings between components are one of the main causes of dysfunctions or bad filtering (e.g., in EMC filter). These couplings could be as conducted or near-field interferences. In order to handle interaction problems, a complete knowledge of these magnetic couplings is then necessary. Our study is focused on near magnetic fields interferences. Indeed, the characterization of electromagnetic field in power electronics is still in active research. This paper details a predictive method that calculates accurately and efficiently the near magnetic field coupling between two sources. By using the near-field multipolar expansion in spherical harmonics of electromagnetic sources, the close magnetic coupling between two sources is determined from their equivalent model. It is shown that the increase in degree up to the fourth provides a more precise representation of the elements and thus a better accuracy of the near-field coupling prediction. Also, theoretical and experimental developments will be presented. The coupling between two complex sources will be considered to validate the predictive method.

Wide band measurements in time domain with current and voltage probes for power losses evaluation and EMC measurements on power converters

Current and voltage signal must be correctly measured in order to evaluate accurately power losses and electromagnetic interferences in time domain. This paper proposes a way to compensate the measured signals using the gain of the probes and an evaluation of the Common Mode Rejection Ratio of the differential voltage probe. Deconvolution shows its efficiency: the shape of the signal and the phase shift between current and voltage after compensation allow an accurate measurement of the power losses. Common Mode Rejection Ratio estimation shows that it is constant for the studied amplitude levels and there is low impact on the differential voltage measurements.

How to include frequency dependent complex permeability Into SPICE models to improve EMI filters design

Electromagnetic interference (EMI) filters design is a rather difficult task where engineers have to choose adequate magnetic materials, design the magnetic circuit and choose the size and number of turns. The final design must achieve the attenuation requirements (constraints) and has to be as compact as possible (goal). Alternating current (AC) analysis is a powerful tool to predict global impedance or attenuation of any filter. However, AC analysis are generally performed without taking into account the frequency-dependent complex permeability behaviour of soft magnetic materials. That’s why, we developed two frequency-dependent complex permeability models able to be included into SPICE models. After an identification process, the performances of each model are compared to measurements made on a realistic EMI filter prototype in common mode (CM) and differential mode (DM) to see the benefit of the approach. Simulation results are in good agreement with the measured ones especially in the middle frequen...

New Measurement System of Magnetic Near-Field With Multipolar Expansion Approach

In the electromagnetic compatibility (EMC) behavior of power electronic converters, it is important to predict the near-field coupling between the complex components (e.g., in EMC filter). Using the components of the near-field multipolar expansion of electromagnetic sources, the close magnetic coupling between two elements is determined from their equivalent model. In this paper, a new measurement system, based on spherical harmonics and spatial filtering, is proposed and studied. The sensor is a single coil moving along one axis, and coupled with a rotatable mount for the measured source with two axes of rotation θ and φ. This simple system, which can be easily automated, allows building good accuracy models for complex sources. The impact of the uncertainties in the position and orientation of the source and sensor is studied in order to determine the higher degree of the multipolar expansion that can be characterized. Taken into account these uncertainties and the expected precision of the reconstructed source, strategies of measurement minimizing the number of measurements are compared.