Near Magnetic Field Coupling Prediction Using Equivalent Spherical Harmonic Sources

Abstract

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 field's 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.Index Terms-Electromagnetic compatibility (EMC), near magnetic field coupling, power electronic, spherical harmonic.

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

“…Table 1. shows the mean relative error µ for each coefficient of the multipolar expansion of a smoothing inductor [2]: Q 10 = 6.8e-2; Q 20 = 4.43e-4; Q 30 = -7.94e-5; Q 40 = -2.18e-5 as a function of the number of measurements N evenly distributed over a cylinder or over a half cylinder. 2.9e -3 2e -1 1.7e -1 3.4e -2 1.9e -4 9.2e -3 8.9e -3 5.9e -3 20 2.5e -3 1.7e -1 1.4e -1 2.8e -2 1.4e -4 7.2e -3 7.1e -3 4.8e -3 The magnetic flux is first computed for each component at each equivalent position of the sensor over a sphere (see fig.…”

“…This element is represented by an equivalent punctual source composed of components of a multipolar expansion, which allows calculating the near-field coupling with other radiating elements [1]. In a previous work, a measurement method was developed to determine the zero-order components of the first four degrees of the multipolar expansion (Q i0 , i=1,4) [2]. In [3], a complete coil set (composed of both zero-and non-zeroorder components) for multipolar expansion identification was presented, but the study stopped at second degree and no experimental validation has been done for the non-zero-order components.…”

Error analysis for near-field EMC problems based on multipolar expansion approach

“…In the previous work [1], a measurement method was only developed to determine the zero-order components of the first four degrees of the multipolar expansion (N max = 4), which is exclusively limited to axially symmetric sources.…”

“…However, EMC problems are currently treated after the production of a prototype, which causes additional costs and significant delays if the needed standards are not reached. In order to consider the compliance to EMC standards from the very beginning of the design phase, a method has been developed at Laboratoire Ampère [1] to predict near-field coupling between complex components. This predictive method is based on the multipolar expansion of the radiation in spherical harmonics on a field close to the element.…”

“…Error analysis for near-field EMC problems based on multipolar expansion approach Z.Li 1 , F.Tavernier 1 ,A.Bréard 1 ,L.Krähenbühl 1 and D.Voyer 1 1 Université de Lyon -Ampère (CNRS AMR5005) ,ECL, 69134Écully, France zhao.li@doctorant.ec-lyon.fr…”