Loïc Rondot

An Energy-Compliant Magnetodynamic Error Criterion for Eddy-Current Calculations

In order to improve the finite element modeling of macroscopic eddy currents, a quadratic energy-based error criterion is obtained from a thermodynamic description of electromagnetism. Attention is first paid on the analytical derivation of the criterion in a general sense-i.e. without any assumption about the potential formulation and including possible body motion-especially to validate its relevance in 2D or 3D and to stress its independence from the formulation or the kind of application. Preliminary validation is given on a Thomsons effect device: As expected, the state functions provide the global convergence of the calculation within an iterative procedure whereas the conservation of the electromagnetic power is assessed locally to highlight the ill-checked elements.

3-D Magnetostatic Moment Method Dedicated to Arc Interruption Process Modeling

The behavior of arcs in circuit breakers is affected by interactions of several physics. To simulate this, a 3-D modeling system has already been developed. It considers the arc fluid dynamics, the radiation, the plastic vaporization, the current flow within the electrodes and the plasma, and the magnetic field generated by currents. However, to consider the influence of ferromagnetic regions, the current simulation model has to be extended. The magnetic moment method (MoM) is an integral method where only active regions (i.e., ferromagnetic regions in our context) are meshed. Thus, it is particularly well adapted for breaking modeling with a few ferromagnetic regions in comparison with the whole air region. In this paper, circuit breaker principle is explained, the arc interruption modeling is described, a nonlinear MoM model based on a point matching approach is discussed, and finally an arc interruption process modeled with the introduction of ferromagnetic regions is presented.

A Hybrid Boundary Element Method-Reluctance Network Method for Open Boundary 3-D Nonlinear Problems

A scalar potential formulation coupling a hybrid boundary element method and a reluctance network method is presented to solve 3-D nonlinear magnetostatic problems. The computation times and the accuracy of this approach are compared with those of the finite element method in the context of force and torque evaluations. It is shown that this method could efficiently be used for the presizing of actuators. Discussion concerning the advantages of this approach compared to a pure reluctance network method is also presented.

Enhancing Quasi-Static Modeling: A Claim for Electric Field Computation

Although electric field seems useless in non-conducting regions depicted within the quasi-static magnetic regime, its calculation appears necessary therein to: (i) improve the mesh quality required by eddy-current computation; and (ii) tackle the interplay between power transmission and its loss of integrity induced by higher frequencies. The discussion lies on a thermodynamic-oriented description of electromagnetism and a reversible interpretation of the Faradays law. Energy efficiency challenges deserve such an attention.

3-D Hybrid FEM–BEM Using Whitney Facet Elements and Independent Loops

This paper presents a hybrid formulation using Whitney facet elements. This formulation is efficient for the modeling of unbounded 3-D magnetostatic problems. Boundary element method is used to model the unbounded regions and finite element method to model the ferromagnetic ones. Using equivalent circuit representation, the problem is changed, the degrees of freedom becoming magnetic flux in loops instead of faces. As a result, the dimension of the system to be solved is decreased.

Assessing anomalous losses with dynamic hysteresis models

A new approach to face the problem of dynamic hysteresis and assess extra-losses in soft magnetic materials is investigated. Thanks to a spatial averaging technique and a variational principle, a dedicated formulation is derived. It takes into account microscopic magnetization mechanisms and domain wall motion-induced Joule losses. A validation is proposed by assessing time-harmonic losses on a 2D-Pry and Bean iron sheet. Discussion includes also a confrontation with the delayed diffusion model and Bertottis experiments.

A Magnetodynamic Error Criterion and an Adaptive Meshing Strategy for Eddy Current Evaluation

In order to address their considerable impacts on both the energy efficiency and performance requirements, eddy current modeling and its accuracy are discussed from a thermodynamic approach. An energy-based error criterion for automatic mesh adaption is developed. Coupled with a remeshing strategy that preserves mesh quality, some numerical results are given on an induction machine.

From Galilean Covariance to Maxwell Equations: Back to the Quasi-Static Regimes

Galilean electromagnetism is derived from a thermodynamic approach. Attention is paid on various regimes allowed by the quasi-static limit. It is emphasized that classical definition of electro-quasi-stationary and magneto-quasi-static regimes does not cover all the low-frequency case studies. As suggested by the thermodynamic approach of electromagnetism, it is proposed to: 1) discuss the validity of the regimes at the device scale and 2) derive the set of equations underlying the regimes from the variations of the magnetic and electrostatic powers instead of the magnitudes of the magnetic flux density and the electric field.

From Galilean covariance to gauge conditions: A thermodynamic insight to signal integrity

In order to address the signal integrity issue, Galilean electromagnetism is derived from a thermodynamic approach. Attention is paid on the various regimes allowed by the quasi-static limit. It is emphasized that an abrupt transition exists between the QS-magnetic and the QS-electric regimes for which different gauge conditions on the potentials should be considered.

Electric Field Computation in Nonconducting Regions Using A-V After a

This paper presents a model of electric field calculation in nonconducting regions in steady state AC magnetic application, with conductors described by surface impedance, using the 3-D finite element method. This approach is validated by calculating the equivalent impedance of a coil comparing the presented surface impedance decoupled method with a volume decoupled method.