Conference Agenda

Terahertz (THz) electrical signal generation from a photoactive semiconductor device illuminated by an optical pulse is modeled and simulated. Hydrodynamic equations in time domain are numerically solved using Discontinuous Galerkin Time Domain Finite Element Method (DGTD-FEM) for the high frequency charge transport that occurs in the semiconductor device. The obtained frequency spectra of various semiconductor materials under illumination of an ultrashort light pulse are presented. The inertia effects and ballistic transport of carriers play an important role to determine the frequency response of these materials, and the developed Hydrodynamic Model (HDM) solver delivers accurate results predicting higher frequency capabilities for GaAs and Ge detectors over Si-photodetectors. The HDM solver will be coupled with the full wave electromagnetic solver to simulate the comprehensive multiphysics scenario.

The electromagnetic induction heating is gaining more and more interest in the aeronautical field for the welding of thermoplastic composite materials, more precisely for the fixing of a stringer on a skin of fuselage. The presence of LSP (Lightning Strike Protection) on the underside of the skin is also considered. The LSP is a thin layer of copper covering the aircraft fuselage to ensure its protection against lightning. Its presence makes welding very complex because it concentrates most of the heating power and is therefore more strongly heated than the other parts. In this article the authors present a new technic to limit the heating of the LSP. A strongly coupled electrothermic 2-D finite element analysis is developed in order to optimize the temperature profile and to carry out the welding completed by 3-D modeling.

Non-inductive superconducting coils are being developed to create current-dependent nonlinear resistances. These resistances arethe basis of the operation of electric power devices such as fault-current limiters and superconducting power filters, for instance.For such applications, it is important to understand the behavior of the superconductor in both nominal and transient regimeswhich require their characterization in DC and AC as well as a combination of DC and AC (DC+AC). In the following work, aHigh Temperature Superconducting (HTS) non-inductive coil was first characterized via itsV-Icharacteristics in DC followed by anestimation of its losses as a function of the frequency and transport current in AC and DC+AC. A model of the losses based on theFinite Element Method (FEM) coupled with external electrical circuit was built using the open-source software Onelab. The resultsof simulations were compared to experimental data.

For the evaluation of stress-dependent magnetic properties of silicon steel, a principal stress decomposition method is examined and compared with the equivalent stress theory. A physical magnetization model called the multi-domain particle model simulates the stress dependence of the magnetic property by applying mechanical stress in directions different to the magnetic field direction. Experimental and computational tests show that the principal stress decomposition method gives a reasonable evaluation of stress-dependent properties.

Accurate simulation of magnetic hysteresis characteristics of electrical steel sheets under mechanical stress is the key step for the optimization design of iron cores for electrical equipment. Aiming at the defects of the existing methods, based on Energetic hysteresis model, a novel simulation method for magnetic hysteresis characteristics of electrical steel sheets under mechanical stress is proposed. Firstly, the energy density caused by mechanical stress as an additional term is introduced into the total energy density of electrical steel sheets. Then, the field separation technology is used to realize the conversion of energy density components to magnetic field components. Finally, according to the derivative of Helmholtz free energy of electrical steel sheets with respect to magnetization, the equation of stress additional magnetic field is derived, thus a magneto-mechanical hysteresis model of electrical steel sheets is established by using the field superposition principle. The results of simulation and measurement show that the proposed method has high precision.

The elliptic flux-line cutting model is extended beyond the critical state to describe the non-stationary magnetodynamics of a type-II superconductor subjected to a varying magnetic field. The Meissner currents, bulk pinning currents and flux cutting effects on the magnetic response of a rotating weak-pinning type-II superconductor, where the current density has perpendicular and parallel components to the magnetic field, is investigated. We perform numerical simulations to calculate the magnetic field in a type-II superconducting slab employing the method of lines and a second-order accurate spatial discretization based on a fixed set of nodes. For this system the numerical method is fast and accurate. We simulated experiments of an external rotating magnetic field parallel to the flat surfaces of the slab, comparing our simulations with experimental data a qualitatively agreement was achieved.

Energy based (EB) hysteresis models are thermodynamic consistent and show high potential for physically modeling ferromagnetic materials with high precision and have the capability to be implemented in Finite Element (FE) formulations with high efficiency. In this contribution, we review two EB hysteresis models and establish their equivalence, both, theoretically and numerically.

A novel approach to modelling and identification of selected nonlinear material characteristics is presented, based on stochastic processes. The approach is based on combination of artificial neural networks and continuous wavelet transform. The methodology is illustrated with determination of saturation curve of a transformer.

Electromagnetic fields and eddy currents in thin electrical steel laminations

are governed by the laws of magnetodynamics with hysteresis. If the lamination

is large with respect to its thickness, field and current distributions are

accurately resolved by solving a one-dimensional finite element magnetodynamic

problem across half the lamination thickness. This 1D model is then able to

deliver mesoscocpic information to be used, after appropriate homogenization,

in the macroscopic modelling of an electrical machine or transformer. As each

evaluation of such a homogenised model implies a finite element simulation at

the mesoscale, a monolithic implementation of this method can become very

time-consuming. This paper proposes an alternative methodology, assuming a

periodic excitation of the system, where the homogenized material law is

implemented with techniques of machine learning. The identified law is then

used as a conventional constitutive relationship in the 2D or 3D modelling of

an electrical machine or a transformer.

The excitation current of electrical equipment is distorted with harmonic components, which causes a significant increase in iron loss. A practical model is required to characterize the hysteresis loops of electrical steel excited with harmonic components. This paper exploits the static nonlinear hysteretic mechanics Bouc-Wen model to describe the domain wall motion process, and the model includes the resistance caused by the increase of domain wall energy and the hysteretic restoring force caused by material defects. The initial model is modified further by adding a new term that characterizes the rotation of domain. The dynamic model is built by considering the resistance caused by eddy current, then the high-order asymmetric loops under harmonic excitation are simulated. The frequency effect of the damping coefficient is considered. The comparison between the measured and calculated results validates the accuracy of the proposed model.

An integrodifferential model formulated in terms of the electric vector potential is developed for the 3D numerical modeling of the electromagnetic field in high temperature superconducting bulks, for AC losses evaluation. A matrix conditioning and the Newton Raphson method are applied to accelerate the convergence. The model is validated on a Benchmark. The comparison results show the accuracy of the model and its superiority in terms of calculation time compared to classical approaches.

A 1D magnetodynamic model for laminated steel is presented in this paper. In this model, the diffusion equation is solved across the lamination thickness. Because of the thin lamination thickness, the eddy currents at the lamination edge are disregarded without loss of accuracy. Thanks to this assumption the diffusion equation is reduced to two coupled 1D nonlinear partial differential equations. The average flux density across the lamination thickness is imposed on the problem as a boundary condition. A congruency-based vector hysteresis model is employed as the constitutive relationship. The excess field effect is included in the model through Bertotti’s empirical excess field equation. The governing equations are solved by a FEM toolbox. The developed model will be verified by comparing the simulation results with the experimental measurements.

This paper discusses the numerical implementation of an electro–quasistatic model that can be used to perform transient simulations of electric fields in HVDC cables insulation. With respect to the model traditionally employed, which describes a dielectric medium in terms of a constant permittivity and a temperature- and field-dependent electric conductivity, the presented one is extended with Debye’s equations for dielectric polarization processes. The model is implemented numerically using finite differences, or the Occhini equivalent circuit: this paper demonstrates that the two approaches are equivalent. Numerical simulations are presented to show the effect of polarization processes on the transient simulations.

To accurately calculate the core loss of transformers over broadband frequency range, an analytical expression of eddy current loss is obtained by solving Maxwell's equations considering skin effect. Furthermore, an improved field strength corresponding eddy current loss is proposed based on the equivalence of the loss separation and the field strength separation. An approximate real permeability is proposed based on the field strength corresponding to the excess loss so as to predict the loss and hysteresis characteristics of material in a wide frequency range. Based on the above disposal ,an improved dynamic hysteresis model whose accuracy and effectiveness is verified by comparing the predicted results with the measured ones under all kinds of working conditions is proposed.

We present a hierarchy of physical models for simulating the electric field transient in HVDC insulation during polarization and depolarization. The models are characterized byan increasing level of complexity which is required for capturing the effetcts of different phenomena wich become dominant in determining the electric field depending on the insulation material. We discuss numerical methods which are suitable for solving equations stemming from all models in the hierarchy and compare numerical simulation results to experimental measurements of insulator current during polarization ad depolarization transients.

This paper proposes an improved vector hysteresis model for integrating the impact of simultaneous rotating and DC-biased fields on vector B and vector H. In the proposed model, H components of the classical eddy current field and the anomalous field under the influence of DC-biased and rotating excitations are investigated separately for the more accurate analysis of the nonlinear relationship between vector B and vector H. A precise numerical analysis method for calculating magnetic quantities distribution of three-limb transformer core under AC and DC-biased excitations is developed by applying the proposed model into finite element method. The accuracy of the proposed method is proved by the close agreement between local B loci acquired experimentally and the calculated ones.