M. Repetto

Stochastic algorithms in electromagnetic optimization

This paper gives an overview of some stochastic optimization strategies, namely, evolution strategies, genetic algorithms, and simulated annealing, and how these methods can be applied to problems in electrical engineering. Since these methods usually require a careful tuning of the parameters which control the behavior of the strategies (strategy parameters), significant features of the algorithms implemented by the authors are presented. An analytical comparison among them is performed. Finally, results are discussed on three optimization problems.

Multiobjective optimization in magnetostatics: a proposal for benchmark problems

A proposal for benchmark problems to test electromagnetic optimization methods, relevant to multiobjective optimization of a solenoidal superconducting magnetic energy storage with active and passive shielding is presented. The system has been optimized by means of different optimization procedures based on the global search algorithm, evolution strategies, simulated annealing and the conjugate gradient method, all coupled to integral or finite element codes. A comparison of results is performed and the features of the problem as a test of optimization procedures are discussed.

Modeling of electromagnetic phenomena in soft magnetic materials under unidirectional time periodic flux excitations

We report on recent advances in the modeling of magnetic losses in steel laminations used in electromagnetic devices. The integrated-lamination moving dynamic Preisach model, used to evaluate the dynamic magnetization loops under distorted unidirectional flux patterns, is described. The main goal is the comparison of two numerical procedures, using the finite element-finite difference technique and the finite element-fixed point technique, respectively, each properly taking into account the hysteresis characteristics by the Preisach theory. Moreover, attention is paid to the identification of the material parameters entering the moving dynamic Preisach model. Finally, the two techniques are validated by the comparison of numerical experiments and measurements on two different materials. Here, global as well as local quantities in the lamination structure are evaluated.

SMES Optimization Benchmark Extended: Introducing Pareto Optimal Solutions Into TEAM22

In 1996, a superconducting magnetic energy storage arrangement was selected to become a benchmark problem for testing different optimization algorithms, both deterministic and stochastic ones. Since the forward problem can be solved semianalytically by Biot-Savarts law, this benchmark became quite popular. Nevertheless, the demands on optimization software have increased dramatically since then. To give an example, methods looking for Pareto-optimal points rather than for a single solution only have been introduced by several groups. In this paper, a proposal for an extended version of the benchmark problem will be made and some results will be presented.

Analysis of isotropic materials with vector hysteresis

This paper presents the implementation of an isotropic vector hysteresis model within a two dimensional time periodic finite element procedure, formulated in terms of magnetic vector potential. The standard vector Preisach Model is employed and an identification procedure based on the scalar Preisach distribution function is used. Nonlinearity is handled by means of the fixed point technique following the H-convergence scheme. The convergence of the procedure is assessed and the results obtained are discussed.

A hysteretic periodic magnetic field solution using Preisach model and Fixed Point technique

The paper presents a computational approach for periodic magnetic field problems including hysteresis. The procedure is based on the finite element method combining scalar Preisach model with Fixed Point technique. The computational scheme is applied to a one-dimensional model problem. The results are validated by comparison with the exact analytical solution.

Loss separation analysis in ferromagnetic sheets under PWM inverter supply

A Finite Element model is used to investigate the influence of different PWM parameters on iron loss components. It is found that only the classical losses are sensibly affected by the supply waveform. The predictions are validated by the experiments. Finally, a comparison with an analytical approach is presented.

Computation and measurement of iron losses under PWM supply conditions

The paper presents a method for the estimation of the iron losses under PWM (Pulse Width Modulation) flux supply conditions. The computational results are validated versus measurements on Epsteins yoke. The proposed model is based on Finite Element method formulated in the harmonic domain and takes into account ferromagnetic hysteresis and eddy currents. A classical Preisach model is used for hysteresis modelling neglecting the effects of excess losses in field analysis. Different PWM supply conditions are measured and simulated with satisfactory agreement.

Dual-PEEC Modeling of a Two-Port TEM Cell for VHF Applications

Two-port TEM cells with rectangular cross section are commonly used to produce plane electromagnetic waves with high electric field. The non-uniform structure makes the use of numerical methods extremely useful in the design phase in order to achieve a very good behavior of the TEM cell over a wide frequency range of operation. In this paper an extended version of PEEC is used to study a real device and results are compared with experimental ones.

An Advanced Electromagnetic Code For The Analysis And Design Of Electromechanical Apparatuses

The paper presents the features of a two-dimensional code for electromagnetic field analysis. The structure of the code, based on a hybrid Finite Element Boundary Element field formulation, is outlined with particular reference to its characteristic features. Some examples of application of the code to the analysis of different electromagnetic devices are finally shown and discussed.