H. Ben Ahmed

3-D Formal Resolution of Maxwell Equations for the Computation of the No-Load Flux in an Axial Flux Permanent-Magnet Synchronous Machine

This paper presents a 3-D analytical model of an axial flux permanent-magnet synchronous machine, based on formal resolution of Maxwell equations. This method requires much less computation time than conventional 3-D finite elements, and is therefore suitable for optimization purposes. In a first part, the mathematical procedure used to compute the machine no-load flux is described in detail. This method is 3-D, and then takes into account the radial edge effects of the machine, as well as the curvature effects by a resolution in cylindrical coordinates. Moreover, the originality of this method lies in the fact that it is totally analytical. The obtained results are verified using 3-D finite elements, and compared with simpler analytical models of axial flux machines, taken from the literature. This work puts in evidence the advantages of the proposed model. In particular, it is shown that the radial edge effects are important for a correct estimation of the no-load flux. On the contrary, the curvature effects are a second-order phenomenon.

Piezoelectric Actuator Design and Placement for Switched Reluctance Motors Active Damping

This paper describes the design and the placement of piezoelectric actuators on switched reluctance motors by means of a genetic algorithm (nondominated sorting genetic algorithm II) for the purpose of reducing stator vibrations. Two distinct approaches are presented: one energy-related and the other based on a minimization of the resultant displacement. These methods lead to design and placement strategy for the piezoelectric actuators. A number of optimal actuators obtained using these kinds of approaches is also compared with mechanical finite-element simulations. At last, a solution is achieved in order to validate optimal placement using positive position feedback active filtering.

Loss separation in soft magnetic composites

We report and discuss significant results on the magnetic losses and their frequency dependence in soft magnetic composites. Two types of bonded Fe-based materials have been characterized at different inductions from dc to 10 kHz and analyzed by extending the concept of loss separation and the related statistical theory to the case of heterogeneous materials. Starting from the experimental evidence of eddy current confinement inside the individual particles, the classical loss component is calculated for given particle size distribution. Taking then into account the contribution of the experimentally determined quasistatic (hysteresis) loss, the excess loss component is obtained and quantitatively assessed. Its behavior shows that the dynamic homogenization of the magnetization process with frequency, a landmark feature of magnetic laminations, is restrained in these materials. This results into a partial offset of the loss advantage offered by the eddy current confinement.

Three-Dimensional Analytical Modeling of a Permanent-Magnet Linear Actuator With Circular Magnets

We describe a 3-D analytical model based on formal resolution of Maxwells equations of a permanent-magnet linear actuator, with circular-shaped magnets. We present all details of the 3-D analytical calculation for the no-load flux and then compare results obtained by this model to those obtained by 3-D finite-element analysis. The comparisons show a good agreement between the two models and so validate our analytical model. Unlike 3-D finite-element analyses, which are time consuming, the analytical models that we present in this paper are suitable for an optimization process of such a structure.

An Analytical Model for the Computation of No-Load Eddy-Current Losses in the Rotor of a Permanent Magnet Synchronous Machine

This paper describes an analytical model for computing the rotor eddy-current losses in the case of permanent magnet synchronous machines, based on a formal resolution of Maxwells equations. We focus on the computation of the eddy currents in the machine magnets, in which the diffusion equation is analytically solved, using an accurate electromagnetic model of the stator slotting. The model originality lies in its capacity of taking into account both the diffusion phenomenon and the magnets finite length over the pole pitch, imposing that the total current over the magnets surface should be zero at each instant. This important problem is studied by solving a Fredholm integral equation. A validation using a 2-D time-stepping finite-element model is also performed, and the obtained losses are shown to be in good agreement with those given by the analytical method, for a shorter computation time.

Bi-objective sizing optimization of a PM machine drive on an operating profile

This article sets forth a design optimization methodology for an SMPM machine drive on an operating profile. The optimization parameters serve to describe both the machine geometry and electrical ratings of the electronic power converter. Each operating point is treated independently, and current control is optimized at every operating point in order to not only minimize machine drive losses but also satisfy a number of constraints. This optimization methodology will then be applied to the design of a direct-drive conversion chain for a wave energy converter (WEC).

Design of electromagnetic actuators using optimizing material distribution methods

This paper deals with the design of electromagnetic actuators via topology optimization methods. It focuses on the development of an optimizing material distribution tool based on a genetic algorithm, the NSGA-II. The originality of this tool is to use a material distribution formalism based on Voronoi cells and to allow not only the material, but also the number and position of these cells to be parameters of the optimization. The application of the method to two practical cases, a linear actuator and a ferrofluid-based micropump, reflects the interest and the potentialities of the method in general, and of the distribution formalism particularly. Some experimental results also confirm the quality of the solutions produced by the design tool.

Extended frequency analysis of magnetic losses under rotating induction in soft magnetic composites

We present novel results on magnetic losses in soft magnetic composites (SMCs) excited with rotating field. Soft composites are very promising in electrical engineering applications, where new topologies of electrical machines with two- and three-dimensional induction loci are increasingly found. An experimental characterization of industrial SMC products has, therefore, been carried out, up to the kilohertz range, under alternating and circular flux loci, making use of a specifically designed and optimized loss measuring setup. The obtained results have been analyzed for all kinds of excitation, according to the loss separation concept, with the emphasis being placed on the relationship between the rotational and the alternating loss components. In particular, it is found that the ratio between the rotational and the alternating losses is, for any given peak induction, independent of frequency.

Genetic algorithm-based topology optimization: Performance improvement through dynamic evolution of the population size

Topological optimization tool using genetic algorithm as optimization algorithm are known as very expensive in computation time. In this paper, we study an approach to improve performance of topological optimization tool by introducing a dynamic variation of the population size of children during the process of optimization. This method allows to improve performance of each generation by adapting the number of children created and by introducing a coefficient of reproduction for each individual inside the population of parents. Through this coefficient of reproduction, the number of children assigns to each parent is calculated. The number of evaluations at each generation changes and the tool can saves evaluations in order to increase the number of iterations.

3D Analytical Model for a Tubular Linear Induction Generator in a Stirling cogeneration system

This article sets forth a 3D analytical model of a tubular linear induction generator. In the intended application, the slot and edge effects as well as induced current penetration phenomena within the solid mover cannot be overlooked. Moreover, generator optimization within the present context of cogeneration has necessitated a systemic strategy. Reliance upon an analytical modeling approach that incorporates the array of typically-neglected phenomena has proven essential to offering greater computational and analytical flexibility. This article will describe the electromagnetic model of the generator and draw comparisons with a finite element model, in addition to identifying the elements of equivalent electrical diagram and displaying results from the multi-objective optimization study performed using a genetic algorithm.