Stéphane Sire

Design and optimization of magnetic gears with arrangement and mechanical constraints for wind turbine applications

This article deals with the design and the optimization of magnetic and mechanical (structural) parts of magnetic gears for wind turbine applications. In particular, the design takes into account structural aspects of magnetic gears as well as mechanical constraints (deformation and stress) of the system. Geometric parameters are optimized in order to minimize the material cost for a 3.9 MW, 15 rpm wind turbine. This optimization includes magnetostatic and mechanical stationary finite element analyses. Optimization results show the necessity to take into account mechanical constraints particularly for the fixed ferromagnetic pole pieces.

Computation Time Analysis of the Magnetic Gear Analytical Model

This paper focuses on the computation time and precision of a linear 2-D magnetic gear analytical model. Two main models of magnetic gears are studied: 1) the first with an infinite relative permeability of yokes and 2) the second with a finite relative permeability of yokes. These models are based on the subdomain resolution of Laplace and Poisson equations. To accurately compute the magnetic field distribution, it is necessary to take into account certain harmonics of the various rings and other system harmonics due to modulation. Global system harmonics, which increase the value of computation time, must also be taken into account. If the magnetic gear has a high pole number, then computation time increases even more and no longer allows for system optimization. This paper proposes to compute magnetic field distribution using different harmonic selection methods in order to significantly reduce the computation time for the magnetic torque without any loss of accuracy.

Analysis of the dynamic behaviour of magnetic gear with nonlinear modelling for large wind turbines

This article deals with the dynamic behaviour of magnetic gear. This study is based on a nonlinear analytical model of magnetic gear which gives an analytical expression of the magnetic torque for a step disturbance. From this expression, various criteria will be defined in order to reach a good performance of the magnetic gear with step or sinusoidal disturbance. These results will be compared with a nonlinear simulation. Simulations show that it is possible to have, in a transitory regime, a load angle higher than the limit load angle maintaining a coupling between the low speed and the high speed rotor. Simulations will illustrate the importance of defining design rules based on the system application domain. A high power wind turbine (MW) example is proposed. In that case studies, loads generated by wind induce strong disturbances.

Analytical iron loss model for the optimization of magnetic gear

This article deals with analytical models dedicated to iron losses in yokes and pole pieces of a magnetic gear with a concentric structure. The magnetic field distribution is determined in yokes by solving both Poissons and Laplaces equations, whereas for pole pieces the magnetic field is computed by coupling the previous analytical model with a reluctance network model. The iron loss can then be determined in post-processing from the magnetic field analytical computation. The iron loss model used in this article takes into account the temporal and spatial variations of flux density. Results of this global analytical model permit to analyze the temporal and spatial evolution of flux density. In recognizing that the purpose of this model is to be integrated into a set of models for the global mechatronic optimization of magnetic gears, it is essential to minimize computation time. This work is being applied in the context of high-power (multi-MW) wind turbines.

Gear ratio optimization of a full magnetic indirect drive chain for wind turbine applications

This article deals with the optimization of a full magnetic indirect drive (FMID) with magnetic gears which uses an analytical model based on subdomain resolution of Laplaces and Poissons equations of the magnetic gear. A bi-objective analytical optimization is performed with a PSO algorithm with a minimization of the mass of the magnetic parts and a maximization of the gear ratio. This intermediate optimization is a step to optimize a 6MW FMID for a offshore wind turbine with one or two magnetic gears stages. It also compares FMID magnetic parts masses with a direct drive conversion chain with the same generator topology (hybrid excitation synchronous generator).

Supporting the Laminated Ferromagnetic Pole Pieces in a Magnetic Gear: A Structure Behaviour Analysis from a Multibody Model

This paper deals with the structure behaviour of a multi-bar system which maintains pole pieces in a magnetic gear. A simplified model of the system is proposed in order to be integrated in a multi-criteria global optimization for the sizing of a magnetic gear in wind power applications. For this purpose, the reduction of the computation time is taken into account. A geometry of the supporting bar is the defined and a Q bars structure is proposed. The study is based on a 1D model for each bar; variable radial and tangential magneto-mechanical pole pieces loads (generated by permanent magnets rings) are also considered. The resolution of the 6Q * 6Q system permits to determine quickly the evolution of displacements for each bar. An example of a magnetic gear with 151 pole pieces (i.e. 3,9 MW wind turbine) is proposed.

Behaviour Comparison Between Mechanical Epicyclic Gears and Magnetic Gears

This article deals with the magnetic gears with modulating ring and mechanical epicyclic gears and their operation. A power transmission analysis is done and permits to obtain an analogy of the kinematics between the two gear systems. Moreover, a transposition of the mechanical epicyclic gear arrangements to a magnetic gear arrangements can be made. Finally, a load repartition evolution description is proposed to complete the comparison between magnetic gears with modulating ring and mechanical epicyclic gears.

Enhanced Weld Penetrations In GTA Welding with Activating Fluxes Case studies: Plain Carbon & Stainless Steels, Titanium and Aluminum

Flux applications prior to the convention Gas Tungsten Arc Welding (GTAW) is known to improve weld penetrations and improve process competitiveness. This paper summarizes the investigations on aluminum, plain carbon steels, stainless steels and titanium. The importance of flux composition, homogeneity and profile of its application are shown to be primordial in determining the weld depth to width ratio of weld pools. The mechanisms that lead to improved penetrations along with some industrial case studies are presented.Key Words: ATIG, Weld penetrations, Steels, Titanium, Aluminum

A Self-Heating Approach to Characterize Anisotropy Effects in Fatigue Behaviour: Application to a Nineteenth Century Puddled Iron from a French Railway Bridge

The puddled iron is known for its extended use in monumental construction during the second half of the nineteenth century; among the structures built with such material are about half of French railway metallic bridges, most of them with over a century of service life. This scenario rises several concerns about the resistance of this material to cyclic loadings and therefore its fatigue behaviour. However, the puddled iron possesses several properties that make its mechanical characterization particularly difficult. Due to the puddling process this metal contains an important number of non-metallic inclusions that not only will turn out in a heterogeneous material but also (due to the rolling process) into an anisotropic one. In this paper a fast characterization of fatigue properties is proposed by using the self-heating method. The experimental self-heating curves obtained from specimens of the bridge of Toles (Chaumont, France) showed a scatter that was not observed in homogeneous materials (modern steel for example), this phenomenon is explained by the lack of determination of the representative elementary volume of the puddled iron. However, this data gives us important information such as the minimum and maximum boundaries of the mean fatigue limit for several orientations. An anisotropic two-scale probabilistic model for high cycle fatigue is also used to represent the orientation dependency of the results and the scatter found on the experimental data by using Hills elasto-plastic law and Weibulls distribution law to describe several characteristics of each site where the microplasticity occurs. The influence of such parameters and the limitations of the model are also discussed.