42 research outputs found

    Perturbation Finite Element Method for Efficient Copper Losses Calculation in Switched Reluctance Machines

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    Copper losses dissipated in the windings of electric machines are the sum of classical ohmic dc losses and additional ac eddy current losses. In fact, the level of eddy current losses is strongly correlated with the manner of disposition of coil conductors in machine slots. Then, to improve the efficiency in electric machines, the selection of an optimal winding configuration becomes substantial. Since eddy current losses derive from the strong electromagnetic coupling between current density and time-dependent magnetic field, which cannot be solved easily, numerical analyses, such as particularly the one using the finite element (FE) method, are often used. As for the FE modeling, it can employ moving band technique to perform the rotor motion and Newton-Raphson iterations to deal with the nonlinear behavior of magnetic circuits. It leads then to a substantial computational time that hinders any process of conception or optimization of winding geometries. To overcome this issue, a 2-D FE model reduction based on the perturbation method is proposed. It starts from one approximate FE solution of a simplified complete machine modeling to find fast but accurate solutions in slots subdomains when any variation of geometrical or physical data occurs. It allows adapting nonconforming meshes and provides clear advantages in repetitive analyses when we search the optimized winding configuration for a given number of turns. © 1965-2012 IEEE

    3-D modeling of heterogeneous and anisotropic superconducting media

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    In this paper, we investigate the 3-D computation of the current distribution in the heterogeneous superconducting media with a discontinuous anisotropic E - J constitutive power law. The resulting 3-D vectorial non-linear diffusion problem satisfied by the electric field is solved in each region of the media with a discontinuous Galerkin method combined with a 3-D semi-implicit scheme recently proposed for the 3-D modeling of homogeneous bulk superconductors. Numerical applications on the media consisting of two embedded anisotropic superconducting regions with and without a conductive matrix are computed. Both critical current density J-{c} and power law exponent n are uniform in each region but discontinuous in the media. The results will show the continuity of the diffusion phenomena in the media and the differences between both isotropic and anisotropic cases under an applied axial sinusoidal magnetic field

    Numerical study of the influence of flux creep and of thermal effect on dynamic behaviour of magnetic levitation systems with a high- superconductor using control volume method

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    ID = 326International audienceThis paper displays some simulation results of dynamic responses of the high- superconductors (HTSC)-Permanent magnet (PM) levitation systems taking into account the influence of the flux creep phenomena and of the thermal effect. We focus on the establishment of a three-dimensional numerical code to solve the nonlinear and coupled equations. A new control volume method is proposed for the resolution of the partial derivative equations of the treaded physical phenomena. The influence is comprehensively displayed by comparing the predictions of dynamic responses of such systems in which the thermal effect in the superconductor is and is not taken into account. The electromagnetic and thermal coupling is ensured by an alternate algorithm. The thermal effect highlights the influence of the temperature on the value of the magnetic levitation force, levitation stabilization time and shows that the vibration center of levitated body had drifted downward

    Modeling of a beam structure with piezoelectric materials: introduction to SSD techniques

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    International audiencePurpose‚Äď To provide a model that allows testing and understanding special damping techniques.Design/methodology/approach‚Äď The finite element modeling takes into account the piezoelectric coupling. It is used with a non linear electrical circuit. The approach leads to an accurate tool to observe the behavior of the non linear damping techniques such as synchronized switch damping.Findings‚Äď The model has been validated by comparison with Ansys¬ģ but the CPU time required for the model is around one hundred times shorter.Research limitations/implications‚Äď The proposed model is 1D and the assumptions to use it are not verified for all structures.Practical implications‚Äď The authors obtain a useful tool for the design of damping structures (for example to find the best localisation of the piezoelectric patches and to test electrical circuits).Originality/value‚Äď The model is used for the design and conception of damping as well as for harvesting structures

    Analysis of electromagnetic strains on a structure such as switched reluctance machine

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    In this paper, a coupled magneto-mechanical finite-element model is briefly presented and then used to determine the different electromagnetical strains of a structure mechanically closed to a single-phase stator of a switched reluctance motor. Magnitudes of the magnetostrictive forces and of the magnetic forces, such as their relative importance in the structure strain, are given for different current excitations

    Magnetization Modeling of Twisted Superconducting Filaments

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    This paper presents a new Finite Element numerical method to analyze the coupling between twisted filaments in a superconducting multifilament composite wire. To avoid the large number of elements required by a 3D code, the proposed method makes use of the energy balance principle in a 2D code. The relationship between superconductor critical current density and local magnetic flux density is implemented in the program for the Bean and modified Kim models. The modeled wire is made up of six filaments twisted together and embedded in a lowresistivity matrix. Computations of magnetization cycle and of the electric field pattern have been performed for various twist pitch values in the case of a pure copper matrix. The results confirm that the maximum magnetization depends on the matrix conductivity, the superconductor critical current density, the applied field frequency, and the filament twist pitch. The simulations also lead to a practical criterion for wire design that can be used to assess whether or not the filaments are coupled