Search

We discuss numerical experiments to compare an isogeometric discretization of the electric field integral equation and a parametric Raviart–Thomas approach. Therein, we focus on accuracy with respect to degrees of freedom, briefly commenting on the conditioning of the system as well. Due to the utilization of parametric mappings even in the Raviart–Thomas approach, our investigation disregards any errors induced by meshing, which commonly favors the isogeometric approach when compared to curvilinear higher order Raviart–Thomas elements. [ABSTRACT FROM AUTHOR]

This paper deals with modeling and simulation of devices where current-carrying conductors are located close to magnetic bodies. These configurations typically occur in electromechanical energy converters such as in slots of electrical machines. Additional losses due to the inhomogeneous current density distribution (“current” or “field” diffusion) at high excitation frequency are a well-known phenomenon. However, classical approaches reach their limits as soon as field diffusion is influenced by ferromagnetic material with non-linear properties. An accurate but time-consuming computation can be achieved by using time-transient quasi-stationary finite-element analysis (FEA). Current diffusion can be described more efficiently by separating the conductor into parallel filaments, following the partial element equivalent circuit (PEEC) approach. As long as linear material characteristics are prevailing, the problem can, thus, be solved efficiently in the frequency domain. In this paper, a hybrid FEA-PEEC modeling approach is presented, where the magnetization of the ferromagnetic material is represented by equivalent currents obtained by 2-D FEA. It is suitable for complex multi-conductor configurations even including non-linear ferromagnetic material. For the proposed method, the resulting linear system is efficiently solvable in the frequency domain by direct solvers. A numerical example from the field of electric traction motors is presented to emphasize the accuracy and benefit of the proposed method for practical electromagnetic computations. [ABSTRACT FROM AUTHOR]

Time-domain finite element methods (FEM) are widely used for numerical solution of boundary value problems (BVP) arising from rotating electrical machines. Typically, the equations corresponding to discretizations of the rotor and the stator are solved simultaneously every time step, together with equations that couple them during rotation. We present a method for reformulating rotor and stator subproblems in time-domain BVPs into implicit Neumann boundary conditions determined by spectral Dirichlet-to-Neumann mappings. Thus, solution of the FE equations for the reformulated subproblem is no longer necessary every time step and significant reduction in solution time is often achieved. To demonstrate the effectiveness of the method, we discuss its application in two test cases. In the first test case, reformulated stator subproblem in a BVP for a squirrel-cage induction machine is coupled to an FE model of the rotor. In the second test case, both subproblems in a BVP for a synchronous reluctance motor are reformulated. Results are compared with those obtained with full two-dimensional transient FE analysis. [ABSTRACT FROM AUTHOR]

The validity of the flux rule to determine the electromotive force in a cycle, \cal E=-d\Phi/dt, has been the subject of a large amount of controversy since the beginning of electrical technology. Although most authors reach correct conclusions for a class of problems called Faraday paradoxes, the arguments that are used vary and often rely on ad-hoc physical reasoning. A didactic and insightful treatment should be based solely on Maxwell's equations, the constitutive laws, and a detailed study of the mathematics involved. [ABSTRACT FROM AUTHOR]

The classical Wilson–Wilson experiment in 1913 about the electromagnetic field in a rotating nonconducting cylinder is studied, based on finite-element analysis. Electric and magnetic fields are coupled through motional terms in the constitutive relations. This particular kind of coupling is usually not considered in the existing numerical models. Effects due to the finite axial extension of the cylinder can be conveniently assessed with the help of the finite-element simulation. This should be useful for the correct interpretation of the experimental data. [ABSTRACT FROM AUTHOR]

In high-speed solid-rotor induction machines, space harmonics in the air gap flux density corresponding to the stator slots typically cause significant losses on the rotor surface. Since these slot harmonics rotate very fast with respect to the rotor, their corresponding skin depths are typically very small. Loss estimates obtained by transient finite-element (FE) analysis may, therefore, require very fine spatial and temporal discretization and consequently very long solution time. In this paper, we derive a time-harmonic analytical model for the multilayer cylindrical rotor. Since the effect of the stator slots on the eddy-current losses cannot be ignored, the analytic solution is coupled to a numerical FE solution covering the stator. The resulting method is very fast since time stepping and meshing of the rotor can be avoided. The results are compared to those obtained with full 2-D transient FE analysis. [ABSTRACT FROM AUTHOR]

In this paper, we describe a general formalism that allows to reduce the spatial dimension of a field problem from 3-D to (2+1)-D. Subsequently, we identify conditions under which the third dimension can be eliminated. We see that the resulting 2-D field problems only decouple if an orthogonality criterion is fulfilled. The approach is based solely on differential-form calculus and can therefore be easily transferred into a discrete setting. As a numerical example, we compute the field of twisted wires. [ABSTRACT FROM AUTHOR]

We introduce a geometric formulation of the boundary element method (BEM), using concepts of the discrete electromagnetic theory. Geometric BEM is closely related to Galerkin-BEM and to the generalized collocation scheme. It is easy to implement, accurate, and computationally efficient. We validate our approach with 2-D examples and give an outlook to 3-D results. [ABSTRACT FROM AUTHOR]

Discrete electromagnetism (DEM)—in the authors' view-should be a self-consistent theory, mirroring the properties of the continuous electromagnetic theory in a discrete setting. Any recursion to continuous techniques can be interpreted as an inconsistency in the discrete theory. Recently, discrete Hodge operators on tetrahedra and triangles have been introduced that avoid the concepts of interpolation and integration of fields. In this paper we introduce a geometrical definition of a discrete Hodge operator for general dimension n and degree p, 0 ≤ n ≤ 3, 0 ≤ p ≤ n. The definition generalizes previously published definitions. The increased level of abstraction allows for a short definition and a concise discussion of the properties of this operator. [ABSTRACT FROM AUTHOR]

Electromagnetic problems can be solved using the coupled boundary-element-finite-element (BE-FE) method, where the conducting and magnetic parts are discretized by finite elements and the surrounding space is described with the help of the boundary element method. In this paper, we propose a novel BE-FE coupling procedure for the solution of electromagnetic problems. Starting from the potential formulation we derive a representation formula in the BE domain in terms of differential forms. We discretize the corresponding boundary integral equation by the DeRham map which generalizes the classical point collocation and yields an alternative approach to the Galerkin BE method. The Cauchy data will be discretized by the first-order Whitney elements on the boundary. In the FE domain, we apply the Galerkin discretization scheme using the spatial first-order Whitney elements. The coupling of these methods will be described and the feasibility of the proposed method will be demonstrated by means of numerical examples. [ABSTRACT FROM AUTHOR]

Deals with a study which applied fast methods in combination with boundary-element method-finite-element method coupling to nonlinear magnetostatic problems. Theoretical background and formulation; Numerical results; Conclusion.

Describes the parallel implementation of a preconditioned iterative solver based on coupling of a differential and integral approach. Information on parallel boundary- and finite-element methods; Computation of elemental matrices; Discussion on parallel coupling.

Provides information on a study which described the use of adaptive cross approximation technique in three-dimensional boundary element method (BEM). Approximation of matrix by vector products; Application of the BEM finite element method to solve electromagnetic and electromechanical problems; Methodology and results.

Presents electromagnetic field computation of superconducting magnets used for particle accelerators. Simulation of yoke using boundary element and finite element methods; Total magnetic scalar potential.

Presents a study about the numerical solution of two-dimensional eddy-current problems. Theoretical background; Presentation of the fast ferrite tuner to be optimized by numerical means; Performance of numerical simulations to judge the effects of slotting the strip line.

Presents information on a study which deals with the numerical analysis of electromechanical devices. Computation of forces; Coupling of electrical and mechanical system; Comparison of finite element and boundary element methods; Numerical example; Conclusions.

Focuses on a study that deals with the transient numerical analysis of electromechanical devices driven by thin wire coils using the finite element methods. Methodology; Numerical example; Conclusion.

Presents a study which summarized the theoretical background of three-dimensional eddy current problems with moving bodies using a Lagrangian description and boundary element method-finite element method (BEM-FEM) coupling. Fields and potentials; Application of BEM-FEM coupling; Numerical example.

Presents a novel iterative algorithm for the application of BEM-FEM coupling to nonlinear magnetic problems. Conventional algorithm; Novel algorithm; Numerical calculations of novel algorithm; Numerical examples.

Discusses the comparison of analytical and numerical integration techniques for the boundary integrals in the boundary element method-finite element method (BEM-FEM) coupling. The BEM-FEM coupling; Integration schemes; Numerical example; Conclusions.

Presents the use of coupling of finite elements and boundary elements to numerically treat a nondestructive testing (NDT) problem based on eddy currents. The BEM-FEM coupling method as used in solving the problem; Results of the application; Difficulties associated with the mesh; Difficulties associated with the receptive coils; Summary of the study.