Viviane Cristine Silva

A 3D finite-element computation of eddy currents and losses in the stator end laminations of large synchronous machines

Eddy current losses due to axial fluxes are computed in the stator end laminations of a salient-pole synchronous machine under open-circuit operating conditions. The calculation is carried out with the aid of a 3D finite-element package which uses a linear T-/spl phi/ formulation. The domain spans a full pole pitch of the machine. The flux densities computed in the end region at points outside the stator core are compared with experimental measurements. The results and the limitations of the model are discussed.

Determination of frequency dependent characteristics of substation grounding systems by vector finite element analysis

A three-dimensional finite-element tool was developed to compute time-harmonic electromagnetic fields and impedance of substation grounding systems. The formulation employs edge-based finite elements for the magnetic vector potential A and nodal shape functions for the electric scalar potential V. The method has been applied in several configurations presented in the literature. The results are compared with both analytical and experimental data reported by other authors, with overall good agreement

Efficient Parallel Preconditioned Conjugate Gradient Solver on GPU for FE Modeling of Electromagnetic Fields in Highly Dissipative Media

We present a performance analysis of a parallel implementation of preconditioned conjugate gradient solvers using graphic processing units with compute unified device architecture programming model. The solvers were optimized for the solution of sparse systems of equations arising from finite-element analysis of electromagnetic phenomena involved in the diffusion of underground currents in both steady state and under time-harmonic current excitation. We used both shifted incomplete Cholesky factorization and incomplete LU factorization as preconditioners. The results show a significant speedup using the graphics processing unit compared with a serial CPU implementation.

A new design technique based on a suitable choice of rotor geometrical parameters to maximize torque and power factor in synchronous reluctance motors. I. Theory

The influence of rotor geometry of synchronous reluctance motors (SRMs) on the x/sub d//x/sub q/ ratio, electromagnetic torque and iron losses is studied. Both air-gap length and rotor pole are are taken into account as parameters. First, a new theoretical approach is developed which neglects saturation effects (Part I). In a companion paper (Part II), a complete finite-element analysis of a particular SRM is carried out, followed by a comparison with results obtained by tests performed in a prototype machine, which was constructed in order to validate the proposed methodology.

Iterative Solution on GPU of Linear Systems Arising from the A-V Edge-FEA of Time-Harmonic Electromagnetic Phenomena

We present a performance analysis of a parallel implementation to both preconditioned Conjugate Gradient and preconditioned Bi-conjugate Gradient solvers using graphic processing units with CUDA programming model. The solvers were optimized for the solution of sparse systems of equations arising from Finite Element Analysis of electromagnetic phenomena involved in the diffusion of underground currents under time-harmonic current excitation. We used a shifted Incomplete Cholesky factorization as preconditioner. Results show a significant speedup by using the GPU compared to a serial CPU implementation.

A Wavelet-Based Algebraic Multigrid Preconditioning for Iterative Solvers in Finite-Element Analysis

A new approach for algebraic multigrid, based on wavelets, is presented as an efficient preconditioner for iterative solvers applied to the solution of linear systems issued from finite-element analysis. It can be applied to complex systems in which the coefficient matrix violates the M-matrix property, as those arising from ungauged edge-based AV finite-element formulation. When used as a preconditioner for the biconjugate gradient stabilized method it is shown that the proposed technique is more efficient than incomplete Cholesky preconditioner

Axial flux concentration technique applied to the design of permanent magnet motors: theoretical aspects and their numerical and experimental validation

Permanent magnet motors are widely used in drive technology. The use of ferrite magnets in this type of machine is attractive due to their low cost, but its performance is usually poor due to the low flux density in the airgap. A new topology for the magnetic circuit is proposed, which uses the concept of axial flux concentration. It enables a substantial increase in the flux per pole, even with ferrite magnets, thereby improving motor performance at a low cost. It is shown that the effect is equivalent to using a fictitious magnet material, with augmented remanence and recoil permeability. The proposed topology is applied in a prototype synchronous motor. The improvement in its performance is confirmed by both experimental procedure and finite element modeling in three dimensions

Efficient Modeling of Thin Wires in a Lossy Medium by Finite Elements Applied to Grounding Systems

A procedure is proposed to accurately model thin wires in lossy media by finite element analysis. It is based on the determination of a suitable element width in the vicinity of the wire, which strongly depends on the wire radius to yield accurate results. The approach is well adapted to the analysis of grounding systems. The numerical results of the application of finite element analysis with the suitably chosen element width are compared with both analytical results and those computed by a commercial package for the analysis of grounding systems, showing very good agreement.

Teaching electromagnetic fields and FEM for undergraduate students

An approach to the finite element method applied to the solution of electromagnetic fields problems is presented. This methodology is suitable for teaching electrical engineering students at undergraduate level, because the problem formulation is based solely on the direct integration of Maxwells equations and the approach is only valid for first-order elements, thereby avoiding the use of an excessively complex mathematical treatment.

Approach to teaching the finite element method applied to electromagnetic problems with axial symmetry to electrical engineering students

An approach to the finite element method applied to the solution of stationary electromagnetic problems with axial symmetry is presented. This method is suitable for teaching electrical engineering students at the undergraduate level. The problem formulation is based solely on the direct integration of Maxwells equations, and the approach is valid only for first‐order elements, thereby avoiding the use of an excessively complex mathematical treatment. Numerical examples illustrate the application of the proposed methodology to academic problems. Its validation is verified both by classical expressions of electromagnetic theory and by an educational finite‐element computer package.