S.I. Nabeta

Mitigation of the Torque Ripple of a Switched Reluctance Motor Through a Multiobjective Optimization

The purpose of this work is to perform a multiobjective optimization in a 4:2 switched reluctance motor aiming both to maximize the mitigation of the torque ripple and to minimize the degradations of the starting and mean torques. To accomplish this task the Pareto Archived Evolution Strategy was implemented jointly with the Kriging Method, which acts as a surrogate function. The technique was applied on the optimization of some rotor geometrical parameters with the aid of finite element simulations to evaluate the approximation points for the Kriging model. The numerical results were compared to those from tests.

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

Assessment of the influences of the mutual inductances on switched reluctance machines performance

In the performance analysis of switched reluctance motors and generators, most authors neglect the effects of the mutual inductances between phases. However, mutual coupling influences the machine behavior in several ways. The aim of this paper is to discuss some of these aspects using simulation and tests results. This paper shows the simulation of a switched reluctance generator-SRG-with 3 phases, 6 stator poles and 4 rotor poles. Two simulation methods are discussed: the finite-element method coupled with circuit equations and the performance simulation using a Mathcad environment. The main features of both methods are discussed. The nature of the SRG power production is showed. The simulations and tests are conducted with the generator feeding a resistive load and constant rotor speed in the single pulse operating mode.

Finite element simulations of unbalanced faults in a synchronous machine

Two unbalanced faults (line-to-neutral and line-to-line short-circuits) in a synchronous machine are simulated by the finite element method (FEM). In order to accomplish these tasks, the FEM had to be associated with the moving-airband technique as well as the coupling with electric circuit. Results obtained in the simulations concerning the armature current and torque are compared with analytical curves.

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.

Finite element analysis of the skin-effect in damper bars of a synchronous machine

The skin-effect in the damper bars of a synchronous machine is analysed by a finite element simulation using SSFR (standstill frequency response test) data. In order to consider this effect in synchronous machine modelling, sub-subtransient parameters are introduced.

Design aspects of 4:2 pole-2 phase switched reluctance motors

Switched reluctance motors (SRM) are nowadays a well established choice for rugged and reliable variable speed drive applications. The 4:2 pole-2 phase configuration is particularly suited for low cost drives due to simpler motor construction and simpler driver topology with only two power switches. This solution has been proposed for fractional horsepower and relatively high speed applications like hand tools and light domestic appliances. In this paper some design aspects are treated, concerned with the SRM magnetic circuit. An analytical approach is first utilized for main geometric parameters definition and torque evaluation. In the sequence, a numerical approach utilizing finite element method is carried out to precise torque and inductance characteristics determination.

A fast algebraic multigrid preconditioned conjugate gradient solver

Abstract This work presents a new approach for selecting the coarse grids allowing a faster algebraic multigrid (AMG) preconditioned conjugate gradient solver. This approach is based on an appropriate choice of the parameter α considering the matrix density during the coarsening process which implies in a significant reduction in the matrix dimension at all AMG levels.

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

A Surrogate-Based Two-Level Genetic Algorithm Optimization Through Wavelet Transform

Despite the surrogate-based two-level algorithms that have been proposed for accelerating the optimization procedures, it may be still expensive for large problems. Therefore, this paper proposes the exploration of the approximation characteristics of the wavelet functions to define a coarse subspace for this kind of approach with relatively few float point operations. The wavelet transform is used to create the coarse model in a two-level genetic algorithm (GA), which is applied to a set of benchmark test problems. Although the coarse model is simpler and less accurate than the fine model, it behaves similarly to this last one and the original function. Moreover, the approach prevented the convergence to local minima whenever the GA presented such behavior and it is faster than the use of principal components analysis.