Computer-aided modeling and prediction of performance of the modified Lundell class of alternators in space station solar dynamic power systems

The main purpose of this project is the development of computer-aided models for purposes of studying the effects of various design changes on the parameters and performance characteristics of the modified Lundell class of alternators (MLA) as components of a solar dynamic power system supplying electric energy needs in the forthcoming space station. Key to this modeling effort is the computation of magnetic field distribution in MLAs. Since the nature of the magnetic field is three-dimensional, the first step in the investigation was to apply the finite element method to discretize volume, using the tetrahedron as the basic 3-D element. Details of the stator 3-D finite element grid are given. A preliminary look at the early stage of a 3-D rotor grid is presented

On the Uniqueness of Solution of Magnetostatic Vector‐potential Problems by Three‐dimensional Finite‐element Methods

In this paper, particular attention is paid to the impact of finite‐element approximation on uniqueness and to approximations implicit in finite element formulations from the uniqueness requirements standpoint. It is also shown that the flux density is unique without qualifications. The theoretical and numerical uniqueness of the magnetic vector potential in three‐dimensional problems is also given. This analysis is restricted to linear, isotropic media with Dirichlet Boundary conditions. As an interesting consequence of this analysis it is shown that, under usual conditions adopted in obtaining three‐dimensional finite‐element solutions, it is not necessary to specify div Ā in order that Ā be uniquely defined

Analysis of electromagnetic interference from power system processing and transmission components for Space Station Freedom

The goal is to analyze the potential effects of electromagnetic interference (EMI) originating from power system processing and transmission components for Space Station Freedom.The approach consists of four steps: (1) develop analytical tools (models and computer programs); (2) conduct parameterization studies; (3) predict the global space station EMI environment; and (4) provide a basis for modification of EMI standards

Analysis of electromagnetic interference from power system processing and transmission components for Space Station Freedom

The goal of this research project was to analyze the potential effects of electromagnetic interference (EMI) originating from power system processing and transmission components for Space Station Freedom. The approach consists of four steps: (1) developing analytical tools (models and computer programs); (2) conducting parameterization (what if?) studies; (3) predicting the global space station EMI environment; and (4) providing a basis for modification of EMI standards

An Extremely Fast Technique for Nonlinear Three Dimensional Finite Element Magnetic Field Computations

A fast Newton-Raphson technique (FNR) for the determination of nonlinear three dimensional finite element magnetic fields in electrical devices is presented. The new technique provided substantial reduction in CPU time required for complete and converged nonlinear magnetic field solutions by more than 50% in comparison with the standard Newton-Raphson (NR) Technique. The significant reduction in CPU time was achieved without any sacrifice in the accuracy of the converged three dimensional magnetic field solutions or in the values of the device terminal parameters. To illustrate the great advantages of the new method, an example single phase transformer was implemented with widely varying degrees of magnetic saturation. Values of magnetic vector potential, as well as flux density components, obtained using the new technique, were compared with the values obtained using standard NR method. Furthermore, the saturated values of magnetizing inductances were obtained and compared using the new and standard NR methods. It was observed that no numerical errors were introduced as a result of using the new technique. The numerical values accurately matched not only in the whole part of the value, but also in the fraction part to the third and fourth digit. It was further observed that the higher the degree of magnetic saturation in the example considered, the faster the new technique in convergence to accurate values

A 3-D Finite Element Perturbational Method for Determining Saturated Values of Transformer Winding Including Experimental Verification

A method is presented in this paper for the calculation of saturated transformer winding inductances. The method is mainly based on an energy perturbation technique in conjunction with non linear three dimensional finite element vector potential field solutions. The concepts of apparent, effective and incremental inductances were utilized in the methodology presented. The method presented was successfully applied in the calculation of apparent, effective and incremental inductance values of the primary winding of a single phase transformer. Very good agreement between calculated and measured values of inductance was accomplished. The work presented provides methodologies by which one would be able to determine, in conjunction with nonlinear three dimensional field solutions, these values of inductances. These inductance values are very important in the dynamic analysis of electrical devices, steady state calculation as well as energy storage and other related analysis and preformance studies

Special Losses in Rotors of Electronically Commutated Brushless DC Motors Induced by Non-Uniformly Rotating Amature MMFS

This paper analyzes special eddy current losses induced in the rotor of an electronically commutated permanent magnet motor powered from a d.c. source, on account of the non-uniform rotation of the stator field. Formulas are established for the losses induced by the tangential component of the stator magnetic field. These formulas are applied to a specific motor design where the magnet retainment was accomplished by means of a metallic nonmagnetic stainless steel sleeve surrounding the rotor structure. The resulting losses are given with consequent conclusions

Nonlinear Vector Potential Formulation and Experimental Verification of Newton-Raphson Solution of Three Dimensional Magnetostatic Fields in Electrical Devices

An iterative technique, based on magnetic vector potential formulation and the Newton-Raphson method, for the determination of the three dimensional magnetostatic field distributions in electrical devices is given. The proper degrees of magnetic saturation in the various materials within a given volume under consideration are obtained by repeated evaluation of the reluctivities in that volume, using a cubic spline representation of the B-H magnetization characteristics of composite materials (laminations). The formulation has been applied to a practical example of determining the field in and around a shell type 1.5 kva single phase transformer. The convergence and implementation characteristics of the developed method are given in this paper which show a saving of about 34% in CPU solution time in comparison with previously published methods. Experimental verification is given in terms of a comparison between computed and experimentally obtained values of flux densities surrounding the transformer core and winding, under heavily saturated conditions. Excellent agreement between test and calculated flux densities was achieved. This method is thus quite applicable to the solution of a wide class of three dimensional magnetostatic field problems associated with electrical apparatus

Validity of Finite Element Formulation and Solution of Three Dimensional Magnetostatic Problems in Electrical Devices with Applications to Transformers and Reactors

This paper shows that the three dimensional magnetostatic field formulation based on the magnetic vector potential curl curl equationi yields unique field solutions in the practical inhomogeneous, anisotropic case with a positive definite reluctivity tensor (laminated cores, etc.). It is also shown that this can be accomplished without the imposition of other constraints on the divergence of the vector potential, and still one obtains unique magnetic vector potential solutions. It will also be shown that in the finite element formulation, the stationary point of the energy functional is the minimum energy point

Nonlinear Three Dimensional Field Computation Methods in Laminated Iron Cores under Saturated Conditions

Two methods of accounting for magnetic saturation in nonlinear three dimensional magnetic field problems using finite elements, are given. The magnetic field formulation used here is based on the curl curl approach which was detailed in earlier papers. The three dimensional finite element method is used once in conjunction with the Newton Raphson technique and once with a Gaussian method to obtain solutions of such fields in the presence of magnetic saturation in laminated cores. The laminated iron core of an example transformer is represented by three composite reluctivities to account for the anisotropy of the core. The saturated values of these composite reluctivities are obtained by curve fitting the magnetization characteristics of composite materials using cubic spline polynomials in conjunction with special treatment of the highly saturated core regions. For comparison purposes, solutions obtained using the Newton-Raphson and the Gaussian methods of inclusion of saturation, are obtained for the same problems in the presence of same degrees of saturation. Very good agreement between calculated and measured data for the chosen problem is achieved. Comparison between convergence and implementation characteristics of the two methods used here are given