On the continuity of the magnetizing current density in 3-D magnetic field analysis with edge element

The effects of the continuity of the magnetizing current density on the convergence of the incomplete Cholesky conjugate gradient method and the accuracy of the calculated flux densities are investigated by imposing different continuity conditions for both nodal and edge elements. It is shown that the continuity condition should be imposed precisely in the case of edge elements </p

Improvements of single sheet testers for measurement of 2-D magnetic properties up to high flux density

Due to structural limitation, the currently proposed apparatus based on a single sheet tester (SST) cannot measure magnetic properties along arbitrary directions (so-called 2-D magnetic properties) of silicon steel at high flux densities. In this paper, significant improvements are carried out on magnetizing windings and auxiliary yokes of a double excitation type of SST. Furthermore, crosswise overlapped H-coils are introduced so that even an ordinary single-excitation type of SST can be applicable to the measurements of 2-D properties. It is demonstrated that 2-D magnetization property up to 1.9 T can be measured by using the newly developed SST's</p

Practical analysis of 3-D dynamic nonlinear magnetic field using time-periodic finite element method

A practical 3-D finite element method using edge elements for analyzing stationary nonlinear magnetic fields with eddy currents in electric apparatus, in which the flux interlinking the voltage winding is given, has been proposed. The method is applied to the analysis of magnetic fields in the Epstein frame </p

Single sheet tester having open magnetic path for measurement of magnetostriction of electrical steel sheet

A single sheet tester having closed magnetic path (a closed type of SST) has a problem that measurement accuracy of magnetostriction is considerably affected by electromagnetic force between specimen and yoke. Therefore, an open type has been developed. In order to get uniform flux distribution in a sufficiently large region, a compensating magnetizing winding is installed, and a method of waveform control is investigated, in which applied voltages to main and compensating windings are adjusted individually. The effectiveness of the newly developed open type is demonstrated by measuring magnetostrictions of thin amorphous sheet as well as highly grain-oriented silicon steel sheet</p

Factors affecting errors due to 2-D approximate analysis of 3-D magnetic fields with eddy currents [rotating machines]

The effects of the leakage flux, eddy current path, and end coil of electric machines on the flux and eddy current density analyzed by the 2-D approximation are investigated systematically by making a comparison with 3-D analysis. It is shown that, when the gap length is relatively large, the difference between the fluxes calculated by 2-D and 3-D analyses is pronounced due to the leakage flux. The flux in the pole obtained by 3-D analysis is larger than that obtained by 2-D analysis under constant current excitation, and the flux obtained by 3-D analysis is less than that obtained by 2-D analysis under constant voltage excitation. When the eddy current flows in the thin core, a larger error occurs in the 2-D analysis, because there is a great difference in eddy current paths between 2-D and 3-D models</p

A proposal of finite-element analysis considering two-dimensional magnetic properties

A technique for analyzing the magnetic field in anisotropic material using the effective anisotropic reluctivity proposed by Enokizono is examined. It is shown that the Enokizono model can be transformed into another model having a conventional form. By expanding the examination of such a conventional form, a new finite element formulation for taking account of the two-dimensional (2-D) magnetic property is proposed. As the modeling of the 2-D magnetic property at the high flux density region is important in the practical analysis of the magnetic device, the extrapolation method of the magnetic property is examined. It is shown that the Bezier interpolation is fairly effective to stabilize the convergence characteristic of the Newton-Raphson (N-R) iteration in the nonlinear magnetic field analysis, taking account of the 2-D magnetic property </p

Physical meaning of grad&#1060; in eddy current analysisusing magnetic vector potential

The physical meaning of the grad&#966; in the A-&#966; method is investigated in order to determine when it can be safely neglected in order to reduce computation time. The relationship between eddy current distribution and grad&#966; and the effects of boundary conditions on grad&#966; are examined for several 2-D examples. It is shown that grad&#966; in 2-D analysis is a constant that modifies the interlinkage flux of the conductor, which is denoted by the magnetic vector potential A</p

Problems in practical finite element analysis using Preisach hysteresis model

An efficient method, which is called the “inverse distribution function method”, for calculating the magnetic field strength H from the flux density B through the Preisach model is developed. By using the method, H can be directly obtained without iteration from B which is calculated by the usual FEM, with the magnetic vector potential as an unknown variable. The effects of the dimension n of the inverse distribution function on the CPU time and the memory requirements are investigated through a numerical example by increasing the dimension n of the inverse distribution function. It is shown that the additional CPU time for taking account of hysteresis is negligible when n is less than about 200</p