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Abstract

The Goss texture is a characteristic feature of grain-oriented transformer steel sheets. Generator sheets, which are produced as non-oriented steel sheets, should have isotropic features. However, measurement results of generator sheets, confirmed by crystallographic studies, indicate that these sheets are characterized by certain, quite significant anisotropy. The first purpose of this paper is to present the influence of textures of generator and transformer steel sheets on their magnetization characteristics. The second aim is to propose a method which takes into account the sheet textures in the calculations of magnetization curves. In calculations of magnetization processes in electrical steel sheets, models in which the plane of a sheet sample is divided into an assumed number of specified directions are used. To each direction a certain hysteresis loop, the so-called direction hysteresis, is assigned. The parameters of these direction hystereses depend, among other things, on the texture type in these steel sheets. This paper discusses the method which calculates the parameters of these direction hystereses taking into account the given sheet texture. The proposed method gives a possibility of determining the magnetization characteristics for any direction of the field intensity changes.
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Abstract

Energy based approach was used in the study to formulate a set of functions approximating the magnetic flux linkages versus independent currents. The simplest power series that approximates field co-energy and linked fluxes for a two winding core of an induction machine are described by a set of common unknown coefficients. The authors tested three algorithms for the coefficient estimation using Weighted Least-Squared Method for two different positions of the coils. The comparison of the approximation accuracy was accomplished in the specified area of the currents. All proposed algorithms of the coefficient estimation have been found to be effective. The algorithm based solely on the magnetic field co-energy values is significantly simpler than the method based on the magnetic flux linkages estimation concept. The algorithm based on the field co-energy and linked fluxes seems to be the most suitable for determining simultaneously the coefficients of power series approximating linked fluxes and field co-energy.
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Abstract

Magnetic measurements, carried out by means of the Epstein frame, have shown that most typical dynamo steel sheets have certain anisotropic properties. In numerical analysis, anisotropic properties are taken into account with the use of the special function of the grain distribution in the given dynamo sheet. For engineering purposes, it is desirable to assess the influence of these properties on the changes of the magnetic flux density in typical dynamo steel sheets, especially during the rotational magnetization. For this purpose, measurements of the flux density changes and field strength changes in the circular-shaped samples of two selected typical dynamo sheets were performed. These measurements were carried out for several values of the current flowing in windings which generated the axial or rotational magnetic field in the test dynamo sheet. The influence of the magnetic anisotropy on the magnetization process was briefly discussed for both types of the magnetization processes.
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