Lamination of T-joints in the transformer core

Pietruszka, Maria; Napieralska‐Juszczak, Ewa

doi:10.1109/20.497454

Cited by 11 publications

(4 citation statements)

References 7 publications

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“…7 should not be interpreted as a comparison between experiment and computation; instead the curves are merely superimposed to demonstrate that the characteristics of the different structures lie between the two extremes as given by the two directions of rolling. This result was to be expected as the actual structures are built from laminations of various combinations of anisotropy angles [2], [18]. The computed equivalent characteristics are then used to represent the 3-D effects using 2-D simulations.…”

Section: A Numerical Resultsmentioning

confidence: 99%

“…The flux density of the equivalent structure of the air gap may then be defined as (1) where is the equivalent flux density of the structure, the density in the yoke sheet, the density in the column sheet, and finally the flux density in the air gap. The energy stored in the virtual gap in the joint is (2) where and are the reluctivities of the yoke and the limb, respectively, while and is the lamination volume. In (2), the energy has been approximated using a linearized model which is a common approach in electromagnetic software packages.…”

Section: B Description Of the Methodsmentioning

confidence: 99%

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Equivalent Permeability of Step-Lap Joints of Transformer Cores: Computational and Experimental Considerations

et al. 2011

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The paper develops an efficient computational method for establishing equivalent characteristics of magnetic joints of transformer cores, with special emphasis on step-lap design. By introducing an equivalent material, the method allows the real three-dimensional structure of the laminated thin sheets to be treated computationally as a two-dimensional problem and enables comparative analysis of designs. The characteristics of the equivalent material are established by minimizing the magnetic energy of the system. To verify the proposed approach, a series of experiments have been conducted. First, the anisotropic characteristics of the step-lap were established, and then space components of the flux density at specified positions measured. This enabled detailed analysis of the flux distribution in the step-lap region, in particular the way in which the flux travels between the laminations close to the air-gap steps. Encouraging correlation between the homogenized 2-D model and experiment has been observed.

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Section: A Numerical Resultsmentioning

confidence: 99%

Section: B Description Of the Methodsmentioning

confidence: 99%

Equivalent Permeability of Step-Lap Joints of Transformer Cores: Computational and Experimental Considerations

et al. 2011

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“…The use of the homogenization technique in the finite element method (FEM) analysis of step-lap joints in steel sheet transformers was proposed in [45]. The homogenization technique was further developed in 2D FEM of steel sheet cores [46][47][48] and amorphous cores [49]. The multiscale methods were proposed in the analysis of the magnetic properties of transformer cores in [50].…”

Section: Mft Vsc1 Vsc2mentioning

confidence: 99%

Effective Permeability of Multi Air Gap Ferrite Core 3-Phase Medium Frequency Transformer in Isolated DC-DC Converters

et al. 2020

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The magnetizing inductance of the medium frequency transformer (MFT) impacts the performance of the isolated dc-dc power converters. The ferrite material is considered for high power transformers but it requires an assembly of type “I” cores resulting in a multi air gap structure of the magnetic core. The authors claim that the multiple air gaps are randomly distributed and that the average air gap length is unpredictable at the industrial design stage. As a consequence, the required effective magnetic permeability and the magnetizing inductance are difficult to achieve within reasonable error margins. This article presents the measurements of the equivalent B(H) and the equivalent magnetic permeability of two three-phase MFT prototypes. The measured equivalent B(H) is used in an FEM simulation and compared against a no load test of a 100 kW isolated dc-dc converter showing a good fit within a 10% error. Further analysis leads to the demonstration that the equivalent magnetic permeability and the average air gap length are nonlinear functions of the number of air gaps. The proposed exponential scaling function enables rapid estimation of the magnetizing inductance based on the ferrite material datasheet only.

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“…The accurate electromagnetic simulation of devices containing laminated conductive cores, including eddy current effects, often turns out because of high computational time due to the full discretization of each sheet of a laminated core and the space between them. The authors have proposed earlier (Pietruszka et al, 1996;Hihat et al, 2008) method to determine equivalent homogenized magnetic characteristics of structures built with anisotropic laminations. However, the first model neglects the effects of hysteresis and eddy currents.…”

Section: Introductionmentioning

confidence: 99%

Simplified models including eddy currents for laminated structures

Hihat

Komęza

Napieralska‐Juszczak

et al. 2010

COMPEL - The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

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Purpose -The purpose of this paper is to present a comparative analysis concerning the influence of eddy currents on the distribution of the magnetic flux density in the laminated anisotropic structures. Design/methodology/approach -The influence of the magnetic flux normal to the lamination surface is particularly analysed. Several models containing internal air gaps and overlapping are tested. For every structure, the eddy currents are first taken into account and then, they are neglected. At last, the 3D simulation of the anisotropic conductivity permits to analyse separately the longitudinal and normal flux in the structure and the eddy currents induced by those fluxes. Findings -The study leads to a more realistic numerical model with conducting laminations. The results show that the normal flux does not turn at once on lamination. The normal and longitudinal fluxes induce eddy currents which modify the flux distribution in the laminated structure. Practical implications -The results of the presented simulations make it possible to elaborate a more realistic numerical model of homogenized characteristics taking into account eddy currents. Originality/value -The eddy currents induced by the fluxes modifies the field distribution in the structure and should be taken into account. The internal air-gaps higher than 0.1 mm have an influence on the field distribution; the isolation between the laminations of 0.01 mm has a smaller but not negligible effect on the magnetic flux. The direction of the normal flux from one sheet to another one does not change immediately after the entrance of the lamination, the transition is progressive.

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Lamination of T-joints in the transformer core

Cited by 11 publications

References 7 publications

Equivalent Permeability of Step-Lap Joints of Transformer Cores: Computational and Experimental Considerations

Equivalent Permeability of Step-Lap Joints of Transformer Cores: Computational and Experimental Considerations

Effective Permeability of Multi Air Gap Ferrite Core 3-Phase Medium Frequency Transformer in Isolated DC-DC Converters

Simplified models including eddy currents for laminated structures

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