Influence of transformer core design on power losses

Valković, Zvonimir

doi:10.1109/tmag.1982.1061824

Cited by 31 publications

(8 citation statements)

References 5 publications

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“…It should be noted that drastic discrepancies were found among different results as it was reported in [8] and [ll]. The existence of an optimum of the overlap length has been one of the major disagreements.…”

Section: A Experimental Studiesmentioning

confidence: 89%

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Anisotropy in three-phase transformer circuit model

Elleuch

Poloujadoff²

1997

IEEE Trans. Magn.

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Abstruct-In this paper, an important discussion of transformer design and modeling is given. Afterwards, the anisotropy effects of the transformer laminations have been stressed in light of the investigation of a three-phase three-limb transformer Tjoint. Three simple T-joint modeling schemes accounting for the lamination anisotropy are proposed. The fundamental result is that the flux lines remain almost parallel to the rolling direction (RD), except in a small area around the T-joint. Therefore, transformer yokes and limbs have been divided into longitudinal elements according to the RD. Reluctances related to these elements are connected according to the magnetic circuit coupling and yield a new transformer circuit model. A good agreement is obtained between computed and measured transients currents. Furthermore, the new transformer model enables some localized analysis. The computed localized fluxes and loci of flux density vectors near to the T-joint exhibit a satisfactory agreement with many results based on FEM or experimental investigations.Zndex Terms-Grain-oriented steels, transformer.

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Section: A Experimental Studiesmentioning

confidence: 89%

“…Interesting conclusions and suggestions were mentioned in many papers with regard to the joint models [4], [6]- [9], optimum overlap [8]-[ 121, number of laminations per stagger layer [8], [ll], and the core shape (aspect ratio) [5], [8], [lo].…”

Section: A Experimental Studiesmentioning

confidence: 99%

Anisotropy in three-phase transformer circuit model

Elleuch

Poloujadoff²

1997

IEEE Trans. Magn.

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“…Reference [27] reported complete data of a constructed core and measured core loss. This core is made of CRGO (grade M5) and by mitred 45˚ joints.…”

Section: Verification With Constructed Coresmentioning

confidence: 99%

Power Transformer No-Load Loss Prediction with FEM Modeling and Building Factor Optimization

Hajipour¹,

Rezaei²,

Vakilian³

et al. 2011

JEMAA

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Estimation of power transformer no-load loss is a critical issue in the design of distribution transformers. Any deviation in estimation of the core losses during the design stage can lead to a financial penalty for the transformer manufacturer. In this paper an effective and novel method is proposed to determine all components of the iron core losses applying a combination of the empirical and numerical techniques. In this method at the first stage all computable components of the core losses are calculated, using Finite Element Method (FEM) modeling and analysis of the transformer iron core. This method takes into account magnetic sheets anisotropy, joint losses and stacking holes. Next, a Quadratic Programming (QP) optimization technique is employed to estimate the incomputable components of the core losses. This method provides a chance for improvement of the core loss estimation over the time when more measured data become available. The optimization process handles the singular deviations caused by different manufacturing machineries and labor during the transformer manufacturing and overhaul process. Therefore, application of this method enables different companies to obtain different results for the same designs and materials employed, using their historical data. Effectiveness of this method is verified by inspection of 54 full size distribution transformer measurement data

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“…• the physical origin of those losses, characterizing the intrinsic quality, as evaluated by standard measurements such as the Epstein apparatus [25]; • the deterioration of the intrinsic qualities by sheet punching and various handling [26], [34]; • the geometry and design of the magnetic circuit (size, sheet arrangement, joint models, number of sheets in each stack [25] ). It is customary to define a "building factor" as the ratio [32], [33], [65]- [67] total iron losses in magnetic circuit iron losses predicted by Epstein apparatus Prediction of (of the total losses) is a difficult task.…”

Section: Correlation With the Building Factormentioning

confidence: 99%

“…c) A global model accounts for the fact that the sheets exhibit higher losses within a transformer than in an Epstein apparatus. This excess (15% to 20% [24], [25]) results from local saturation in the vicinity of joints, from rotating fields in the vicinity of T joints, and of the local distortion of flux density [2], [3], [26]- [33], as well as the deterioration of sheets during manufacturing [34]. As a result, an accurate theoretical approach of iron losses seems difficult.…”

Section: Introductionmentioning

confidence: 99%

Analytical model of iron losses in power transformers

Elleuch¹,

Poloujadoff²

2003

IEEE Trans. Magn.

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We have improved a circuit model of transformers by defining a conductance whose losses will be close to the iron losses under any circumstance. Connecting a constant conductance cs in parallel with the main magnetizing inductance is very popular in the literature; however, it is acceptable only if the flux amplitude and frequency are reasonably constant during the time of operation, and if the value can be properly adjusted. Here, we replace cs with a nonlinear dynamic conductance cd , whose losses are a function of flux amplitude. This conductance is based on the concept of dynamical hysteresis. Its definition is such that it is determined by the same test results used for cs . Knowing the values of losses given by the manufacturer of the sheets, and the measured values of iron losses of a transformer, we can then analytically express the building factor as a function of the maximum flux density. We have applied the method to a three-leg 10-kVA transformer. It allows us to identify the cases when iron losses may be ignored, when they may be represented by a constant conductance, and when they must be represented by a nonlinear conductance.

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Influence of transformer core design on power losses

Cited by 31 publications

References 5 publications

Anisotropy in three-phase transformer circuit model

Anisotropy in three-phase transformer circuit model

Power Transformer No-Load Loss Prediction with FEM Modeling and Building Factor Optimization

Analytical model of iron losses in power transformers

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