With the fast-paced changing technologies in the power industry, new references addressing new technologies are coming to the market. Based on this fact, there is an urgent need to keep track of international experiences and activities taking place in the field of modern transformer design. The complexity of transformer design demands reliable and rigorous solution methods. A survey of current research reveals the continued interest in application of advanced techniques for transformer design optimization. This paper conducts a literature survey and reveals general backgrounds of research and developments in the field of transformer design and optimization for the past 35 years, based on more than 420 published articles, 50 transformer books, and 65 standards.

Transformer Design and Optimization: A Literature Survey

http://users.ntua.gr/pgeorgil/Files/J16.pdf

A heuristic solution to the transformer manufacturing cost optimization problem

This paper presents results of a rigorous analytical study performed in order to understand the role which joints play in determining the performance of cores of power and distribution transformers. The paper presents the details of the magnetic flux distribution and redistribution in the core joint region along the core stack height direction as a function of the operating flux density, core joint material, joint configuration, and joint design parameters. The results are presented for both conventional and step-lap joints. The results illustrate the benefits of the step-lap joint in reducing core losses, noise and excitation current. The results also explain the impact of overlap length, the number of laminations per step, and the contribution of the joint region to the whole core performance. The calculated flux density wave shapes in the joint region were found to be in good agreement with measured wave shapes. The results presented in this paper have been used in developing an accurate calculation of core losses for both power and distribution transformers. They have also been used to arrive at the optimum core joint configuration for a transformer core.

Magnetic flux distributions in transformer core joints

The paper presents an effective method to reduce the iron losses of wound core distribution transformers based on a combined neural network/genetic algorithm approach. The originality of the work presented is that it tackles the iron loss reduction problem during the transformer production phase, while previous works concentrated on the design phase. More specifically, neural networks effectively use measurements taken at the first stages of core construction in order to predict the iron losses of the assembled transformers, while genetic algorithms are used to improve the grouping process of the individual cores by reducing iron losses of assembled transformers. The proposed method has been tested on a transformer manufacturing industry. The results demonstrate the feasibility and practicality of this approach. Significant reduction of transformer iron losses is observed in comparison to the current practice leading to important economic savings for the transformer manufacturer.

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A novel iron loss reduction technique for distribution transformers based on a combined genetic algorithm - neural network approach

Methods for iron loss reduction during manufacturing of wound-core distribution transformers are presented. More specifically, measurements taken at the first stages of core construction are effectively used, in order to minimize iron losses of transformer (final product). To optimally exploit the measurements (feedback), artificial intelligence methods are applied. It is shown that intelligent systems are able to learn and interpret several variations of the same conditions, thus helping in predicting iron losses with increased accuracy.

AI helps reduce transformer iron losses

This paper describes an analytical solution to use a generic 2D finite difference method to accurately calculate the quasi 3D spatial distribution, components, and total core losses in transformer cores. The solution takes into account: (1) magnetic anisotropy and nonlinearity of the core material; (2) all components of iron losses of the core material, including losses in directions other than the rolling direction; and (3) joint model and localized losses due to the distorted flux distribution in the joint regions (due to core gaps) across the core-stack. The results are used to: (1) calculate very accurately the total core losses of a transformer at the design stage every time, for all core materials, at all operating inductions, for all core geometries, for both 50 Hz and 60 Hz; (2) understand the contribution of cross losses, harmonics, and joints to the total losses of a core; (3) evaluate the impact of various joint attributes, such as, type of joint, number of steps, number of laminations per step, size of gaps, and lamination thickness on the total performance of the core; and (4) improve the core loss performance of transformers by optimizing core design and core material parameters. This paper presents the analysis as applied to 3-phase, 3-limb cores. The paper also presents the results of the extensive experimental/test verification performed on a number of model cores in the lab as well as on a large number of actual commercial transformer cores with excellent agreements. The results have been used to calculate core losses of stacked power and distribution transformers with consistent accuracy.

R.S. Girgis

Papers

Calculation of spatial loss distribution in stacked power and distribution transformer cores