Bio: G. Swift is an academic researcher from University of Manitoba. The author has contributed to research in topics: Distribution transformer & Current transformer. The author has an hindex of 1, co-authored 1 publications receiving 18 citations.
TL;DR: In this paper, the impact of the 45° mitered-overlap joint on the performance of large power transformer cores with respect to core loss and exciting current was investigated.
Abstract: The 45° mitered-overlap joint is commonly used in the construction of large power transformer cores. There are several variables which affect the performance of such cores with respect to core loss and exciting current. The major variables investigated in this paper are 1) overlap distance, 2) stagger layer thickness, and 3) overlap method, namely, simple staggering versus step-lap. Also investigated to a lesser degree were the effect of frequency and the effect of series air gaps at the corners. One set of results in this paper is not in agreement with a previous paper and reasons for this are speculated. The other sets of results are new, and indicate that staggering beyond two laminations per stagger is not advisable, that the difference between one and two laminations per stagger is marginal, and that the use of a step-lap joint reduces exciting current requirements but not core loss.
TL;DR: In this article, the authors conduct a literature survey and reveal 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.
Abstract: 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.
TL;DR: In this paper, the influence of the V-45° T-joint on the magnetic properties of a three-phase core has been investigated, and the effect of the corner joint overlap length, the number of laminations per stagger layer and the yoke cross-section form on the core building factor has been determined.
Abstract: The results of an experimental investigation on reduced models of the influence of core design on core losses are presented. The characteristics of single-phase and three-phase three-limbed cores are compared, and the influence of the core proportions on the core building factor is determined. Four types of T-joint design for a three-phase core have been investigated. It has been found that the widely applied V-45° T-joint does not have the best magnetic properties, as usually assumed. The influence of the corner joint overlap length, the number of laminations per stagger layer, and the yoke cross-section form on the core building factor have been determined.
TL;DR: In this paper, three simple T-joint modeling schemes accounting for the lamination anisotropy are proposed, and a good agreement is obtained between computed and measured transient currents.
Abstract: In this paper, an important discussion of transformer design and modeling is given. Anisotropy effects of the transformer laminations have been stressed in the light of the investigation of a three-phase three-limb transformer T-joint. 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 transient 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.
TL;DR: 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 to improve the core loss estimation over the time when more measured data become available.
Abstract: 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.
TL;DR: In this article, a finite element method is developed to compute alternating electromagnetic fields in laminated cores and power losses in mitered overlap joints are evaluated for cores with different overlap lengths.
Abstract: A finite element method is developed to compute alternating electromagnetic fields in laminated cores. The method is applied to a simplified model problem in order to evaluate power losses in mitered overlap joints. The influence of eddy currents on the magnetic field distribution in the neighborhood of the mitered joints is discussed. The power losses ate evaluated for cores with different overlap lengths.