R. Sugawara

Bio: R. Sugawara is an academic researcher. The author has contributed to research in topics: Distribution transformer & Linear variable differential transformer. The author has an hindex of 1, co-authored 1 publications receiving 9 citations.

Characteristics of a 40 kVA three phase superconducting transformer and its parallel operation with a conventional transformer

Abstract: A 40 kVA three phase superconducting transformer has been developed and tested. From the test results, excellent voltage regulation of 0.3% with a pure resistive load was obtained. For application in a power system, parallel operation with a conventional power transformer using copper windings has been carried out. Although a superconducting transformer cannot continue to operate in case of quenching, the proposed parallel system can overcome the drawback and give an additional fault current limiting function. >

NbTi wires with ultra-fine filaments for 50-60 Hz use: influence of the filament diameter upon losses

Abstract: Filaments de NbTi dans une matrice de CuNi. On obtient une bonne stabilite magnetique, les pertes a 50 Hz sont fortement reduites. Possibilites d'application de la supraconductivite dans des aimants en impulsions rapides et dans des dispositifs a courant alternatif. Resultats de mesures de pertes a 50 Hz; influence du diametre des filaments

Prospects for large high-temperature superconducting power transformers: conclusions from a design study

Abstract: A design feasibility study has been conducted for a 240 MVA high-temperature superconducting grid auto-transformer. Conclusions are relevant to superconducting power transformers in general. It is argued that economic benefits may be predicted, subject to assumptions about achievable conductor properties, costs of components and power system operating requirements. Liquid nitrogen cryogenics is relatively cheap and simple, and refrigeration power demand is reduced by a factor of the order of 20 compared to the low-temperature case. Attention is drawn to the importance of AC losses in the superconductor and the difficulty of keeping these sufficiently low. Various technical problem areas, and their likely influence on the overall design concept, are reviewed. Three particularly important influences are identified: insulating properties of liquid nitrogen coolant; required transformer performance in the through fault condition; and mechanical strength to withstand electromagnetic forces. Design proposals are detailed, and recommendations made for future development of high-temperature superconductors for power applications.

Core loss and excitation current model for wound core distribution transformers

Abstract: SUMMARY This paper proposes a model for the computation of core losses and excitation current, in a lamination by lamination method, for wound core distribution transformers. The model was developed based on the finite-element method (FEM). The results obtained by applying the proposed model were compared with the FEM results and with the measurements of the no-load test. The no-load losses obtained by the proposed model present a difference of 4% with respect to measured values, while they are almost the same with respect to FEM. The proposed model contributes in the research of new techniques that improve transformer design. Copyright © 2012 John Wiley & Sons, Ltd.

A Bibliographic Analysis of Transformer Literature 1990-2000

Abstract: This paper presents an analysis of the bibliography on transformers covering the period from 1990 to 2000. It contains all the transformer subjects: a) Transformer design, b) Transformer protection, c) Transformer connections, d) Transformer diagnostics, e) Transformer failures, f) Transient analysis of transformers (overvoltages, overcurrents), g) Modeling and analysis of transformer using FEM (thermal modeling, losses modeling, insulation modeling, windings modeling). Several international journals were investigated including the following: Advances in Electrical and Computer Engineering, Canadian Journal of Electrical and Computer Engineering, COMPEL (The International Journal for Computation and Mathematics in Electrical and Electronic Engineering), Electrical Engineering, Electric Power Components and Systems, Electric Power Systems Research, European Transactions on Electrical Power, IEEE Transactions on Magnetics, IEEE Transactions on Power Delivery, International Journal of Electrical Power and Energy Systems, and IET Generation Transmission & Distribution. Due to the high number of publication in journals, we are not considering publications of conferences and symposia. A total of 700 publications are analyzed in this paper. The research presented in this paper is important because it contains and analyzes the best research papers on transformers coming from many countries all over the world and published in top rated scientific electrical engineering journals.

DOE’s program on the application of high-Tc wire

Abstract: The U.S. Department of Energy’s Superconductivity Program for Electric Power Systems is engaged in activities to develop high-critical-temperature superconducting wire technology. The major thrust toward applications is done through the Superconductivity Partnership Initiative, which features four industrial consortia developing precommercial power technology. The success of the program depends on wire performance and cost-meeting application requirements when commercialization activities begin between 1998 and 2000.