Mechanical Force Analysis in Heavy-Current HTS Transformers Based on Field and Current Nonuniformity Coupled Analysis

Mechanical stresses of magnetically induced origins are becoming more serious with the trend of high-temperature superconductor (HTS) heavy-current transformer (HCT) applications. Mechanical forces in HTS HCTs that act on the transformer windings are generated by the interaction between the current density and the leakage flux density. This paper presents the calculation of leakage flux and mechanical force distribution in high-current HTS transformer windings. This requires the need for advanced numerical techniques for simulation studies using finite-element method by adapting two auxiliary windings for the leakage flux mitigation and, thereby, mechanical forces within the main windings. A model is developed for the calculation of mechanical force considering nonuniformity of both field and current distributions in the windings, which is the main motivation for initiating this paper.

[2]  H. Heydari,et al.  Mechanical forces simulation of 25 kA current injection transformer with finite element method , 2005, 2005 International Power Engineering Conference.

[3]  H. Heydari,et al.  The effects of windings current density values on leakage reactance in a 25 kA current injection transformer , 2005, 2005 International Power Engineering Conference.

[4]  Thomas Baldwin,et al.  Design optimization of high-temperature superconducting power transformers , 2003 .

[5]  W. J. McNutt,et al.  Power Transformen Short-Circuit Strength - Requirements, Design, and Demonstration , 1970 .

[6]  Kyung-Woo Ryu,et al.  Magnetization loss characteristics in a stack of Bi-2223 tapes , 2003 .

[7]  H. Heydari,et al.  Simulation and analysis of 25 kA current injection transformer (CIT) with finite element method , 2004, Proceedings of the 12th IEEE Mediterranean Electrotechnical Conference (IEEE Cat. No.04CH37521).

[8]  J Kokavec,et al.  Mechanical stresses in cylindrical superconducting coils , 1977 .

[9]  Faramarz Faghihi,et al.  A new approach for AC loss reduction in HTS transformer using auxiliary windings, case study: 25 kA HTS current injection transformer , 2007 .

[10]  S. Mukoyama,et al.  Uniform current distribution conductor of HTS power cable with variable tape-winding pitches , 1999, IEEE Transactions on Applied Superconductivity.

[11]  S. M. Pedramrazi.  Impact of Mechanical Forces in a 25kA Current Injection Transformer , 2007 .

[12]  A. Allais,et al.  Mechanical Requirements for Superconducting Tapes in HTS Power Cable Applications , 2007, IEEE Transactions on Applied Superconductivity.

[13]  Gueesoo Cha,et al.  Test of a high T/sub c/ superconducting power transformer , 2000, IEEE Transactions on Applied Superconductivity.

[14]  K. Feser,et al.  Procedures for detecting winding displacements in power transformers by the transfer function method , 2004, IEEE Transactions on Power Delivery.