Coupled Electromagnetic-Structural Analysis of the Spiraling Phenomenon in a Helical Winding of a Power Transformer

• Published in: IEEE transactions on power delivery Vol. 29; no. 1; pp. 235 - 240
• Main Authors: Bakshi, Amit, Kulkarni, S. V.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-02-2014; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Conductors; Electrical engineering. Electrical power engineering; Electromagnetic forces; Exact sciences and technology; Finite element analysis; Finite-element method; Force; Helical winding; Leakage; Magnetomechanical effects; Magnetostatics; Mathematical analysis; Mathematical models; Power electronics, power supplies; Safety; spiraling; Stress; torsional forces; Transformers; Transformers and inductors; Windings; Structural design; Magnetic flux; Finite-element method; Leakage flux; helical winding; spiraling; Low voltage; Elastoplasticity; Safety; Magnetic field; Machine windings; transformers; Short circuit currents; Electromagnetism; Magnetostatics; Mechanical component; Electromagnetic force; Power electronics; Power transformer; Failures; Short circuit; Field distribution; Flux density; Mechanical stress; torsional forces; Numerical simulation; Structural analysis
• ISSN: 0885-8977; 1937-4208
• DOI: 10.1109/TPWRD.2013.2276047

Spiraling of conductors in a helical winding of a transformer may lead to a catastrophic failure under the action of torsional short-circuit electromagnetic forces. Torsional forces are produced by the interaction of the axial component of the short-circuit current and the radial component of the leakage magnetic flux density. In this paper, 3-D magnetostatic analysis has been performed to determine the leakage magnetic-field distribution in a 130-MVA power transformer. Torsional electromagnetic forces are calculated from the analysis to determine circumferential displacements of conductors of its low-voltage helical winding. Furthermore, mechanical stress components are computed and a factor of safety is defined, which gives an indication as to whether the winding conductors are in the elastic or plastic zone. The numerical results thus obtained by the finite-element method are verified using the first principles from mechanics. The effect of looseness in the inner support structure on the von-Mises equivalent stress and, hence, on the factor of safety has been studied.