Title :
Coupled Electromagnetic-Structural Analysis of the Spiraling Phenomenon in a Helical Winding of a Power Transformer
Author :
Bakshi, Ankita ; Kulkarni, S.V.
Author_Institution :
Dept. of Electr. Eng., Indian Inst. of Technol. Bombay, Mumbai, India
Abstract :
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.
Keywords :
conductors (electric); elasticity; electromagnetic coupling; electromagnetic devices; finite element analysis; magnetic flux; magnetic forces; magnetostatics; plasticity; power transformers; short-circuit currents; stress analysis; transformer windings; 3D magnetostatic analysis; apparent power 130 MVA; circumferential displacement; conductor; coupled electromagnetic-structural analysis; elastic zone; finite-element method; leakage magnetic flux density; leakage magnetic-field distribution; low-voltage helical winding; mechanical stress component; plastic zone; power transformer; short-circuit current; spiraling phenomenon; torsional electromagnetic force calculation; torsional short-circuit electromagnetic force; von-Mises equivalent stress; Conductors; Finite element analysis; Force; Magnetomechanical effects; Magnetostatics; Stress; Windings; Finite-element method; helical winding; spiraling; torsional forces; transformers;
Journal_Title :
Power Delivery, IEEE Transactions on
DOI :
10.1109/TPWRD.2013.2276047