OBLONG CORE CROSS-SECTION IMPACT ON POWER TRANSFORMER CHARACTERISTICS
Keywords:Power Transformer Design, Magnetic Core, Oblong (Oval) Cross-Section, Commission Regulation (EU) No 548/2014, Ecodesign Regulations, Directive 2009/125/EC
On the 1st of July 2021, the second phase of 548/2014 EU Regulation, which implements the 2009/125/EC Directive and imposes the maximum level of losses for transformers, entered into force. Some manufacturers have responded to the challenge of reducing the losses by manufacturing power transformers with an elongated core cross-section. In this context, the paper proposes an algorithm to generalize the steps (stacks of laminations) sizing procedure for the core cross-section of power transformers, an algorithm that allows the transition from a circular to an oblong core cross-section. Thus, the dimensions of the laminations stacks which is making up the core cross-section could be estimated for any predetermined value of cross-section diameter. An example of using the proposed algorithm and the impact analysis of the oblong cross-section is applied for an oil cooling power three-phase transformer with a 250kVA rated power. For the oblong cross-section design solution, decreases of the transformer core dimensions and the no-load losses were obtained.
(1) M. Cuesto, M. Oliva, K. Pollari, Driving down energy losses in transformers, Transformers Magazine, 6, 4, pp.67-71 (2019).
(2) ***Commission Regulation (EU) No 548/2014 (EcoDesign Regulations). Online at: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex%3A32014R0548 (accessed in 11.06.2021, 14.02.2022).
(3) L. Dumitru, V. Manescu (Paltanea), G. Paltanea, H. Gavrila, Magnetocrystalline anisotropy in thin grain oriented silicon iron alloy cut through different technologies, Rev. Roum. Sci. Techn. – Électrotechn. Et Énerg., 61, 3, pp. 221–226 (2016).
(4) L. Petrescu, V. Ioniță, E. Cazacu, M.C. Petrescu, Power losses estimation for FeSi sheets using algebraic models, Rev. Roum. Sci. Techn. – Électrotechn. Et Énerg., 64, 1, pp. 23–26 (2019).
(5) ***Teck Global Website, The Differences Between Square, Oblong and Circular Transformer Cores, 2017, Online at: https://teckglobal.com.au/news/41-differences-square-oblong-circular-transformer-core. (accessed in 10.03.2021).
(6) ***Zenithar Foreign Trade & Consulting Website, How Transformer Core Design and Production will be Effected from Eco Design Directive Losses?, 2021, Online at: https://www.zenithar.net/how-transformer-core-design-and-production-will-be-effected-from-eco-design-directive-losses/. (accessed in 11.06.2021, 15.02.2022).
(7) ***GBE Website. Resin: also with oval section. 2021, Online at: https://www.gbeonline.com/en/resin-aslo-with-oval-section/. (accessed in 11.06.2021).
(8) ***SGB-SMIT Group Website, Oval Core and Coil Geometry for Oil Cooled Distribution Transformers, 2016, Online at: https://www.sgb-smit.com/epower/latest-issue/epower-issue-032012/epower-detailansicht/article/oval-core-and-coil-geometry-for-oil-cooled-distribution-transformers/. (accessed in 15.02.2022).
(9) A. Bertuzzi, Innovative solutions for distribution transformer cores and windings, Transformers Magazine, 6, 2, pp.92-101 (2019).
(10) P. Shuai, J. Biela, Influence of material properties and geometric shape of magnetic cores on acoustic noise emission of medium-frequency transformers, IEEE Transactions on Power Electronics, 32, 10, pp. 7916-7931 (2017).
(11) N. Meško, B. Ćućić, D. Žarko, Short-circuit stress calculation in oval windings, Procedia Engineering, 202, pp. 319-326 (2017).
(12). N. Meško, B. Ćućić, D. Žarko, “Critical stress of oval foil winding with epoxy coated insulation determined using measured equivalent modulus of elasticity”, Automatika, 61, 3, pp. 388-395 (2020).
(13) T. Tudorache, O. Caiu, Electrical machines. Laboratory works and problems. Editura Politehnica Press, p. 14-26 and p. 46-48, 2013.
(14) R.M. Del Vecchio et al., Transformer design principles: with applications to core-form power transformers. Second Edition, CRC Press Taylor and Francis Group, p. 9-10, 2010.
(15) M. Morega, Optimizare tehnico-economică (Technical and Economic Optimization), course notes 2018-2019 Faculty of Electrical Engineering, University Politehnica of Bucharest, (in Romanian).
(16) I. Cioc, C. Nica, Proiectarea mașinilor electrice (Design of Electrical Machines), Editura Didactică și Pedagogică, București, p. 771-905, 1994 (in Romanian).
(17) N. Bichir, V. Stanciu, Proiectarea şi reproiectarea transformatoarelor electrice (Design and Redesign of Electrical Transformers), Editura ICPE, Bucureşti, 2001 (in Romanian).
(18) ***Maple User Manual, Copyright © Maplesoft, a division of Waterloo Maple Inc. 2014.