Analysis of electromagnetic and loss effects of sub-harmonics on transformers by Finite Element Method
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Sådhanå (2020) 45:226 https://doi.org/10.1007/s12046-020-01473-4
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Analysis of electromagnetic and loss effects of sub-harmonics on transformers by Finite Element Method ¨ ZU ¨ PAK1,* YILDIRIM O
and MEHMET SALIH MAMIS¸ 2
1
Silvan Vocational School, Dicle University, Diyarbakır, Turkey Department of Electrical and Electronic Engineering, I˙no¨nu¨ University, Malatya, Turkey e-mail: [email protected]; [email protected]
2
MS received 1 May 2020; accepted 5 July 2020 Abstract. Power transformers are generally designed to be used in conditions where voltage and current are sinusoidal. However, nonlinear loads are increasing in modern power systems with the developing technology. Therefore, line voltages and currents often have harmonically distorted or non-sinusoidal waveforms. In this article, a model has been developed. The mathematically developed model has been proven experimentally and numerically. In this paper, different sub-harmonic content parametric analysis of the loss of transformer under no-load conditions with voltage excitation was performed. For this purpose, the Finite Element Method (FEM) based modeling of the core and windings of the transformer has been developed. An efficient method based on harmonic field model of transformer windings and FEM based modeling of transformer core is used. ANSYS@MAXWELL program, which realizes a solution based on FEM, is used for this. From the results of the analysis, it was seen that the effect of harmonic voltages on the loss of the transformer core is negligible. However, these tensions have been shown to increase winding losses in the unloaded state. This case reveals the importance of harmonics to be taken into account in calculating the losses of power transformers. Keywords.
Harmonic; finite element method; transformer losses; electromagnetic flux.
1. Introduction Transformers are one of the most important equipment for the transmission and distribution of electrical energy in AC power networks. In electrical engineering literature, measurement and calculation of core and winding losses are well known for sinusoidal voltage and linear load (sinusoidal current) conditions. The no-load loss of a transformer is the sum of the active powers consumed by its core and powered winding when it does not provide a load. The no-load loss is practically considered to be the core loss, since the winding loss under the sinusoidal excitation voltage at nominal frequency in the no-load condition is quite small. In addition, the winding loss is often referred to as load loss, since the winding loss of a power transformer is significantly larger than the base loss for the rated loading condition. In modern power systems, the large increase of nonlinear loads caused harmonic distortions. This situation has made the effect of harmonics on power transformers. Non-sinusoidal currents cause excessive winding losses, transformers overheating, and reduced useful life. An efficient technique called derating is wid
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