• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.8
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• pp.121-128
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• 2007

In this thesis, we would show how to lay out and produce the shell-type transformer using the world's first Zig-Zag winding way, instead of a general winding. Also, we omit the progress of varnish-impregnation, so that we could develop the new shell-type transformer winding which improves the short-circuit characteristics and dielectric strength. It has a copernican effect to reduce the thickness and the number of insulation papers, as compared with a general winding transformer. We would prove that it is far superior in cost reduction, loss reduction, and mechanical force of short-circuit. And eventually you must find it useful in the pole transformer for power distribution in the domestic power companies.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.6
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• pp.87-95
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• 2006

In this study, in order to obtain high qualify of electric power, single phase active filter which is composed of Zig-Zag transformer and three phase bridge rectifier and capacitor at the secondary of its transformer to be able to reduce the components of the zero phase current and the third harmonic current in neutral line and power line respectively. By connecting this filter to the Zig-Zag transformer and nonlinear load, their third harmonic components due to the nonlinear loads were reduced.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.1
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• pp.169-174
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• 2005

The conventional harmonic filters to reduce zero harmonic current from neutral reactors and Zig-Zag connection, have several disadvantages of the decreased reduction rate of harmonics under a light load, because they have the load factor-dependent reduction rate of harmonics, and the risk of potential breaking in the neutral line by heated neutral reactor. Based Zig-Zag connection and Open-Delta mode, this new harmonic eliminating device (HANOS) adopts the combination of Zig-Zag connection and Open-Delta mode-the latter is additionally applied to the transformer's core block for connection to the neutral line. The results of this study demonstrated that the new device could eliminate safely zero harmonic current running in the neutral line without heating.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.333-338
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• 2014

This paper concerns the development of the transformer that can reduce harmonics supplied to the system if the output of photovoltaic inverter in the photovoltaic system is grid-connected, and suggests that problems of harmonics and power factor degradation in the grid-connected photovoltaic system can be improved. In this study, the burden of increasing the investment in new facilities and securing their installation space due to harmonics has been substantially eased through the development of a hybrid transformer possessing unbalanced function and harmonics reduction function using zig-zag coils, and most of all, it is expected that the development of such high efficiency hybrid transformer possessing functions of transformation and reducing harmonics can improve the power quality as well as prevent damages caused by harmonics, leading to suppress unnecessary loss of electric power and thereby contribute to energy savings.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.7
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• pp.931-936
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• 2013

In this paper, the temperature distribution of 400kVA hybrid transformer is predicted by using CFD analysis. The copper loss and iron loss which are heat source are calculated by using Joule heat and Bertotti's equation respectively. To improve the convergence of the numerical calculation and to reduce the computation time, the 1/4 model is used and the incompressible air model is used for external air. To verify analysis result, the temperature rise test and no-load test of the transformer are performed. The experiment result obtained by using thermo-graphic camera is similar to the numerical result of the CFD analysis.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.355-359
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• 2000

This paper deal with the harmonic reduction technique in three-phase square-wave inverter system formed by single-phase inverter. To reduce the harmonics six single-phase inverters are used for forming multi-phase inverter and zig-zag connected output transformer for eliminating the harmonic 6(2k-1)$\pm$1 orders. And an ac filter is furnished at output side. Computer simulations show that the THD of the output voltage can be reduced immensely.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.258-260
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• 1995

This paper deals with the voltage unbalance of DC link voltage in series connected two 6-step inverters with double chopper preregulator. Each output of the 6-step inverter is connected to each transformer. The secondary windings of one of the transformers is zig-zag connected and the other star connected. The secondary terminals of the two transformers are series connected which makes 12-step output voltage waveform. In this case, the characteristics of the two transformers are rather different each other. The difference results in the voltage unbalance of the two 6-step inverter input capacitor voltages which make the DC link voltage. The degree of the voltage unbalance is analysied with the variations of load power, load power factor and % impedance of the transformer.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.987-988
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• 2011

산업발전과 전력용 반도체 소자의 비약적인 발달로 부하설비가 첨단화, 자동화 되면서 전력변환장치 등 비선형 부하 사용이 증가하고 있으며, 이에 따라 전력계통에는 고조파와 불평형이 필연적으로 발생하게 된다. 이러한 고조파와 불평형은 전력품질을 악화시킴으로써 설비의 효율 감소는 물론 전기적 사고와 불필요한 전력손실을 야기시키고 있다. 본 연구는 하이브리드변압기 동작원리 및 에너지절감 이론을 연구하고 실제 현장적용을 통한 에너지 절감효과 및 전력품질에 미치는 영향을 분석하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.54-60
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• 2004

With the proliferation of nonlinear loads such as commercial facilities in all of modern society high neutral harmonic currents have been observed. High neutral currents in three-phase four-wire distribution systems can cause lots of harmonic problems. The most common solution of neutral harmonic currents reduction is a zero phase sequence filter using zig-zag transformer. This paper analyzes a commercially available neutral line zero sequence currents reduction device and applies the equipment to commercial office loads for eliminating harmonics. Experimental results m compared numerically and graphically with simulation results through the use of MATLAB.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.3
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• pp.59-64
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• 2004

With the proliferation of nonlinear loads such as lighting facilities in all modern society high neutral harmonic currents have been observed. High neutral currents in three- phase four-wire distribution systems can cause lots of harmonic problems. The most common solution of neutral harmonic currents reduction is a zero phase sequence filter using zig-zag transformer. This paper analyzes a commercially available neutral line zero sequence currents reduction device and applies the equipment to lighting loads for eliminating harmonics. Experimental results are compared numerically and graphically with simulation results through the use of MATLAB.