• Title/Summary/Keyword: Single-Phase transformer

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Output Waveform Improvement of Double-Connected 3-Phase Voltage Source Inverter by Single-Phase Inverter (단상 인버터의 동작에 의한 이중접속 3상 전압원 인버터의 출력파형 개선)

  • 최세완
    • Proceedings of the KIPE Conference
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    • 2000.07a
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    • pp.330-334
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    • 2000
  • This paper proposes a new double-connected 3-phase voltage source inverter with improved output voltage waveform. An auxiliary single-phase inverter injects a ripple voltage into the double- connected inverter to convert 12-step operation to 36-step operation. The KVA rating of the output phase-shifting transformer is reduced by employing a harmonic canceling reactor. The whole rectifier-inverter system including the proposed technique is introduced and the experimental results are provided.

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Series Compensated Step-down AC Voltage Regulator using AC Chopper with Transformer

  • Ryoo, H.J.;Kim, J.S.;Rim, G.H.
    • KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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    • v.5B no.3
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    • pp.277-282
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    • 2005
  • This paper describes a step-down AC voltage regulator using an AC chopper and auxiliary transformer, which is a series connected to the main input. The detail design of the AC regulator, logic and PWM pattern of the AC chopper is described and the three-phase AC regulator using two single­phase AC choppers with a three transformer configuration is proposed for three-phase application. The proposed three-phase system has the advantages of lower system cost due to reduced switch number and gate driver circuit as well as advantages of decreased size and weight because it uses a series compensated scheme. The proposed AC regulator has many benefits such as fast voltage control, high efficiency and simple control logic. Experimental results indicate that it can be used as a step-down AC voltage regulator for power saving purposes very efficiently.

The conceptual design and analysts of three phase superconducting fault current limiter (일체형 삼상 고온 초전도 한류기의 단락 특성 해석)

  • Lee, Sueng-Je;Lee, Chan-Joo;Lee, Chang-Yul;Jang, My-Hye;Ko, Tae-Kuk
    • Proceedings of the KIEE Conference
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    • 1998.07a
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    • pp.94-97
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    • 1998
  • The conceptual design of integrated three phase superconducting fault current limiter (SFCL) is presented. And through simulation of power system where this SFCL is installed, the characteristics of this SFCL is analyzed. It is like three-phase transformer. So it has the same characteristics with inductive single phase SFCL. But it has more merits than single phase SFCL. Differently to single phase SFCL, integrated three phase SFCL induces impedance at all phase by any single phase fault to protect the power system more safely.

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Basic Modeling and Analysis for AC Railway System based on BTB Voltage Source Converter (BTB 전압형 컨버터 기반의 전기철도 급전변전 시스템의 기본 모델링 및 해석)

  • Yoo, Hyeong-Jun;Kim, Hak-Man;Jung, Ho-Sung
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.11
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    • pp.1737-1742
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    • 2012
  • The scott transformer is used to supply single-phase power to the AC railway system. Since the scott transformer is a passive facility, it cannot regulate load-side voltage according to load change. Meanwhile, the Voltage Source Converter (VSC) is able to convert the voltage and control active and reactive power. In this paper, the feasibility of a AC railway system based on Back-to-Back (BTB) VSC which is composed of a rectifier, a DC-DC converter, a inverter, has been proposed. A three-phase to single-phase BTB VSC is modeled. The proposed AC railway system based on BTB VSC is tested on Matlab/Simulink.

Transformer-less Type Grid-Connected PV Power Conditioning System (변압기 없는 계통연계형 PV PCS고찰)

  • Jung, Young-Seok;Yu, Gwon-Jong;Jung, Myoung-Woong;Choi, Jae-Ho;Choi, Ju-Yeop
    • Proceedings of the KIPE Conference
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    • 2002.07a
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    • pp.551-554
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    • 2002
  • This paper describes a new interactive inverter between a photovoltaic(PV) array and single-phase utility that avoid the bulky input (60Hz) transformer on the AC side. The interface employs a pwm boost converter on the DC side followed by a pwm current-forced single-phase rectifier for injecting the power from the PV array into the mains. The current waveform at the AC side remains sinusoidal and exactly in phase at all time. The circuit also has the advantage of requiring fewer switching device than high-frequency link system. This paper describes modeling of PV array and new system topology. Simulation results on the performance of the connection are also presented.

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Design of a IMVA Single-Phase HTS Power Transformer

  • Kim, Sung-Hoon;Kim, Woo-Seok;Park, Chan-Bae;Hahn, Song-yop;Park, Kyeong-Dal;Joo, Hyeong-Gil;Hong, Gye-Won
    • Progress in Superconductivity
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    • v.4 no.1
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    • pp.86-89
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    • 2002
  • In this paper, the design of a IMVA single-phase high temperature superconducting(HTS) power transformer with BSCCO-2223 HTS tapes is presented. The rated voltages of each sides of the transformer are 22.9 ㎸ and 6.6 ㎸, respectively The winding of 1MVA HTS transformer is consisted of double pancake type HTS windings, which have advantages of insulation and distribution of high voltage, and are cooled by subcooled liquid nitrogen of 65K. Four HTS tapes were wound in parallel for the windings of low voltage side and the four parallel conductors are transposed. The design of 1MVA HTS transformer, a shell type core made of laminated silicon steel plate is chosen, and the core is separated with the windings by a cryostat with a room temperature bore. The cryostat made of non-magnetic and non-conducting material and a liquid nitrogen sub-cooling system is designed in order to maintain the coolant's temperature of 65K. For electromagnetic analysis of 1MVA HTS transformer, a finite element method of an axis of symmetry is used. The maximum perpendicular component of magnetic flux density of pancake windings is about 0.15T. And through analyzing the magnetic field distribution, an optimal winding arrangement of 1MVA HTS transformer is obtained.

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Structure and Control of Smart Transformer with Single-Phase Three-Level H-Bridge Cascade Converter for Railway Traction System (Three-Level H-Bridge 컨버터를 이용한 철도차량용 지능형 변압기의 구조 및 제어)

  • Kim, Sungmin;Lee, Seung-Hwan;Kim, Myung-Yong
    • Journal of the Korean Society for Railway
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    • v.19 no.5
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    • pp.617-628
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    • 2016
  • This paper proposes the structure of a smart transformer to improve the performance of the 60Hz main power transformer for rolling stock. The proposed smart transformer is a kind of solid state transformer that consists of semiconductor switching devices and high frequency transformers. This smart transformer would have smaller size than the conventional 60Hz main transformer for rolling stock, making it possible to operate AC electrified track efficiently by power factor control. The proposed structure employs a cascade H-Bridge converter to interface with the high voltage AC single phase grid as the rectifier part. Each H-Bridge converter in the rectifier part is connected by a Dual-Active-Bridge (DAB) converter to generate an isolated low voltage DC output source of the system. Because the AC voltage in the train system is a kind of medium voltage, the number of the modules would be several tens. To control the entire smart transformer, the inner DC voltage of the modules, the AC input current, and the output DC voltage must be controlled instantaneously. In this paper, a control algorithm to operate the proposed structure is suggested and confirmed through computer simulation.

A Study on the Vibration Reduction of the SPR(sudden pressure relay) in the Single Phase Main Power Transformers(345kV) (단상(345kV) 주변압기 압력 계전기의 진동절연에 관한 연구)

  • Park, Chul-Jun;Lee, Seong-Wook;Choi, Won-Ho;Lee, Wook-Ryun;Kweon, Ki-Young
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.5
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    • pp.486-491
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    • 2010
  • In this paper, it is identified that high-level vibration of the single phase main power transformers shut down due to the mechanical fault. vibration sources of the SPR in the transformer's are identified and the SPR vibrations are reduced by structural modification. For vibration characteristic identification, vibration signals were measured with an accelerometer when the transformer is driving. These signals are presented in a FFT analysis in order to find the dependency of frequency components on the transformer. From finite element analyses and some experiments, it is also found that resonances occur because the natural frequencies of the SPR exist in usual driving range. To shift the natural frequencies outside the driving range, the SPR is modified by increasing stiffness. It is verified that considerable amounts of vibration are reduced by the structural modification.

Analysis for the Ferroresonance on the Transformer by Overvoltage and Prevention Measures (과전압에 의한 변압기 철공진 분석 및 방지대책)

  • Yun, Dong-Hyun;Shin, Dong-Yeol;Cha, Han-Ju
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.64 no.11
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    • pp.1543-1550
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    • 2015
  • Ferroresonance is a non-linear vibrational phenomenon that is generated by the electrical interaction of the inductance component with the capacitor component of a certain capacitance as the device of the inductance component such as a transformer is saturated due to the degradation, the waveform distortion of current and voltage, and the oscillation of overcurrent and overvoltage in a system. Recently, ferroresonance was generated from the waveform distortion of current and voltage, or the overvoltage or undervoltage phenomenon caused by the nature of an electrical power system and design technology of the transformer in the three phase transformer system. Hence, in general, ferroresonance analyzed by converting to the LC equivalent circuit. However, in general, the aforementioned analytical method only applies to the resonance phenomenon that is generated by the interaction of the capacitance of bussbar and grounding, and switching as the capacitor component with PT and the transformer as the inductance component in a system. Subsequently, the condition where ferroresonance was generated since overvoltage was supplied as line voltage to the phase voltage and thus the iron core is saturated due to the interconnection between grounded and ungrounded systems could not be analyzed when single phase PT was connected in a ${\Delta}$/Y connection system. In this study, voltage swell in the configuration of grounded circuit of a step-up transformer with the ${\Delta}-{\Delta}$ connection linked to PT for control power and the ferroresonance generated by overvoltage when the line voltage of the ${\Delta}-{\Delta}$ connection was connected to the phase voltage of the grounded Y-Y connection were analyzed using PSCAD / EMTDC through the failure case of the transformer caused by ferroresonance in the system with the ${\Delta}-{\Delta}$/Y-Y connection, and subsequently, the preventive measure of ferroresonance was proposed.