• Title/Summary/Keyword: Single phase transformer

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Scott Transformer Modeling using Simulink on the AC Substation (Simulink를 이용한 교류 급전변전소의 스코트변압기 모델링)

  • Kim, Tae-Geun;Park, Young;Lee, Jong-Woo
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.2317-2322
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    • 2011
  • In three-phase power, when the power is supplied to the single phase load, there is the unbalance of load in the three-phase power. So the scott transformer is used in the power system to supply a single phase load in three-phase power without the unbalance of loads. Especially, the scott transformer is used in the AC substation of electric railroad. Two single phase transformers are combined by T-wiring in the scott transformer. So, two single phase voltage is provided by differing $90^{\circ}$ phase in three-phase power. The selection of related equipment and correction of protective relay are not easy from characteristic of the scott transformer when shunt and ground faults occur. In this paper, electric model of the scott transformer is suggested and the current of the scott transformer in shunt and ground faults is analyzed. Also, the scott transformer model is demonstrated by using Sinulink.

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Scott Transformer Modeling using PSIM on the AC Substation in the Elect ric Railroad (전기철도의 교류 급전변전소에서 PSIM을 이용한 스코트변압기 모델링)

  • Kim, Sung-Dae;Choi, Kyu-Hyoung
    • Proceedings of the KSR Conference
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    • 2010.06a
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    • pp.1892-1897
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    • 2010
  • In three-phase power, when the power is supplied to the single phase load, there is the unbalance of load in the three-phase power. So the scott transformer is used in the power system to supply a single phase load in three-phase power without the unbalance of loads. Especially, the scott transformer is used in the AC substation of electric railroad. Two single phase transformers are combined by T-wiring in the scott transformer. So, two single phase voltage is provided by differing $90^{\circ}$ phase in three-phase power. The selection of related equipment and correction of protective relay are not easy from characteristic of the scott transformer when shunt and ground faults occur. PSIM(Power Electronics Simulator) is optimal simulation software in field of the power electronics and provide the simple and convenient user interface. In this paper, electric model of the scott transformer is suggested and the current of the scott transformer in shunt and ground faults is analyzed. Also, the scott transformer model is demonstrated by using PSIM.

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A Technique for a Short-Circuit Current Calculation to The Single-Phase Transformer in the Three-Phase Systems (3상계통에서 단상변압기에 대한 단락전류계산 기법)

  • Park, Jae-Hwae;Jin, Tae-Seok
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.57 no.2
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    • pp.170-175
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    • 2008
  • This paper describes the exact short-circuit current calculation technique for the single-phase transformer which is installed in the three-phase systems and shorted in the secondary side. Not only the results for a short-circuit current calculation in the existing literatures are wrong, but also little literature deals with the short-circuit current for a single-phase transformer. So, this paper presents a theoretical study and calculation method for a single-phase short current. The validity of the presented method is investigated through Simulation using "Power Tools" and "PSim" program.

Characteristics of Utility Transformer on Household Single-Phase ESS-PCS According to LC Filter Location (주택용 단상 ESS-PCS의 LC 필터위치에 따른 상용변압기의 특성)

  • Kim, Yong-Jung;Kim, Hyosung
    • The Transactions of the Korean Institute of Power Electronics
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    • v.23 no.2
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    • pp.101-105
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    • 2018
  • Shortage of electric power occurs frequently along with increased electric power demand. ESS is a precaution to solve this issue. Household ESS has a capacity of approximately 3 kW/7 kWh. Household ESS batteries are typically designed with nominal voltages between 40 and 50 V. To connect household ESS with a 220 V AC system, low battery voltages in power conditioning system (PCS) should be boosted. To boost low battery voltage and match it with AC grid voltage, the use of a transformer for a commercial frequency can be considered. To attenuate switching harmonics of the household single-phase ESS-PCS, LC filter can be installed in two positions: on the primary side or on the secondary side of a transformer. A method has been used generally in single-phase inverters for the ESS-PCS. In another method, however, the output efficiency of the ESS-PCS may be decreased. Parasitic components of the transformer can affect voltage losses, when the square wave with the switching frequency in the ESS-PCS is passed through the transformer windings. In this work, the characteristics of the transformer according to the position of an LC filter are investigated for household single-phase ESS-PCS.

Single Phase NPC Module - Development of 75KVA Single Phase Smart Transformer with 3 Serial Cascade Configuration (단상 NPC Module- 3직렬 Cascade 구성 방식의 75KVA급 단상 지능형 변압기 개발)

  • Park, Ju-Young;Niyitegeka, Gedeon;Cho, Kyeong-Sig;Kim, Myung-Yong;Park, Ga-Woo
    • The Transactions of the Korean Institute of Power Electronics
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    • v.22 no.2
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    • pp.118-125
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    • 2017
  • In this paper, we propose a smart transformer for a smart transformer miniature model, which can replace a 60 [Hz] single-phase transformer installed in an electric vehicle. The proposed smart transformer is lighter than a conventional transformer, can control instantaneous voltage, and can be expected to improve power quality through harmonic compensation. The proposed intelligent transformer consists of an incoming part, an AC/DC converter, and a dual active bridge. Only the incoming part and the AC/DC converter are described in this paper. The proposed intelligent transformer has 75 kVA 3.3 kV input and 750 V DC output, which are verified by simulation and experiment.

Diagnosis of Fault and Abnormal Conditions in a Single-Phase Transformer Using S-parameter Measurement (S파라미터를 이용한 단상 변압기의 이상 상태 진단에 대한 연구)

  • Kim, Jeongeun;Kim, Kwangho;Nah, Wansoo
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.10
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    • pp.1344-1352
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    • 2018
  • In this paper, we propose a two-port S-parameter data to diagnose the fault conditions of a single-phase transformer. Using the S-parameters we can measure the reflection and transmission characteristics of signal power at the port of a transformer, which can also be converted into ABCD parameters and Z parameters through a well-known conversion formulas. Transformer fault diagnoses can be performed based on the intuitive and qualitative/quantitative characteristics of the these parameters. In addition, we can obtain wide frequency characteristics at the primary and secondary sides of the transformer, which can be used to get time domain responses using the inverse Fourier transformation with some specific input waveform. In order to verify the effectiveness of the proposed method, the fault conditions were analyzed in simulation and experiment for 3 kVA single phase transformer with 15: 5 turns ratio, and the validity of the proposed method was verified.

Conceptual Design of a Single Phase 33 MVA HTS Transformer with a Tertiary Winding (3차 권선을 고려한 단상 33MVA 고온초전도 변압기의 개념설계)

  • Lee, S.W.;Kim, W.S.;Hahn, S.Y.;Hwang, Y.I.;Choi, K.D.
    • Progress in Superconductivity
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    • v.7 no.2
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    • pp.162-166
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    • 2006
  • We have proposed a 3 phase, 100 MVA, 154 kV class HTS transformer substituting for a 60 MVA conventional transformer. The power transformer of 154 kV class has a tertiary winding besides primary and secondary windings. So the HTS transformer should have the 3rd superconducting winding. In this paper, we designed conceptually the structure of the superconducting windings of a single phase 33 MVA transformer. The electrical characteristics of the HTS transformer such as % impedance and AC loss vary with the arrangement of the windings and gaps between windings. We analyzed the effects of the winding parameters, evaluated the cost of each design, and proposed a suitable HTS transformer model for future power distribution system.

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Analysis of Reduction Effect of Three Harmonic Currents by Zigzag Wiring of Single Phase Transformer (단상 변압기 지그재그 결선에 의한 3고조파 전류 저감 효과 분석)

  • Kim, Jong-Gyeum;Kim, Ji-Myeong
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.66 no.3
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    • pp.99-104
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    • 2017
  • The three-phase four-wire power distribution system can be used to supply power to single-phase and three-phase loads at the same time. There are linear loads and nonlinear loads as single-phase loads connected to each phase. The nonlinear load generates a harmonic current during the power energy conversion process. In particular, the single-phase nonlinear load has a higher proportion of generation of the third harmonic current than the harmonics of the other orders. In a three-phase four-wire system, the third harmonic current flows through the neutral wire to the power supply side, affecting the power supply side and the line. Furthermore, the magnitude of the current flowing in the neutral line can be higher than the current flowing in the individual phase. If the neutral current is higher than the phase current, the breaker may be blocked. Therefore, it is necessary to reduce the amount of current flowing in the neutral line by harmonics. There is a method of zigzag connecting a single phase transformer by a method of reducing 3 harmonic current. In this study, the method of reducing the magnitude of the three harmonic currents flowing through the zigzag wire by comparing the polarity and the negative polarity characteristics of the single phase transformer was compared through measurement and simulation.

Transformer-Less Single-Phase Four-Level Inverter for PV System Applications

  • Yousofi-Darmian, Saeed;Barakati, Seyed Masoud
    • Journal of Power Electronics
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    • v.14 no.6
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    • pp.1233-1242
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    • 2014
  • A new inverter topology for single-phase photovoltaic (PV) systems is proposed in this study. The proposed inverter offers a four-level voltage in its output terminals. This feature results in easier filtering in comparison with other conventional two-level or three-level inverters. In addition, the proposed four-level inverter (PFLI) has a transformer-less topology, which decreases the size, weight, and cost of the entire system and increases the overall efficiency of the system. Although the inverter is transformer-less, it produces a negligible leakage ground current (LGC), which makes this inverter suitable for PV grid-connected applications. The performance of the proposed inverter is compared with that of a four-level neutral point clamped inverter (FLNPCI). Theoretical analysis and computer simulations verify that the PFLI topology is superior to FLNPCI in terms of efficiency and suitability for use in PV transformer-less systems.

Zero Sequence Impedance of Yg-Yg Three Phase Core Type Transformer (Yg-Yg 3상 내철형 변압기의 영상분 임피던스 분석)

  • Jo, Hyunsik;Cho, Sungwoo;Shin, Changhoon;Cha, Hanju
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.6
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    • pp.940-945
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    • 2016
  • In this paper, zero sequence equivalent circuit of Yg-Yg three phase core-type transformer is analyzed. Many problems by iron core structure of the three phase transformer due to asymmetric three phase lines, which includes line disconnection, ground fault, COS OFF, and unbalanced load are reported in the distribution system. To verify a feasibility of zero sequence impedance of Yg-Yg type three phase transformer, fault current generation in the three phase core and shell-type Yg-Yg transformer is compared by PSCAD/EMTDC when single line ground fault is occurred. As a result, shell-type transformer does not affect the flow of fault current, but core-type transformer generate an adverse effect by the zero sequence impedance. The adverse effect is explained by the zero sequence equivalent circuit of core-type transformer and Yg-Yg type three phase core-type transformer supplies a zero sequence fault current to the distribution system.