• Title/Summary/Keyword: low frequency transformer

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Development of Converter for High Frequency Welding Machines using Active Snubber (액티브 스너버를 이용한 고주파 용접기 컨버터 개발)

  • Shin, Jun-Young;Lee, Jae-Min;Choi, Seung-Won;Lee, Jun-Young
    • The Transactions of the Korean Institute of Power Electronics
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    • v.21 no.4
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    • pp.351-355
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    • 2016
  • Welding machines are high-capacity systems used in a low-frequency range using IGBT. As their system is similar to a large transformer, most welding machines suffer a great loss because of hard switching and vast leakage inductance. A voltage-balancing circuit is designed to overcome these shortcomings. This circuit can reduce the transformer size by making it into a high frequency and reducing the input voltage by half and by adopting a serial structure that connects two full-bridges in a series to use a MOSFET with a good property at high frequency. In addition, a Schottky diode is used in the primary rectifier to overcome the low efficiency of most welding machines. To use the Schottky diode with a reliably relatively low withstanding voltage, an active snubber is adopted to effectively limit the ringing voltage of the diode cut-off voltage.

High Efficiency and Small Size Switch Mode Line Transformer(SMLT) (고효율 및 소형 스위치모드 라인 트랜스포머)

  • Kim, Jin-Hong;Yang, Jung-Woo;Jang, Du-Hee;Kang, Jeong-Il;Han, Sang-Kyoo
    • The Transactions of the Korean Institute of Power Electronics
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    • v.24 no.4
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    • pp.237-243
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    • 2019
  • A high-efficiency and small-sized switched-mode line transformer (SMLT) is proposed in this study. The conventional structure of an adapter is composed of line transformer and rectifiers. This structure has a limit in miniaturizing due to low-frequency line transformer. Another structure is composed of power factor correction (PFC) and DC/DC converter. This structure has a limit in reducing volume due to two-stage structure. As the proposed SMLT is composed of an LLC resonant converter, a high-frequency transformer can be adopted to achieve isolation standards and size reduction. This proposed structure has different operation modes in accordance with line input voltage to overcome poor line regulation. In addition, the proposed SMLT is applied to the front of a conventional PFC converter, because the SMLT output voltage is restored to rectified sinusoidal wave by using a full-bridge rectifier in the secondary side. The design of the PFC converter is easy, because the SMLT output voltage is controlled as rectified sinusoidal wave. The validity of the proposed converter is proven through a 350 W prototype.

Effects of the Insulation Quality on the Frequency Response of Power Transformers

  • Abeywickrama Nilanga;Ekanayake Chandima;Serdyuk Yuriy V.;Gubanski Stanislaw M.
    • Journal of Electrical Engineering and Technology
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    • v.1 no.4
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    • pp.534-542
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    • 2006
  • This paper presents results of frequency domain spectroscopy (FDS) measurements on oil-impregnated pressboard insulation, their analyses and use of the data for modeling high frequency response (FRA) of transformers. The dielectric responses were measured in a broad frequency range, i.e. from 0.1 mHz to 1 MHz, on model samples containing different amount of moisture. The responses were parameterized with terms representing dc conductivity, low frequency dispersion and Cole-Cole polarization mechanisms and they were thereafter used to model the FRA response of a three-phase transformer.

Operating Characteristics in LCLC Resonant Converter with A Low Coupling Transformer. (낮은 커플링 변압기를 갖는 LCLC 공진컨버터 동작특성)

  • Kong Young-Su;Kim Eun-Soo;Lee Hyun-Kwan;Cho Jung-Goo;Kim Yoon-Ho
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.54 no.7
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    • pp.343-350
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    • 2005
  • Conventionally, for transferring the primary power to the secondary one, the high frequency series resonant converter has been widely used for the contactless power supply system. However, the high frequency series resonant converter has the disadvantages such as the low efficiency, the high voltage gain characteristics and deviation of the phase angle in the overall load range. To improve this disadvantages, In this paper, the characteristics of the high efficiency and unit voltage gain as well as in-phase are revealed in the proposed three-level LCLC (Inductor-Capacitor- Inductor-Capacitor) resonant converter. The results are verified on the simulation based on the theoretical analysis and the 4kW experimental Prototype.

A Transformer-less Boost Converter with High Gain and Low Current Ripple for Fuel Cell Application (연료전지 응용을 위한 높은 승압비와 낮은 전류리플을 갖는 무변압기형 부스트 컨버터)

  • Yang, Jin-Young;Park, Chan-Ki;Choi, Se-Wan;Nam, Seok-Woo
    • The Transactions of the Korean Institute of Power Electronics
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    • v.13 no.2
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    • pp.79-87
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    • 2008
  • Boost Converters have been used to step up and regulate the low and widely varing voltage from the fuel cell. A transformer-less boost converter which does not have lossy, bulky, and costly high frequency transformers has an advantage in applications where galvanic isolation is not required. In this paper a new transformer-less boost converter is proposed. The proposed boost converter has practically usuable 6 to 8 times of step up ratio and is suitable for fuel cell applications due to very low input and output current ripples. The proposed converter is verified through the theorical analysis, simulation and experimental waveform.

A Study on Pulse Power Suppuy for Microwave Oven Using HVC Embedded High Frequency Transformer (HVC 내장형 고주파변압기를 이용한 Microwave Oven용 펄스전원장치에 관한 연구)

  • Park K.H.;Cho J.S.;Jung B.H.;Mok H.S.;Park H.B.
    • Proceedings of the KIPE Conference
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    • 2001.07a
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    • pp.584-588
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    • 2001
  • A conventional power supply to drive a microwave oven has ferro-resonant transformer and high voltage Capacitor(HVC). Though it is simple, transformer is bulky, heavy and has low-efficiency. To improve this defect a high frequency inverter type power supply has been investigated and developed in recent years. But, because of additional control circuit and switching device, inverter-type power supply is more expensive than conventional one. In this study, A new pulse power supply for Microwave Oven using novel HVC embedded high frequency transformer is proposed for down-sizing, cost reduction, and efficiency emprovement of Inverter type power supply. Also, equivalent circuit model is derived by impedance measurements. And the operation of proposed pulse power supply is verified by simulations and experimental results.

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A Flyback Transformer linked Soft Switching PWM DC-DC Power Converter using Trapped Energy Recovery Passive Quasi-Resonant Snubbers with an Auxiliary Three-Winding Transformer

  • Ahmed Tarek;Chandhaket Srawouth;Nakaoka Mutsuo;Jung Song Hwa;Lee Hyun-Woo
    • Journal of Power Electronics
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    • v.4 no.4
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    • pp.237-245
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    • 2004
  • In this paper, a two-switch high frequency flyback transformer linked zero voltage soft switching PWM DC-DC power converter implemented for distributed DC- feeding power conditioning supplies is proposed and discussed. This switch mode power converter circuit is mainly based on two main active power semiconductor switches and a main flyback high frequency transformer linked DC-DC converter in which, two passive lossless quasi-resonant snubbers with pulse current regeneration loops for energy recovery to the DC supply voltages composed of a three winding auxiliary high frequency pulse transformer, auxiliary capacitors and auxiliary diodes for inductive energy recovery discharge blocking due to snubber capacitors are introduced to achieve zero voltage soft switching from light to full load conditions. It is clarified that the passive resonant snubber-assisted soft switching PWM DC-DC power converter has some advantages such as simple circuit configuration, low cost, simple control scheme, high efficiency and lowered noises due to the soft switching commutation. Its operating principle is also described using each mode equivalent circuit. To determine the optimum resonant snubber circuit parameters, some practical design considerations are discussed and evaluated in this paper. Moreover, through experimentation the practical effectiveness of the proposed soft switching PWM DC-DC power converter using IGBTs is evaluated and compared with a hard switching PWM DC-DC power converter.

A Study on Characteristics of Step-down Piezoelectric Transformer Using Transvers and Thickness Vibration mode (경방향과 두께방향 진동모드를 이용한 강압용 압전변압기의 특성에 관한 연구)

  • Chong, Hyon-Ho;Park, Tae-Gone;Kim, Myung-Ho;Kwon, O-Yong;Lee, Jin-I;Lee, Won-Jae
    • Proceedings of the KIEE Conference
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    • 2002.07c
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    • pp.1511-1514
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    • 2002
  • This paper presents design and construct of flat type step-down piezoelectric transformer for the application to AC adaptor. This piezoelectric transformer operated in resonance vibration mode. In this paper, finite element method(FEM) was used for analysing piezoelectric transformers. Stress and electric field of the transformer were simulated at resonance frequency. Using this simulation results, we manufactured improved Rosen type piezoelecric transfomer and measured its output characteristics. As results, output power was linearly increased by increasing input power at resonance frequency and it was found that the transformer an invariable output power for input power. From these results, we expect that this piezoelecric transfomer can be applied to small size and low capacitive AC adaptor.

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Digital Relaying Algorithm for Power Transformer Protection using Fuzzy Logic Approach

  • Park, Chul-Won;Shin, Myong-Chul
    • KIEE International Transactions on Power Engineering
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    • v.2A no.4
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    • pp.153-159
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    • 2002
  • Power transformer protective relay should block the tripping during magnetizing inrush and rapidly operate the tripping during internal faults. Recently, the frequency environment of power system has been made more complicated and the quantity of 2nd frequency component in inrush state has been decreased because of the improvement of core steel. And then, traditional approaches will likely be maloperate in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy based relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and percentage differential characteristic curve. The proposed relaying was tested with relaying signals obtained from EMTP simulation package and showed a fast and accurate trip operation.

A Miniaturized Broadband Impedance Transformer Employing Periodic Ground Structure for Application to Silicon RFIC (주기적 접지구조를 이용한 실리콘 RFIC용 광대역 소형 임피던스 변환기)

  • Young, Yun
    • Journal of Advanced Marine Engineering and Technology
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    • v.35 no.4
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    • pp.483-490
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    • 2011
  • Using a coplanar waveguide employing periodic ground structure (PGS) on silicon substrate, a highly miniaturized and broadband impedance transformer was developed for application to low impedance matching in broadband. Concretely, the multi-section transformer was designed using Chebyshev polynomials design technique for ultra broadband operation. Its size was 0.026 $m^2$ on silicon substrate, which was 8.7 % of the one fabricated by conventional coplanar waveguide on silicon substrate. The transformer showed a good RF performance over a ultra broadband from 8 - 49.5 GHz.