• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.164-164
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• 2009

A multilayer piezoelectric transformer(MPT) for step-down voltage was made by ceramic stack process. And then, the characteristics of piezoelectric transformer, such as resonance frequency, matching impedance, electro-mechanical coupling coefficient, voltage gain, heat generation and efficiency, are analyzed. The piezoelectric transformer consists of a lead zirconate titanate ceramic with a high electromechanical quality factor. The piezoelectric transformer, with a multilayered construction in the thickness direction, was formed with dimensions 15mm long, 15mm wide and 5mm thick.

• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.350-356
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• 2006

In this study, piezoelectric transformer was manufactured at the sintering temperature of $950^{\circ}C$, and then the feasibility of application to low temperature sintering piezoelectric transformers was investigated by evaluating the electrical characteristics of it. The voltage ratio of piezoelectric transformer showed the maximum value at the resonant frequency of input part, and increased according to the increase of load resistance. The output power and efficiency of piezoelectric transformer showed the superior properties when the output impedance of it coincides with the load resistance. Piezoelectric transformer manufactured at the low temperature of $950^{\circ}C$ showed the heat generation less than $20^{\circ}C$ at the output power of 30 W, and stable driving characteristics.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.301-303
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• 2006

In this study, multilayer piezoelectric transformer were manufactured using the PZN-PMN-PZT ceramic and then the electrical characteristics were investigated. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value in the vicinity of 78.16kHz and increased according to the increase of load resistance. When the output impedance coincided with the load resistance, piezoelectric transformer showed the temperature increase of about $20^{\circ}C$ at the output power of 12W. The results, the multilayer transformer manufactured using the low temperature sintered PZN-PMN-PZT ceramics can be stably driven for step-up transformers.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.957-959
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• 2005

A noise reduction equipment in power systems was device combined in a passive element such as the form of L, R and C. A analysis of frequency characteristics for the transformer models shall be considered the additional capacitance between the windings($C_{ps}$), terminals($C_s$), and winding-ground($C_g$). A noise in transformer is modeled by take account into the different frequency. In case of the high frequency, transformer windings with stray capacitance have lower impedance. Therefore a noise is transferred from primary winding to secondary winding. Noise Cut Transformer(NCT) was the noise reduction device and was normally single phase two-winding type transformer. We analyzed frequency characteristics using the nodal network analysis with the equivalent circuit and the simulation of the MATLAB.

• 한국전기전자재료학회논문지
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• 제20권4호
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• pp.332-336
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• 2007

In this study, multilayer piezoelectric transformer was manufactured using the PMN-PNN-PZT ceramic and then the electrical characteristics were investigated according to the variations of frequency and load resistance. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value at the vicinity of 75 kHz and increased according to the increase of load resistance. When the output impedance coincided with the load resistance, the multilayer piezoelectric transformer showed the temperature rise of less than $20^{\circ}C$ at the output power of 20 W. As the results, the multilayer piezoelectric transformer manufactured at low co-firing temperature of $940^{\circ}C$ using PMN-PNN-PZT ceramics could be stably driven as the step-down transformers.

• 한국산학기술학회논문지
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• 제17권11호
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• pp.202-207
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• 2016

장대 터널 및 급곡선 구간과 같은 시계 확보가 어려운 지역에서 위험 및 안전 정보를 함께 공유하기 위해서는 기관사, 열차 관제사 및 현장 작업자 사이에 보조적인 실시간 열차 정보 통신시스템의 개발이 필요하다. 이에 적합한 열차 정보 통신시스템을 개발하기 위하여 본 연구에서는 작은 노이즈와 신호 감쇄를 동시에 갖도록 하는 레일 전력선 통신을 제안하였다. 이에 대한 레일 전력선 통신의 기초 연구 일환으로서, 본 통신기법의 전송 특성을 향상할 수 있는 레일에 대한 임피던스 측정 및 정합특성 평가가 중요하다. 본 연구에서는 자체 제작한 임피던스 정합 트랜스포머와 네트워크 분석기를 이용하여 레일에 대한 반사 및 전파 특성을 평가하였다. 대향 접속방식의 임피던스 반사특성 시험결과로부터 레일 전력선 통신에 적합한 정합용 트랜스포머의 정합비율은 1:3.28임을 알 수 있었다. 또한, 제작한 임피던스 정합용 트랜스포머는 레일 전력선통신에서 투과 신호 전송을 향상할 수 있음을 확인하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제9권1호
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• pp.67-71
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• 2007

HTS transformers which have been developed until now had only fundamental structures. Among the auxiliary functions of conventional transformers, voltage regulating is the most important one. For the voltage regulation, conventional transformers are equipped with on load tap changers (OLTCS). In this paper, we describe the possibility of the HTS transformer with OLTC. For the case study, we designed a single phase 33 MVA HTS transformer with OLTC. It is one of three individual HTS transformers which composes a 3 phase, 100 MVA transformer. It is expected to substitute for a 3 phase, 60 MVA conventional transformer in Korea. The parameters of an HTS transformer are varied due to the gap length between primary and secondary windings. The length was decided for the transformer to have the impedance of 12 %. Its size was limited to the one of the conventional transformer. The characteristics of the HTS transformer were analyzed in both case of having OLTC and not.

• 조명전기설비학회논문지
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• 제27권8호
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• pp.30-35
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• 2013

This paper describes the assessment method of deterioration condition for a power transformer using SFRA. Frequency Response Analysis(FRA) is a method to evaluate the mechanical and geometrical integrity of the core and windings within a power transformer by measuring the electrical transfer functions over a wide frequency range. SFRA is sweep frequency response analyzer for power transformer winding diagnosis. The FRA is a comparative method, that evaluates the transformer condition by comparing the obtained set of FRA results to reference results on the same, or a similar, unit. FRA techniques were widely used and much more sensitive than the traditional and internationally accepted method of impedance measurements, but that work was required on standardization and interpretation. In order to analyze the deterioration condition for power transformer, overvoltage test and mechanical distortion test were carried out. The deterioration condition for power transformer was evaluated by SFRA. It is intended to present the elemental technology of assessment method for power transformer using SFRA.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권8호
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• pp.394-400
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• 2001

This paper describes an application of the on line partial discharge measurement method in operating transformer. In the operating transformer, the partial discharge signal may be superimposed by radio intereference voltage(RIV) and pulse shaped noise signals generated by external corona. The partial discharge quantity showed about 3,800pC due to very high sinusoidal interferences at the measuring impedance terminal of the transformer bushing tap. In order to reject these noises, this paper applied RIV filter, band-pass filters and noise gating method. The resulting measuring sensitivity was improved from 3,800pC to 160pC.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.196-197
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• 2006

In this study, low temperature sintering multilayer piezoelectric transformer for DC-DC converter were manufactured using (PbCaSr)Ti(MnSb)$O_3$ ceramics and thin their electrical properties were investigated according to the vanation of frequency and load resistance. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value m the vicinity of 1.3MHz and increased according to the increase of load resistance. When the output impedance coincided with the load resistance, the piezoelectric transformer showed the temperature rise of about $21^{\circ}C$ under the output power of 6W.