• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권6호
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• pp.324-329
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• 2004

Six stator slot couplers(SSC) and a flux probe sensor installed on the stator winding slots of large turbine generator. Assessment of insulation condition has been based upon the measurements of partial discharge(PD) of stator windings and shorted-turn of rotor windings in operating large turbine generator. The maximum PD magnitude(Qm), normalized quantify number(NQN), PD pattern and shorted-turn were measured using on-line insulation condition monitoring system. The NQN and Qm of slot PD side in the phase A are indicated the highest value in six SSC sensors. Monitoring system results showed that discharge at conductor surface and internal discharge were detected at the surface of stator winding and in voids of the groundwall insulation. Insulation of stator and rotor windings in large turbine generator was judged to be in good condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.134-136
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• 1995

A superconducting parallel bifilar winding shows the phenomenon which is known as 'fast quench'. We analyzed the temperature characteristics on the winding by computer simulation, and confirmed theses by experiment. The temperature of the quenched point rose gradually as the source voltage was increased. The temperature changed radically as first, but had a gentle slope after a few milliseconds. As the source voltage was large, the initial quenched length also increased. The points in this quenched length showed almost the same temperature. but the points where initial quench had not occurred showed radical temperature gradient. We could observe that the temperature of the whole wire increased simultaneously as the fast quench occurred on the superconducting parallel bifilar winding, because a number of quenched points in that wire appeared at the same time.

• 한국추진공학회지
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• 제3권2호
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• pp.56-65
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• 1999

본 연구에서는 와인딩시 공정조건의 변화가 필라멘트와인딩 복합재의 기계적 특성에 미치는 영향을 조사하였다. 와인딩시의 공정변수로는 섬유장력과 섬유엔드수를 고려하였다. 고려한 시편은 필라멘트와인딩 공법으로 제작된 링 시편으로 강화섬유는 TZ-507 탄소섬유와 IZ-40 탄소섬유를 사용하고 수지는 필라멘트와인딩용 에폭시를 사용하였다. 와인딩시 섬유장력은 0.5kgf에서 3.0kgf의 범위에서 변화시켰으며 섬유엔드수는 1엔드에서 6엔드의 범위에 서 변화시켰다. 와인딩시 섬유장력과 섬유엔드수를 변화시킨 링 시편의 섬유체적비와 기공함유율은 황산용해법을 적용하여 측정하였으며 이들 링 시편의 기계적 특성은 스프릿 디스크 시험을 통해 평가하였다. 본 연구의 수행을 통해 얻어진 결과들로 판단하면 와인딩시 섬유 장력과 섬유엔드수는 필라멘트와인딩 복합재의 섬유체적비와 기공함유율을 변화시킬 뿐 아니라 필라멘트 와인딩 복합재의 기계적 특성에도 밀접한 영향을 미친다. 따라서 필라멘트와인딩 복합재의 구조성능을 극대화하고 생산성을 향상시키기 위해서는 최적의 필라멘트 와인딩 공정조건이 적용되어야 한다.

• 비파괴검사학회지
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• 제32권1호
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• pp.64-70
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• 2012

국내 원자력발전소 증기발생기 전열관의 건전성을 평가하기 위해서 수행되는 와전류검사의 탐촉자는 주로 두가지 종류가 사용한다. 첫 번째 와전류탐촉자는 마모와 같은 체적성 결함을 검사하기 위해 사용되는 보빈탐촉자이다. 두 번째 와전류탐촉자는 균열과 같은 비체적성 결함을 검사하기 위한 회전형 탐촉자이다. 와전류탐촉자는 검사 계통의 핵심적인 부분으로서 특정 절차서에 따라 평가가 이루어질 때 대상 시험체의 합부를 결정하는 자료를 제공하게 된다. 또한, 수집된 와전류신호의 품질은 사용되는 탐촉자의 설계특성, 기하학적 형태, 운전주파수에 따라 결정되고, 검사 결과에 미치는 영향이 크기 때문에 와전류검사 탐촉자의 선정은 특히 중요하다. 본 연구에서는 차동형 보빈탐촉자의 코일 권선 수의 변화가 탐촉자의 전기적 특성에 미치는 영향을 분석하였다. 이 결과를 이용하여 원전 증기발생기 전열관 와전류검사 보빈탐촉자를 설계하였다. 연구 결과 코일 권선 수의 변화는 전열관 형상 및 재질에 따른 검사주파수 선정에 크게 영향이 미침을 알 수 있다. 따라서 본 연구 결과를 통하여 원전 증기발생기 전열관 와전류검사 보빈탐촉자의 설계시 더욱 정밀한 코일 권선 수 설정에 토대를 구축하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2310-2316
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• 2011

In order to apply Interior Permanet Magnet Synchronous Motor(IPMSM) to the propulsion system of the railway transit, 110 (kW) class IPMSMs with high-power density are designed as a concentrated winding model and a distributed winding model in this study. The concentrated winding model designed in this study is 6 poles/9 slots and the distributed winding model is 6 poles/36 slots. In general, the eddy current losses in the permanent magnets of IPMSM are caused by the slot harmonics. The thermal demagnetization of the magnet by the eddy current losses at high rotational speed often becomes one of the major problems in the IPMSM with a concentrated windings especially. A design to reduce eddy current losses in permanent magnets design is important in IPMSM for the railway vehicle propulsion system which requires high-speed operation. Therefore, a method to devide the permanent magnet is proposed to reduce the eddy current losses in permanent magnet in this study. Authors analyze the variation characteristics of the eddy current losses generated in permanent magnet of the concentrated winding model by changing the number of the division of the permanent magnets.

• Journal of Magnetics
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• 제21권3호
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• pp.431-436
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• 2016

In the design of transformer winding, natural vibration frequency is an important parameter. This paper presents a 2D model to calculate axial vibration natural frequency of power transformer winding based on the elastic dynamics theory, and according to the elastic support equivalent principle of radial pressboards. The 3D model to calculate natural vibration frequency can be simplified as a 2D one as the support of pressboards on the winding is same. It is verified that results of the 2D model are consistent with those of 3D one, but the former can achieve much higher calculation efficiency. It shows that increasing the width and number of pressboards can improve axial natural frequency through formula analysis and simulation, and also the relations between the changes of axial pre-compression and axial natural vibration frequency on the windings are investigated. Finally, the proposed 2D model's effectiveness is proved when compared with tested ones.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.367-376
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• 2016

This paper presents a cell balancing method for a single switch flyback converter with a multi-winding transformer. The conventional method using a flyback converter with a multi-winding transformer is simple and easy to control, but the voltage of each secondary winding coil might be non-uniform because of the unequal effective turn-ratio. In particular, it is difficult to control the non-uniform effect using turn-ratios because secondary coil has a limited number of turns. The non-uniform secondary voltages disturb the cell balancing procedure and induce an unbalance in cell voltages. Individual cell control by adding a switch for each cell can reduce the undesirable effect. However, the circuit becomes bulky, resulting in additional loss. The proposed method here uses the conventional flyback converter with an adjustment made to the output filters of the cells, instead of the additional switch. The magnitude of voltage applied to a particular cell can be reduced or increased according to the adjusted filter and the selected switching frequency. An analysis of the conventional converter configuration and the filter design method reveals the possibility of adequate cell balancing control without any additional switch on the secondary side.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권11호
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• pp.547-554
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• 2006

The detent force of a permanent magnet linear motor(PMLM) consists of the end force and cogging force, and should be reduced for high precision purpose applications. The cogging force comes from the electromagnetic interaction between the permanent magnets and interior teeth(or the slots) of the stator, and of which the magnitude depends on the ratio of the numbers of the armature and permanent magnet poles as well as the geometrical shape of the permanent magnet and armature pole. In order to reduce the cogging force of a PMLM, this paper proposes a new configuration which has 9 permanent magnet poles and 10 armature winding slots. By theoretical investigation of the principle of cogging force generation and simulating using finite element method, the proposed PMLM configuration is proven to give much less cogging force than the conventional configuration which has 8 permanent magnet poles and 12 armature winding slots. A proper winding algorithm, modified (A, A, A) winding method, for the proposed configuration is also suggested when the proposed PMLM is operating as a 3 phase synchronous machine. A theoretical and numerical calculation shows that the proposed configuration makes slightly bigger back-emf and thrust force under same exciting current and total number of winding turns condition.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권3호
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• pp.101-106
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• 2003

The high temperature superconductor transformers gain interests from the industries. This paper described construction and test results of 10㎸A HTS transformer Three phase transformer with double pancake windings were constructed. To reduce the leakage magnetic field, secondary coil were placed between the two primary coils. BSCCO-2223 wire. silicon sheet steel core and FRP cryostats were used to construct the transformer. Three coils were stacked in one cryostat. Two double pancake coils were connected in series for the primary coil and one double pancake coil was used for the secondary coil. Total number of turns of the primary winding and the secondary winding were 112turns and 98urns, respectively, The rated voltages of each winding were 440/220V. The rated currents of each winding were 13.1/26.2A. After the tests of basic properties of the three phase HTS transformer using no-load test, short-circuit test and full-load test, continuous operation of 100 hours with pure resistive load has been carried out. Test results proved over-load capability and reliability of the HTS transformer.

• 전자공학회논문지SC
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• 제40권5호
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• pp.350-354
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• 2003

본 논문에서는 능동 클램프 스위치를 위한 별도의 구동 회로가 생략된 새로운 자기 구동 능동 클램프 포워드 컨버터를 제안하였다. 능동 클램프 스위치의 구동에는 컨버터 자체의 변압기의 보조 권선을 이용하였고, 두 스위치 구동 신호 사이의 데드 타임을 설정하기 위하여 간단한 R-C지연 회로를 추가하였다. 제안된 컨버터의 동작 원리를 제시하였고 실험 결과를 가지고 이론적인 결과를 입증하였다. 출력 100W(5V/20A)의 컨버터를 제작하였으며 입력이 50V일 때 능동 클램프 스위치의 구동에 단지 1.5T의 보조 권선의 권선수로 충분하다는 점을 보였다. 끝으로 제안된 컨버터의 측정 효율을 제시하였고 91%의 최대 효율을 달성하였다.