• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.5
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• pp.545-550
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• 2012

Steam generator is one of the major components of nuclear power plant and steam generator tubes are the pressure boundary between primary and secondary side, which makes them critical for nuclear safety. As the operating time of nuclear power plant increases, not only damage mechanisms but also scaled deposits on steam generator tubes are known to be problematic causing tube support flow hole blockage and heat fouling. The ability to assess the extent and location of scaled deposits on tubes became essential for management and maintenance of steam generator and eddy current bobbin data can be utilized to measure thickness of scale on tubes. In this paper, tube reference standards with various thickness of scaled deposit has been set up to provide information about the overall deposit condition of steam generator tubes, providing essential tool for steam generator management and maintenance to predict and prevent future damages. Also, methodology to automatically measure scale thickness on tubes has been developed and applied to field data to estimate overall scale amount.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.1
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• pp.64-70
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• 2012

Two kinds of eddy current probes are mainly used to perform the steam generator tube integrity assesment in NPPs. The first one is the bobbin probe using for inspection of volumetric defect like a fretting wear. The second one is the rotating probe using for inspection of non-volumetric defect like a crack. The eddy current probe is one of the essential components which consist of the whole eddy current examination system, and provides a decisive data for the tube integrity in accordance with acceptance criteria described in specific procedures. The design of ECT probe is especially important to improve examination results because the quality of acquired ECT data is depended on the probe design characteristics, such as coil geometry, electrical properties, operation frequency. In this study, it is analyzed that the coil winding number of differential bobbin probe affects the electrical properties of the probe. Eddy current bobbin probes for the steam generator tubes in NPPs are designed and fabricated according to the results. Experiment shows that the change in coil winding number has much effects on the optimum inspection frequency determined by the tube geometry and material. Therefore, the coil winding number in bobbin probe is very important in the probe design. In this study, a basis of the coil winding number for the eddy current bobbin probe design for steam generator tubes in NPPs is established.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.138-141
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• 1999

전류의 손실 없이 MRI 마그네트의 연구전류 운전을 위한 영구전류스위치(Persistent Current Switch;PCS)를 설계 및 제작하여 그 특성을 측정하였다. 한국전기연구소의 Whole body MRI 마그네트로의 적용을 위해 설계되었으며, 또한 PCS 보빈을 기존의 FRP에 비해 열전도 특성과 기계적 강도가 우수한 알루미늄으로 제작하였다. Main 코일 1개와 Shim 코일 9개의 PCS에 대한 필요한 파라미터를 계산하여 제작하였다. PCS의 기본요구조건인 step 형태의 스위칭 특성과 각 PCS가 실온저항의 50%∼55%의 상전도 저항 특성을 보임을 확인하였다.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.48-50
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• 2003

개폐형(On/Off) 솔레노이드 액츄에이터의 설계에서는 온도상승을 고려한 권선수 산출이 가장 중요하고, 제작과정에서는 설계단계에서 산출된 권선수를 정확하게 정렬권선 형태로 구현해 내는 것이 가장 중요하다. 본 연구에서는, 비 정렬권선이 개폐식 솔레노이드 액츄에이터의 동작에 미치는 영향을 실험적으로 분석하였다. 실험은 하나의 정렬권선 코일과 비 정렬 상태가 다른 세권선을 사용하여 보빈과 연결된 요크가 있는 경우와 없는 경우를 각각 실험하고 그 때의 흡인력 온도상승 소비전력 등의 특성을 비교하였다. 특히, 온도상승 실험은 실제 사용시의 상황을 구현하기 위하여 권선상태가 다른 4종류의 코일 각각에 100만회의 내구성 시험을 실시하면서 작동횟수를 등분하여 코일, 요크, 몰딩부의 각 측정점 온도를 측정하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.1
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• pp.53-58
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• 2001

The main noise sources in SMPS are divided into three parts: the switching devices, the rectifiers in secondary part, the output transformer and choke coil. In this paper we performed the noise analysis with respect to bobbin type and winding method, and designed an optimized transformer focusing on the transformer. For the comparison. we measured four parameters for each cases, including EMI conducted emission noise. signal from the switching devices, output ripple/noise voltage and leakage current. As the result, the transformer using a vertically-typed bobbin and a parallel, sandwich winding method showed the best performance. We confirmed that the SMPS developed in this research is satisfied with the IEC 601-1 international standard for the medical instrumentation. by testing its electrical characteristics and safety.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2623-2627
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• 2014

The objective of this study is to experimentally investigate the heat transfer characteristics of 200W woofer speaker unit with the input voice signals such as 500 Hz, 1000 Hz, 2000 Hz, and 3000 Hz. The temperature and heat transfer characteristics of the woofer speaker unit were evaluated with the input signals. As results. the temperature of the voice-coil for woofer speaker unit increased with a decrease of the input signals and the temperature differences between parts of the tested speaker unit increased with the decrease of the input voice signals. In addition, the voice-coil temperature for the input signal of 500 Hz showed 48.4 % lower than that of 3000 Hz during 18000 sec.

• Journal of IKEEE
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• v.22 no.1
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• pp.185-188
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• 2018

This paper describes the parasitic capacitance modeling according to the coil structure, section bobbin and winding method for hybrid choke coil with reduced parasitic capacitance capable of the EMI attenuation of broad bands from lower frequency to higher frequency applied in the EMI attenuation filter of LED-TV SMPS. Especially, the hybrid choke coil with reduced parasitic capacitance($C_p$) proposed in this paper can reduces the parasitic capacitance($C_p$) by adopting the winding methods of rectangular copper wire, compared to the conventional common mode choke coil with the winding method of automatic type. The first resonant frequency of the proposed hybrid choke coil has a tendency to increase as the parasitic capacitance is smaller and its impedance characteristics, especially in the high frequency bands, improves as the first resonant frequency increases. In the future, the proposed hybrid choke coil with reduced parasitic capacitance shows it can be actually utilized in not only LED-TV SMPS but also various applications such as LED Lighting, Note-PC Adapter, and so forth.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.184-190
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• 2008

Various ECT techniques have been applied basically to assess the integrity of steam generator tithing in nuclear power plant. Among these techniques, the bobbin probe technique is applied generally to examine the volumetric flaws such as a crack-like defect and wear which is generally occurred on steam generator tubing, and additionally MRPC probe is used to examine closely tile top of tubesheet and bending regions due to the high possibility of cracking. Dent and bulge also may be formed on tube during installation process and operation of steam generator, but the dent and bulge indications greater than specific size criteria are recorded on examination report because these indications are not considered as flaw. These indications can be easily detected with bobbin probe and approximately sized with profile bobbin probe, but the size and shape can not be accurately verified. Accordingly, in this study, the $8{\times}1$ multi-array EC probe was designed to increase the measurement accuracy of the sectional profiling EC testing of tube. As a result, we would like to propose the application of $8{\times}1$ multi-array EC probe for the measurement of size and shape of profile change on steam generator tube in OPR-1000 nuclear power plant.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.2
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• pp.89-96
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• 2007

The bobbin probe examination is basic and the important method among other ECT techniques for the steam generator tube integrity assesment that is practiced during each plant outage. The bobbin probe is one of the essential components which consist of the whole ECT examination system, and provides us a decisive data for the evaluation of tube integrity in compliance with acceptance criteria described in specific procedures. The selection of examination probe is especially important because the quality of acquired ECT data is determined by the probe design characteristics, such as geometry and operation frequency, and has enormous effects on examination results. In this study, An optimal differential bobbin probe is designed for the steam generator tube inspection in nuclear power plants(NPPs). Based on the test results for electrical and ECT signal characteristics, the prototype bobbin probe satisfies all the criteria.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.475-482
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• 2014

The precision hydraulic valve is widely used in various industrial field like aircraft, automobile, and general machinery. Servo actuator is the most important device for driving the precise hydraulic valve. The reliable operation of servo actuator effects on the overall hydraulic system. The performance of servo actuator relies on frequency response and step response according to arbitrary input signal. In this paper, we performed the analysis for the components of servo actuator to satisfy the reliable operation and response characteristics through the reliability analysis, and also induced the design parameters to realize the reliable operation and fast response characteristics of servo actuator for hydraulic valve operation through the empirical knowledge of experts and electromagnetic theories. We suggested the design equations to determine the values of design parameters of servo actuator as like bobbin size, length of yoke and plunger and turn number of coil, and verified the achieved design values through FEM analysis and performance tests using some prototypes of servo actuators adapted in hydraulic valve.