• Title/Summary/Keyword: Differential Coil

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Simulation of ECT Bobbin Coil Probe Signals to Determine Optimum Coil Gap

  • Kong, Young-Bae;Song, Sung-Jin;Kim, Chang-Hwan;Yu, Hyung-Ju;Nam, Min-Woo;Jee, Dong-Hyun;Lee, Hee-Jong
    • Journal of the Korean Society for Nondestructive Testing
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    • v.26 no.6
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    • pp.403-410
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    • 2006
  • Eddy current testing (ECT) signals produced by a differential bobbin coil probe vary according to probe design parameters such as the number of turns, geometry and coil gap size. In the present study, the characteristics of a differential bobbin coil probe signals are investigated by numerical simulation in order to determine the optimum coil gap. For verification of numerical simulation accuracy, a specially designed bobbin probe of which the coil gap can be adjusted is fabricated and a series of experiments to acquire signals from two kinds of standard tubes with the variation in coil gap is performed. Then, the experimental signals are compared to the simulation results. Based on this investigation, a decision on the optimum range of coil gap is made. The theoretically predicted signals agree very well to the experimental signals. In fact, this excellent agreement demonstrates a high potential of the simulation as a design optimization tool for ECT bobbin probes.

A Study for measuring the Intial Permeability of Soft-Ferrite Powder by Using Differential Transformer Coil (차동트랜스 코일을 이용한 Soft-Ferrite 분말의 초투자율측정에 관한 연구)

  • Jun, Hong-Bae;Heo, Jin;Kim, Chul-Han;SaGong, Geon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.04b
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    • pp.68-71
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    • 2000
  • In this study, A set-up for measuring a initial permeability of soft-ferrite powder was developed with a differential transformer coil. To measure a initial permeability of magnetic powder is cumbersome since there are not any measuring equipment and method. A magnetic powder is currently used for a magnetic fluid and microwave absorber materials, and the initial permeability of the magnetic powders is very important to be evaluated a powder for some applications.

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Construction of Differential Type Search Coil Magnetometer (차동형 탐지코일 마그네토미터 제작)

  • Kim, J.H.;Son, De-Rac
    • Journal of the Korean Magnetics Society
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    • v.20 no.5
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    • pp.178-181
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    • 2010
  • Search coil magnetometer has been used for detection of ac magnetic field with high sensitivity. To reduce demagnetizing factor of core and increase S/N ratio of search coil magnetometer, the core was divided by two parts and coil was wound on each cores. Two coils were connected serially and put into amplifier as differential mode. Constructed 120 mm length search coil magnetometer shows linearity of 0.03%, sensitivity of 9.3 mV/nT, and resolution of 20 pT at 1 Hz.

"Leak Current" correction for critical current measurement of no-insulation HTS coil

  • Song, Jung-Bin;Hahn, Seungyong
    • Progress in Superconductivity and Cryogenics
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    • v.19 no.2
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    • pp.48-52
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    • 2017
  • Discrepancy between a power supply current and an actual "spiral" coil current makes the conventional 4-probe measurement of a critical current ($I_c$) of a no-insulation (NI) high temperature superconductor (HTS) coil inaccurate and time-consuming. This paper presents a fast and accurate approach for $I_c$ measurement of NI HTS coils. With an NI HTS coil energized at a constant ramping rate, a complete analytic expression for the spiral coil current was obtained from a first-order partial differential equation that derived from an equivalent circuit model of the NI coil. From the analytic solution, both spiral coil current and radial leak current can be obtained simultaneously, which enables fast and accurate measurement of the NI coil $I_c$. To verify the proposed approach, an NI double-pancake (DP) coil, wound with GdBCO tapes of $6mm{\times}0.1mm$, was constructed and its $I_c$ was repeatedly measured with various ramping rates in a bath of liquid nitrogen at 77 K. The measured results agreed well with the calculated ones, which validates the proposed approach to measure $I_c$ of an NI HTS coil.

A Flow Quantity Distribution Characteristics of the Hot Water Header for Individual Room Control System (실별제어 온수분배기의 유량분배 특성)

  • Sung, Sun-Kyung
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.3
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    • pp.175-180
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    • 2008
  • Flow quantity to supply to a coil in floor heating system is important to achieve comfortable indoor air condition in the winter season. The hot water header is used to distribute the water into the coil. Experimental study has been performed using the water header that have 5 branches consisted of flow control valves and automatic shut-off valves. Each branch line connected it with X-L pipe. Experimental tests accomplished it to investigate the flow distribution characteristics of the hot water header. Experimental results show that the selection of the pump head and differential pressure are very important to save running energy of the system, and high differential pressure needs more friction loss in the case of suitable differential pressure for balancing of the header.

Design of the Current Segment Coil for Accelerating the Magnetic Materials (자성물질을 가속시키기 위한 전류 Segment 코일의 설계)

  • Chung, Byung-Tae
    • The Journal of the Korea institute of electronic communication sciences
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    • v.7 no.4
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    • pp.861-866
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    • 2012
  • The distance optimizing between coil and magnetic materials never be specified in the magnetic materials acceleration using the coil till now. We can know to be the distance which optimizes when being in the half position about the distance of intercoil by the result of the max point on the Differential calculus. Whether several top and bottom current segment coil structures were made and the steel ball in which the current segment coil structure is the magnetic materials could be accelerated in the optimizing distance or not confirmed. When the coil valley current about the mass of the steel ball was known as the experiment and it was but to be the nose consequently it applied to the magnetic materials and magnetic fluid, the optimal distance was solved between the coil and material.

Optimal Coil Configuration Design Methodology Using the Concept of Equivalent Magnetizing Current (등가자화전류를 이용한 최적코일형상 설계방법)

  • Kim, Woo-Chul;Kim, Min-Tae;Kim, Yoon-Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.1 s.256
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    • pp.43-49
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    • 2007
  • A new electric coil design methodology using the notion of topology optimization is developed. The specific design problem in consideration is to find optimal coil configuration that maximizes the Lorentz force under given magnetic field. Topology optimization is usually formulated using the finite element method, but the novel feature of this method is that no such partial differential equation solver is employed during the whole optimization process. The proposed methodology allows the determination of not only coil shape but also the number of coil turns which is not possible to determine by any existing topology optimization concept and to perform single coil strand identification algorithm. The specific applications are made in the design of two-dimensional fine-pattern focusing coils of an optical pickup actuator. In this method, the concept of equivalent magnetizing current is utilized to calculate the Lorentz force, and the optimal coil configuration is obtained without any initial layout. The method is capable of generating the location and shape of turns of coil. To confirm the effectiveness of the proposed method in optical pickup applications, design problems involving multipolar permanent magnets are considered.

A Study on measuring the Initial Permeability of Magnetic Powder considered Demagnetizing factors (반자장계수를 고려한 자성분말의 초투자율 측정에 관한 연구)

  • Jun, Hong-Bae;Heo, Jin;Kim, Chul-Han;SaGong, Geon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.05b
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    • pp.86-90
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    • 2000
  • In this study, A equipment for measuring the initial permeability of soft-ferrite powder was developed by using a differential transformer coil, and was investigated demagnetizing factors. To measure the initial permeability of magnetic ceramic powder is cumbersome since there are not any measuring equipment and method. Magnetic powder is currently used for a magnetic fluid and microwave absorber materials, and the initial permeability of the magnetic powder is very important to be evaluated a powder for some applications.

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Drawing of Impedance Plane Diagrams of Absolute Coil ECT Signals by finite Element Analysis (유한요소해석에 의한 절대코일 와전류 신호의 임피던스 평면도 작성)

  • Shin, Young-Kil;Lee, Yun-Tai;Lee, Jeong-Ho;Song, Myung-Ho
    • Journal of the Korean Society for Nondestructive Testing
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    • v.24 no.4
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    • pp.315-324
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    • 2004
  • In eddy current testing(ECT), differential probes have been frequently used since they .an reduce the number of parameters that influence ECT signals. However, differential signal is actually the difference of the two coils' impedance so that signal prediction and interpretation are not easy, On the other hand, absolute coil signal is rather straightforward to predict and analyze. Therefore, combined use of the two types of signals would increase the test reliability. In this paper, absolute coil signals from Inconel plate and tubes are predicted by the finite element analysis and efforts of lift-off, fill-factor, conductivity, operating frequency, test specimen thickness, inner diameter defects, and outer diameter defects are investigated. As a result, various impedance plane diagrams are drawn and analyzed. Significant practical knowldege about absolute signals is accumulated and similar characteristics of the two types of signal could be understood. Finally, slope angle versus defect depth calibration corves are prepared for three different frequencies.

Experimental Study of Friction Factors for Laminar, Transition, and Turbulent Flow Regimes in Helical Coil Tubes (헬리컬 코일 튜브에서의 층류, 천이, 난류 영역의 마찰계수에 대한 실험적 연구)

  • Park, Won Ki;Kim, Taehoon;Do, Kyu Hyung;Han, Yong-Shik;Choi, Byung-Il
    • Journal of the Korean Society of Safety
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    • v.33 no.1
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    • pp.7-15
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    • 2018
  • The friction factors according to the flow regimes in helical coil tubes depend on the coil diameter, the tube diameter, and the coil pitch. In previous studies, correlations for the laminar flow regime in helical coil tubes have been proposed. However, studies on the transition flow regime and the turbulent flow regime are insufficient and further researches are necessary. In this study, characteristics of the friction factors for the laminar, transition and turbulent flow regimes in helical coil tubes were experimentally investigated. The helical coil tubes used in the experiments were made of copper. The curvature ratios of the helical coil tubes, which means the ratio of helical coil diameter to inner diameter of the helical coil tube are 24.5 and 90.9. Experiments were carried out in the range of $529{\leq}Re{\leq}39,406$ to observe the flows from the laminar to the turbulent regime. The friction factors were obtained by measuring the differential pressures according to the flow rates in the helical coil tubes while varying the curvature ratios of the helical coil tubes. Experimental data show that the friction factors for the helical coil tube with 24.5 in the curvature ratio of the helical coil tube were larger than those in the straight tube in all flow regimes. As the curvature ratio of the helical coil tube increases, the friction factor in turbulent flow regime tends to be equal to that of the straight tube. In addition, it was confirmed that the transition flow regimes in the helical coil tubes were much wider than those in the straight tube, also the critical Reynolds numbers were larger than those in the straight tube. The results obtained in this experimental study can be used as basic data for studies on the water hammer phenomenon in helical coil tubes.