• Journal of Power Electronics
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• v.4 no.1
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• pp.12-17
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• 2004

In this paper, a practical implementation to reduce leakage flux of a high-frequency inverter based non-contact type power transformer composed of EE-shape ferrite cores is presented for key technology of the next generation medical use X-ray CT scanner system. Design consideration for the unique structure of the non-contact power transformer with 900mm in diameter is also introduced. The complete non-contact transformer is actually arranged by several blocks of the magnetic circuit assembled by using 10 small EE shape cores with 120mm in length. It is experimentally and analytically discussed from a reduced leakage flux viewpoint related to its inductively coupling coefficient. A practical method to lower the leakage flux is described based on effective Copper-Sheet- Treatment placed on EE shape ferrite cores of magnetic circuit.

• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.539-545
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• 2000

This paper describes the design method of the magnetic system to maximize the magnetic flux leakage (MFL) in non-destructive testing (NDT) system. The defect signals in MFL type NDT system mainly depends on the change of the magnetic leakage flux in the region of defect. The characteristics of the B-H curves are analyzed and the design method to define the operating point in B-H curves for the maximum leakage is performed. The computed MFL signal by nonlinear finite element method is verified by measurement using Hall sensors mounted on the 6 legs PIG in the 8 inches test tube with defects. The rhombic defects could be successfully composed from the defect signals.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.2
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• pp.99-105
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• 2011

The magnetic circuit analysis excluding flux loss and fringing effect often gives a result with unignorable error, when compared with real system. But, it is not easy to make a complete magnetic circuit model with the loss effects. This paper introduces a relatively simple method to build the model including the flux loss and fringing effect, in which the paths of leaked flux are simplified in terms of circular arcs and straight lines. After modification of the model, the error of about 36 % in maximum between the magnetic circuit analysis and FEM analysis is reduced to about 7 %.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.245-254
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• 2009

Efficiency of landfill liners system is usually evaluated based on leakage rate and mass flux. In this study, composite liner systems including the GCL(geosynthetic clay liner) composite liner, the Subtitle D liner, the Wisconsin NR500 liner, and the recently utilized double composite liner, which is a combination of the GCL composite liner and Subtitle D-type liner, have been examined. The leakage rate through circular and long defects in the geomembrane (GM) of the liner system was analyzed with the aids of analytical and numerical methods. For the mass flux criterion, contaminant transport through defects in the GM of landfill liners can be evaluated based on the calculated leakage rates. The diffusion rate of volatile organic compounds through intact landfill liners was evaluated by performing a one-dimensional numerical model. Cadmium and toluene were adoptted in the analyses as typical inorganic and organic substances, respectively, which will be chemical species encountered during landfill operation. The performance-based evaluation indicates that the double composite liner systems are superior to the other types of liner.

• Journal of Magnetics
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• v.22 no.1
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• pp.34-42
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• 2017

Material defects in the Steam Generator Tubes (SGT) of sodium cooled fast breeder reactor (PFBR) can lead to leakage of water into sodium. The water and sodium reaction will lead to major accidents. Therefore, the examination of steam generator tubes for the early detection of defects is an important requirement for safety and economic considerations. In this work, the Magnetic Flux Leakage (MFL) based Non Destructive Testing (NDT) technique is used to perform the defect detection process. The rectangular notch defects on the outer surface of steam generator tubes are modeled using COMSOL multiphysics 4.3a software. The obtained MFL images are de-noised to improve the integrity of flaw related information. Grey Level Co-occurrence Matrix (GLCM) features are extracted from MFL images and taken as input parameter to train the neural network. A comparative study on characterization have been carried out using feed-forward back propagation (FFBP) and cascade-forward back propagation (CFBP) algorithms. The results of both algorithms are evaluated with Mean Square Error (MSE) as a prediction performance measure. The average percentage error for length, depth and width are also computed. The result shows that the feed-forward back propagation network model performs better in characterizing the defects.

• Nuclear Engineering and Technology
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• v.49 no.7
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• pp.1379-1387
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• 2017

This paper presents a comparison of homogenization techniques implemented in the APOLLO3 platform for transport core calculations: standard scalar flux weighting and new flux-moment homogenization, in different combinations with (or without) leakage models. Besides the historical B1-homogeneous model, a new B-heterogeneous one has indeed been implemented recently in the two/three-dimensional-transport solver using the method of characteristics. First analyses have been performed on a very simple Sodium Fast Reactor core with a regular hexagonal lattice. They show that using the heterogeneous leakage model in association with flux-moment homogenization strongly improves the prediction of $k_{eff}$ and void reactivity effects. These good results are confirmed when the application is done to the fissile assemblies of the more complex CFV (Low Void Effect) core of the ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) project of sodium-cooled fast breeder reactor (Generation IV).

• Smart Structures and Systems
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• v.22 no.2
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• pp.239-247
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• 2018

A magnetic flux leakage (MFL) method was applied to detect and quantify defects in a steel bar. A multi-channel MFL sensor head was fabricated using Hall sensors and magnetization yokes with permanent magnets. The MFL sensor head scanned a damaged specimen with five levels of defects to measure the magnetic flux density. A series of signal processing procedures, including an enveloping process based on the Hilbert transform, was performed to clarify the flux leakage signal. The objective damage detection of the enveloped signals was then analyzed by comparing them to a threshold value. To quantitatively analyze the MFL signal according to the damage level, five kinds of damage indices based on the relationship between the enveloped MFL signal and the threshold value were applied. Using the proposed damage indices and the general damage index for the MFL method, the detected MFL signals were quantified and analyzed relative to the magnitude of the damage increase.

• Journal of Magnetics
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• v.15 no.4
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• pp.199-203
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• 2010

This paper discusses the effectiveness of high magnetization saturation in ILI (In-Line Inspection) using an MFL (Magnetic Flux Leakage) tool, and introduces a practical method for improving the magnetization level together with the piggability. Thin steel plates, replacing the conventional wire brushes were used as conductors to transfer the magnetic flux to the pipe wall. The newly designed MFL tool was compared with the conventional version by means of FEM (Finite Element Method) analysis and full-scale experiments. In the results, the newly developed magnetization system obtained a stronger MFL signal amplitude, specially 2.7 times stronger, than that obtained by the conventional magnetization system for the same defect dimensions.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.29-31
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• 2005

The effective flux of X-Y linear motor is calculated with analytical method according to the arrangement of permanent magnet. In order to reduce leakage flux due to increased effective flux, the distance of the permanent magnet is adjusted. When the distance is 2[mm] between two magnets, the leakage flux is greatly reduced, and it is expected that if the segment of permanent magnet magnetized to x and y direction is added, the motor performance will be enhanced.

• Journal of Electrical Engineering and Technology
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• v.11 no.5
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• pp.1311-1315
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• 2016