• Journal of Power Electronics
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• v.18 no.3
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• pp.778-788
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• 2018

Magnetic resonance wireless power transfer (WPT) in the marine environment can be utilized in many applications. However, energy loss in seawater through eddy loss (EL) is another consideration other than WPT in air. Therefore, the effect of system parameters on electric field intensity (EFI) needs to be measured and ELs calculated to optimize such a system. In this paper, the usually complicated analytical expression of EFI is simplified to the product of frequency, current, coil turns, and a coefficient to analyze the eddy current loss (ECL). Moreover, as the calculation of ECL through volume integral is time-consuming, the equivalent eddy loss impedance (EELI) is proposed to help designers determine the optimum parameters quickly. Then, a power distribution model in seawater is conceived based on the introduction of EELI. An optimization flow chart is also proposed according to this power distribution model, from which a prototype system is developed which can deliver 100 W at 90% efficiency with a gap of 30 mm and a frequency of 107.1 kHz.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.66-75
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• 1993

This paper proposes a monitoring method for nondestructive and in-process measurement of the case depth in LASER surface heat treatment process. The method is essentially an eddy-current method, and measures sensing coil's electrical impedance which varies with the changes of the material microstructure due to hardening. To investigate te validity of the proposed method a series of experiments were performed for various hardning depths. The results show that the relationship between the eddy- current sensor output and the changes in case depth is almost linear. This indicates that the eddy-current measuring method can be used as one of the possible monitoring method for mesauring the hardened depth in LASER heat treatment processes.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1045-1047
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• 2003

The development of linear Eddy-Current brake systems has gradually gone beyond the adhesion limit in high-speed vehicles. In particular, the practicality of using permanent magnet in Eddy-Current brake systems is obviously recent, due to the manifold improvement in magnet materials and technology. On the basis of analytical two-dimensional field solution, this paper deals with flux density and force calculation about the linear Eddy-Current brake systems: DC excited electromagnet, Halbach magnetized and vertical magnetized permanent magnet.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.6
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• pp.406-418
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• 2015

The present modified FUNWAVE-TVD model, which is a modification to its previous version 2.1, is applied to solitary wave propagation and is tested against the experiments of Vincent and Briggs(1989) and Luth et al.(1994). The eddy viscosity breaking scheme is used for comparison with the existing study in the case of breaking experiment. The symmetry of wave-induced current is maintained when the modified model is employed to Vincent and Briggs(1989) breaking experiment, but the symmetry of wave-induced current in previous model is not maintained. A better agreement with the breaking experimental data is obtained in the modified model using eddy viscosity breaking scheme than the shock capturing breaking scheme using nonlinear shallow water equation. For comparison with the schemes in the model, the fourth order MUSCL-TVD scheme by Erduran et al.(2005) and the third order MUSCL-TVD scheme using minmod limiter is applied, and the numerical solutions of solitary wave are compared.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.264-268
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• 2005

Most of the train brakes depends on friction between wheels and tracks. This requires braking force reduced in order not to cause wheel slides since the friction decreases as the train speed increases and consequently results in extension of braking distance. The braking system called 'Linear eddy current brake' or simply' Eddy current brake' is a braking system for making a brake independent from friction, which consists in creating electromagnet by coiling around shoes attached. to bogies; having the shoes above the tracks approached to the tracks upon acknowledgement of a braking command; and authorizing braking force that is irrelevant to friction through magnetic repulsion between electromagnet attached to the tracks and train set by the use of the electromagnet's magnet field characteristics. An electromagnetic attraction braking system that consists in pressing pole shoes attached to bogies against the tracks by using electromagnet's attraction force is called 'Electromagnetic track brake' or simply 'Track brake'. This paper has been prepared in purpose of studying technological tendencies of the eddy current brake and the track brake so that it can be utilized as fundamental data for commissioning Korean high-speed trains with the eddy current brake hereafter.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.115-116
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• 2009

• Journal of Power System Engineering
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• v.14 no.2
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• pp.60-64
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• 2010

This paper introduces reliability improvement and time saving in eddy current inspection by signal characteristic optimization of multi-coil eddy current array probe. In the past, Multi-coil array probe and single probe were used for the gas turbine rotor surface inspection & defect evaluation. The multi-coil array probe was used for the broad area inspection. But the signal deviations among multi-coil array probe are maximum 28% in commercial probe. This differences were considered to impedance differences among coils, so it is very difficult to evaluate exact defect size. The signal deviations among multi-coil array probe are maximum 28% in commercial probe. So, single coil inspection was used for exact defect sizing. The purpose of this study is to improve signal deviations of multi-coil array probe. The introduced new technology can improves this deviation by adjusting input voltage in each coil. At first, apply same voltage in each coil and collect signal amplitude of each coil. And calculate new input voltage based on signal amplitude of each coil. If the signal amplitude deviation is within 5% among multi-coil array probe, the signal amplitude of multi-coil array probe is reliable. The proposed technology gives 2% signal deviation among multi-coil array probe. The proposed new technology gives reliability improvement and inspection time saving in eddy current inspection.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.3
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• pp.294-301
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• 2015

Oil filters for vehicular parts are used under high and low temperatures as the engine is cooled, and defects can be generated with repeated changes in the operating environment and with changes in the shape, such as very high internal losses for the bolts. Visually checking for defects inside a bolt is impossible. Nondestructive evaluation methods such as eddy current testing (ECT) are recommended as a more effective way to examine inside a bolt and detect surface defects in a short amount of time. In this study, the fit bobbin coil eddy current probe was applied to checking the bolts. The bolt parameters were calculated by using a COMSOL analysis program to obtain parameters for professional interior design and fault diagnosis.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.655-656
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• 2008

This research presents a topology optimization to minimize eddy current loss maintaining mechanical robustness of structure part in electrical machines A design sensitivity equation for the topology optimization is derived by employing the discrete system equations combined with the adjoint variable method. As a numerical example, frame design of a C-core actuator is performed by the proposed method.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.125-127
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• 2003

Brake forces due to eddy-currents induced by the relative motion of a conductor and a magnetic devices: motors, brakes and magnetically levitated vehicles. In particular, the practicality of using permanent magnet in eddy-current brakes system is obviously recent, due to the manifold improvement in magnet materials and technology. For such a system we give analytical formulas considering eddy-current distribution as variables: flux density for each region and forces.