• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.923-925
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• 2002

The existing contactless inductive coupler has many problems because of its large volume and high level of exciting current, so a new contactless inductive coupler is being required under the circumstances and the load requirement. For a contactless inductive coupler in the manufacturing equipment of semiconductor, the coupler's efficiency is low because of its small magnetic inductance and large leakage inductance. Moreover, the high frequency switching to increase energy density per unit volume increases the iron loss and the eddy current loss, so it must be considered deeply when selecting core materials. Therefore, this paper presents core materials and shape to improve the performance of the contactless inductive coupler according to the coil positions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.195-198
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• 1999

For the thixoforming process beside an existing solidus-liquidus interval, the reheating conditions to obtain the globular microstructure are very important. It relies on the control of globular microstructure of semi-solid alloys that contain non-dendritic particles. To obtain the globular microstructure in cross section of billet, the optimal design of the induction coil is necessary. Therefore, in this paper the optimal coil design to minimize electromagnetic end effect will be proposed. The results of coil design were also applied to the reheating process to obtain a fine globular microstructure. Finally, reheating data base of aluminum alloys for thixoforming and FEM model for induction heating based on the optimal coil design have been proposed.

• Progress in Medical Physics
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• v.19 no.1
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• pp.42-48
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• 2008

Bio-implantable devices such as heart pacers, gastric pacers and drug-delivery systems require power for carrying out their intended functions. These devices are usually powered through a battery implanted with the system or are wired to an external power source. This paper describes an inductive power transmission link, which was developed for an implantable stimulator for direct stimulation of denervated muscles. The carrier frequency is around 1MHz, the transmitter coil has a diameter of 46mm, and the implant coil is 46mm. Data transmission to the implant with amplitude shift keying (ASK) and back to the transmitter with passive telemetry can be added without major design changes. We chose the range of coil spacing (2 to 30mm) to care for lateral misalignment, as it occurs in practical use. If the transmitter coil has a well defined and reliable position in respect to the implant, a smaller working range might be sufficient. Under these conditions the link can be operated in fixed frequency mode, and reaches even higher efficiencies of up to 37%. The link transmits a current of 50 mA over a distance range of 2-15 mm with an efficiency of more than 20% in tracking frequency. The efficiency of the link was optimized with different approaches. A class E transmitter was used to minimize losses of the power stage. The geometry and material of the transmitter coil was optimized for maximum coupling. Phase lock techniques were used to achieve frequency tracking, keeping the transmitter optimally tuned at different coupling conditions caused by coil distance variations.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1957-1959
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• 2004

In this paper, maxwell 3D finite element analysis program was used to obtain electromagnetic properties associated with the coil and nearby structures. The electromagnetic emitting properties were presented by 3D simulation software operated at 2.56[MHz] and some specific conditions.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.943-944
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• 2007

In this paper, the development and the test of 13.2kV/630A high-Tc superconducting fault current limiting coil are described. The fault current limiting coil made of Coated Conductor (CC) was fabricated with bifilar winding method for non-inductive characteristics and tested in the distribution power system level in Dec. 2006. In order to determine the length of the superconducting coil, applied voltage per unit length(V/m) was studied analytically and it was verified through experiments. For the volume minimization, the coil was designed with concentrical arrangement method. The short-circuit test was performed with the prospective fault current of asymmetrical 10kA whose maximum fault current was $30kA_{peak}$. In the test, the voltage drop and the current of the coil were measured and the resistance of the coil was obtained. Also, the temperature rise of the coil was calculated with the relationship between the resistance and the temperature of CC. In this paper, the experimental results are analyzed and compared with the simulation.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.3
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• pp.54-60
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• 2001

A newly designed inductive micro displacement detecting system is presented. The proposed inductive system consists of driving coils, position-detecting coils, cores, and closed-loop formed magnetic blocks. The cores and magnetic blocks are made of Mn-Zn ferrite. When AC sine wave is applied to the driving coils, the time derivative flux is generated within the system, and then induced voltages arise in the position-detecting coils according to the core\`s position. Putting the cores to be moved proportionally to the input displacement, the induced voltage is proportional to input displacement. The parameters that affect the system characteristics are turn ratio, air-gap size, excitation frequency, overlap area, load resistance, capacitance effect, and so forth. Based on the experimental results, the system parameters are selected in such a way as to have high sensitivity ad stable responses. The sensitivity of the proposed inductive displacement-detecting system is greater than 2800mV.V-1mm-1 and the linearity error is below $\pm$0.10% in the range of $\pm$200㎛.

• Progress in Superconductivity and Cryogenics
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• v.13 no.1
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• pp.17-21
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• 2011

A hybrid superconducting fault current limiter (SFCL) with fast switch had been previously suggested by our research group. To make a hybrid SFCL, different superconducting wires were wound two pancake coils so that two pancake coils had asymmetric configuration. The impedance of the asymmetric non-inductive coils are zero with applied normal current. However during the fault. currents were distributed unequally into the two pancake coils because each superconducting wires have different electrical characteristics. This unequal distribution of current causes effective magnetic flux which generate repulsive force. Fast switch was thus opened by the force applied to the aluminum plate which consists of SFCL. In this paper, the AC loss characteristics of the asymmetric non-inductive coils with combinations of superconducting wires were studied and calculated by related experiments and finite element method (FEM) simulation. From these results, we suggested the appropriate combination of two superconducting wires to be used for the asymmetric non-inductive coils.

• Progress in Superconductivity and Cryogenics
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• v.18 no.1
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• pp.55-58
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• 2016

Quench Detection System (QDS) is essential to guarantee the stable operation of the Korea Superconducting Tokamak Advanced Research (KSTAR) Poloidal Field (PF) magnet system because the stored energy in the magnet system is very large. For the fast response, voltage-based QDS has been used. Co-wound voltage sensors and balanced bridge circuits were applied to eliminate the inductive voltages generated during the plasma operation. However, as the inductive voltages are hundreds times higher than the quench detection voltage during the pulse-current operation, Central Difference Averaging (CDA) and MIK, where I and K stand for mutual coupling indexes of different circuits, which is an active cancellation of mutually generated voltages have been suggested and studied. In this paper, the CDA and MIK technique were applied to the KSTAR magnet for PF magnet quench detection. The calculated inductive voltages from the MIK and measured voltages from the CDA circuits were compared to eliminate the inductive voltages at result signals.

• Journal of Biomedical Engineering Research
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• v.29 no.4
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• pp.267-271
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• 2008

The RF shimming technique has been used to improve the transmit RF field homogeneity in highfield MRI. In the RF shimming technique, the amplitude and phase of the driving currents in each coil element are optimized to get homogenous flip angle or uniform image intensity. The inductive and capacitive coupling between the coil elements may degrade the RF field homogeneity if not taken into account in the optimization procedure. In this paper, we have analyzed the coupling effects on the RF shimming using a sixteen-element TEM RF coil model operating at 300 MHz. We have found that the coupling effects on the RF shimming can be reduced by putting high dielectric material between the active rung and the shield.

• Progress in Superconductivity and Cryogenics
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• v.2 no.1
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• pp.24-30
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• 2000

This paper present the characteristics of the internal induced voltage and arc phenomena in liquid helium at the energy transfer from a superconducting magnet to a load resistor. Especially generation mechanism of the oscillated wave from of the coil terminal voltage is analyzed by considering circuit constant of the superconducting magnet, load condition and arc resistance of the mechanical opening switch. The wavefront and peak portion of the voltage are strongly influenced by arc discharge triggered by the switch separation in liquid helium. Abrupt arc extinction leads to voltage oscillation with an enormous peak. It is suggested that the superconducting magnet should be designed to ensure the internal surge when arc is possibly formed by switch opening or coil short circuit between turns or layers. Finally, a suppression method of the oscillating surge is proposed based on the load condition.