• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2000.11a
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• pp.251-256
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• 2000

The assessment of the condition of a transformer winding which is suspected of having suffered short circuit damage can be difficult. Conventional test such as winding resistance, magnetisation current or insulation resistance will only detect damage if a permanent electrical fault exists. Visual inspection of windings necessitates the removal of oil and in many cases only a very small proportion of the winding can be seen. We describe the characteristics. As the front rise time of recurrent-surge generator pulse less than 1000ns and the peak value of pulse is about 500V, we have the good results of detecting winding deformation in the LVI test of transformers.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.841-846
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• 1998

The superconducting permanent current switch (PCS) is an important component to build MRI system. This switch uses a thermal and / or magnetic super-to-normal phase transition of the superconductor. Unfortunately, in the past it was not designed for using in line frequency. We made some superconducting power electronics devices operating up to 100 Hz [1]. The results of development and preliminary studying of the hear controlled S-PED up to line frequency are presented.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.289-292
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• 2002

A sensorless control of a PM synchronous motor under the parameter variation is presented. The rotor position is estimated by using the d-axis and q-axis current errors between the real system and motor model of the estimator. The stator resistance is measured at low speeds when the motor changes its rotating direction. The gains in the position estimator are also adapted according to the motor speeds.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.119-122
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• 2003

This paper describes the sensorless technique for the surface-mounted permanent-magent synchronous motor(SPMSM or PMSM) drive based on magnetic saliency. The control technique is a sensorless control algorithm that injects the high frequency voltage to the stator terminal in order to estimate the rotor position and speed. The rotor position and speed for sensorless vector control is achieved by appropriate signal processing to extract the position information from the stator current in the low speed range including zero speed. Proposed sensorless algorithm using the double-band hysteresis controller and initial rotor position detection exhibits excellent reference tracking and increased robustness. Experimental results are presented to verify the feasibility of the proposed control schemes.

• Journal of Power Electronics
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• v.9 no.2
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• pp.188-197
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• 2009

This paper presents an adaptive flux observer to estimate stator flux linkage and stator inductances of an interior permanent-magnet synchronous machine considering magnetic saturation. The concept of static and dynamic inductances due to saturation is introduced in the machine model to describe the relationship between current and flux linkage and the relationship between their time derivatives. A flux observer designed in the stationary reference frame with constant inductance is analyzed in the rotor reference frame by a frequency-response characteristic. An adaptive algorithm for an on-line inductance estimation is proposed and a Lyapunov-based analysis is given to discuss its stability. The dynamic inductances are estimated by using Taylor approximation based on the static inductances estimated by the adaptive method. The simulation and experimental results show the feasibility and performance of the proposed technique.

• KSBB Journal
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• v.23 no.1
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• pp.8-17
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• 2008

There are many different approaches to healing of acute and chronic ulcer and large skin defect, such as burn. Currently available wound covers fall into two categories. Permanent covering, such as autografts, and temporary ones, such as allograft including de-epidermized cadaver skin, bioartificial skin, xenografts, and synthetic dressings. Autologous skin grafting in the form of split- or full-thickness skin is still the good standard. Following on from developments in the 1980s involving the use of cultured keratinocyte grafts in wound healing, the last decade has been great progress in the fabrication of composite bioartificial skin grafts. However, two bottleneck on producing cultured bioartificial skin, whether of the simple epithelial cell sheet type, or the more complex composite type, continue to be the generation of sufficient keratinocytes cheaply and quickly and develop biocompatible dermal scaffolds. This article covers the development, clinical application, and current research directions associated with bioartificial skin.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.11
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• pp.1519-1525
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• 2014

This paper presents the shape design for reducing cogging torque and characteristic analysis in Brushless DC (BLDC) motor. In this BLDC motor, ${\Delta}$(delta)-winding is applied, and in order to obtain the $60^{\circ}$ trapezoidal phase back-EMF waveform, permanent magnet shape design is carried out. And then, a method on specifying design parameters to effectively reduce cogging torque is developed. back-EMF, input voltage and input current which are analyzed by the Finite Element Method (FEM) are validated by experimental results. Also, efficiency calculations based on analysis and experimental results are performed and analyzed.

• Journal of Power Electronics
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• v.13 no.4
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• pp.552-557
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• 2013

This paper proposed an analytical model for the distributed magnetic field analysis of interior permanent magnet-type blush-less direct current motors under the stator-turn fault condition using the winding function theory. Stator-turn faults cause significant changes in electric and magnetic characteristic. Therefore, many studies on stator-turn faults have been performed by simulation of the finite element method because of its non-linear characteristic. However, this is difficult to apply to on-line fault detection systems because the processing time of the finite element method is very long. Fault-tolerant control systems require diagnostic methods that have simple processing systems and can produce accurate information. Thus analytical modeling of a stator-turn fault has been performed using the winding function theory, and the distributed magnetic characteristics have been analyzed under the fault condition. The proposed analytical model was verified using the finite element method.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1994-1996
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• 2002

This paper reports a novel high-speed fluid injection system employing a simple magnetic micoractuator. This magnetic microacutator consists of current carrying copper beams and permanent magnet under the beams. There were many efforts to magnetic microactuator realization using conducting coils [1-2]. Even though many of magnetic microactuators were successfully fabricated and tested, it is true that most them suffer complex fabrication processes and thus higher production costs than electrostatic counterparts. In this research, efforts were concentrated on the microactuator realization that has simple structure, low production cost, and mass production possibility.

• Progress in Superconductivity and Cryogenics
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• v.7 no.2
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• pp.44-46
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• 2005

A SMES can be a perfect alternative energy storage device to the chemical batteries which are needed by most of the renewable energy supply systems. The chemical battery storage system is so expensive to maintain and causes another environmental problem because they are not recyclable. But, SMES has semi-permanent lifetime and no environmental problems cause it only need coolants which is non flammable, clean and recyclable gas. In order to verify the feasibility of a SMES for the renewable electrical power supply system, electrical characteristics of a test SMES coil with the photovoltaic power system were analyzed in this paper. Simulation results show that we can charge 40 amps of current in test SMES coil using solar power system. The experimental verification will be performed just after development of the peak power tracking system for the solar system.