• Journal of Power Electronics
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• v.16 no.4
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• pp.1277-1287
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• 2016

This study proposes a novel isolated high step-up galvanic converter, which is suitable for renewable energy applications and integrates a boost converter, a coupled inductor, a charge pump capacitor cell, and an LC snubber. The proposed converter comprises an input inductor and thus features a continuous input current, which extends the life of the renewable energy chip. Furthermore, the proposed converter can achieve a high voltage gain without an extremely large duty cycle and turn ratio of the coupled inductor by using the charge pump capacitor cell. The leakage inductance energy can be recycled to the output capacitor of the boost converter via the LC snubber and then transferred to the output load. As a result, the voltage spike can be suppressed to a low voltage level. Finally, the basic operating principles and experimental results are provided to verify the effectiveness of the proposed converter.

• Proceedings of the KIEE Conference
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• 2007.04c
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• pp.62-64
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• 2007

This paper deals with design of high speed linear switched reluctance motor(LSRM). First, we derived design factor from pole arc ratio of stator and mover, and calculated time constant using inductance and resistance. Second, we decided design parameter from design factor using time constant. Finally, analyze characteristics for LSRM using finite element analysis.

• Proceedings of the KIEE Conference
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• 2007.04c
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• pp.68-70
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• 2007

The operational characteristics of superconducting fault current limiter (SFCL) using magnetic coupling of coils were investigated. This SFCL consists of a high-Tc superconducting (HTSC) element and two coils with series or parallel connection on the same iron. This SFCL has the merit that the operational current of SFCL can be increased higher than the critical current of the superconducting element by adjusting the inductance ratio between two coils. To confirm its operation, the circuit for the fault simulation was constructed. From the measured voltage and current of the SFCL, it was confirmed that the resistance of HTSC element comprising this SFCL increased more than that of HTSC element's independent operation.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.382-384
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• 2008

Hold-up time is a special requirement for the front end DC/DC converter in a server power supply. It forces the converter with the variable switching frequency to operate in a wide switching frequency range, which makes the regulation difficult and reduces the power density. In this paper a novel frequency controlled half bridge converter with the hold-up time extension circuit is proposed. During the hold-up time, the auxiliary switches are turned on, thus the resonant inductance is reduced and the voltage conversion ratio is increased. Therefore, the output capacitor of the power factor correction (PFC) circuit can be decreased, and the converter can have high power density. The proposed converter is verified by experimental results from a prototype with 700W, 400V input, and 12V output.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.271-273
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• 2000

A magnetic field generator for small animal study was designed and constructed. For calculation of magnetic fields inside the cage, a three-dimensional calculation program was made. Using this, optimum electric current ratio and position of each coil were determined. Meanwhile, inductance of the generator was calculated for design of power supply. The field measurement results of the manufactured generator showed that the difference between maximum and minimum magnetic field at the living floor was less than 2%.

• Journal of Power Electronics
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• v.18 no.2
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• pp.383-394
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• 2018

This paper presents an isolated power factor correction converter for general-purpose electric vehicle chargers with a wide output voltage range. The converter is based on an asymmetrical dual active bridge structure so that the voltage stress of switching devices can be eliminated by transferring the transformer leakage inductance to the circuit parameters. Harmonic and output controls are performed by secondary switches, and primary switches are only operated at a fixed frequency with a 50% duty ratio. A harmonic modulation technique is also adopted to obtain a near-unity power factor without input current monitoring. The feasibility of the proposed charger is verified with a 3.3 kW prototype.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.2
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• pp.149-154
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• 2008

An air-gapped current transformer(CT) has been used to reduce a remanent flux in the core, particularly in the case of auto-reclosure. However, it causes larger transient, ratio and phase errors than the iron-cored CT because of the small magnetizing inductance. This paper proposes a compensation algorithm for the secondary current of the air-gapped CT during the fault conditions including auto-reclosure as well as in the steady-state. The core flux is calculated from the measured secondary current of the CT and inserted into the hysteresis loop to estimate the exciting current. Finally, the correct current is estimated by adding the measured secondary current to the estimated exciting current. Various test results clearly indicate that the proposed compensating algorithm can improve the accuracy of the air-gapped CT significantly and reduce the required core cross-section of the air-gapped CT significantly.

• Proceedings of the KIEE Conference
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• 2008.10c
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• pp.59-61
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• 2008

This paper deals with design of Linear Switched Reluctance Motor (LSRM) considering to normal force. First, we derived design factor from pole arc ratio of stator and mover, and calculated time constant using inductance and resistance. Second, we decided design parameter from design factor using time constant, and analyze characteristics for LSRM using finite element analysis. Finally, we analyzed force characteristic according to design factor.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.3
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• pp.300-310
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• 1992

This paper deals with the problem of robust pole-assignment control for linear systems with structured uncertainty. It considers two cases whose colsed-loop characteristic equations are presented as a family of interval polynomial and polytopic polynomial family respectively. We propose a method of finding the pole-placement region in which the fixed gain controller guarantees the required damping ratio and stability margin despite parameter perturbation. Some results of Kharitonov like stability and two kinds of transformations are included. As an illustrative example, we show that the proposed method can apply effectivly to the single magnet levitation system including some uncertainties (mass, inductance etc.).

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.10
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• pp.457-464
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• 2005

Both ratio error and phase angle error in potential transformer(PT) are critically affected by used burden, connected in parallel to the secondary terminal of the PT. Thus precise measurement of burden value is very important for the evaluation of PT An automatic measurement system has been developed for the measurement of burden value and power factor of a burden. The ac voltage, current and power of the burden are measured precisely, and the burden value and power factor were calculated from these measured values. The resistance and inductance values of the tested burden are also calculated. The overall measurement uncertainties are calculated and reported with the burden value and power factor. The best measurement uncertainty for the burden measurement with the developed automatic measurement system was estimated to be 0.5 $\%$.