• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.90-92
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• 2002

This paper presents an improved C-Dump converter system for switched reluctance motors(SRM). The proposed C-Dump converter derived from the conventional converter for SRM. The proposed converter could overcome the limitation of the conventional C-Dump converter, and could reduce the whole cost of the SRM system since the voltage stress of the dump switch $T_d$ is reduced to $V_{dc}$ when compared with $2V_{dc}$ for the conventional C-Dump converter. The attractive features of the proposed converters are; high-efficient and low-cost, elimination of dump inductor, simple control strategy, smaller size arid light weight. The proposed converter is able to be fast magnetization by $2V_{dc}$, which is sum of the input voltage and charging voltage of the dump capacitor. Also, this topology has many advantages such as freewheeling of phase winding without complex control, reduction of current ripple, reduction of torque ripple, and reduction of switching frequency. Simulation demonstrates the good performance of the converter.

• Journal of the Korean Society of Radiology
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• v.12 no.3
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• pp.373-379
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• 2018

The purpose of this study was to investigate quantitative data on the difference in breast entrance surface dose with changes in focus-film distance, patient posture (anteroposterior-posteroanterior), thoracic wall thickness, rib bone thickness, lung tissue thickness, tube voltage, and high-voltage rectification method in Whole Spine Scanography, which is necessary for the treatment of scoliosis patients. Given a tube voltage of 90 kVp, kerma of 0.1 mGy, focus-film distance of 260 cm, tube voltage ripple rate of 0, filter thickness of 3.5 mm, and thickness of patient's thoracic wall of 120 mm as an X-ray exposure condition, from the simulation results using the Simulation of X-ray Spectra program to confirm the reduction effect of breast entrance surface dose according to the patient's posture (AP and PA), there was a dose reduction effect in aluminum filter thickness of 2.6 times at 3.5 mm, 25.7 times the thoracic wall thickness at 120 mm, 1.43 times higher tube voltage, and 0 to 1.14 times the tube voltage ripple rate. The total dose reduction effect was about 109 times. In order to confirm the dose reduction effect of RANDO phantom posture (AP and PA), from the results of the measurements taken under the conditions that the focus-film distance was 260 cm, the tube voltage was 90 kVp, the tube current was 270 mA, the exposure time was 0.31 sec, and the tube voltage ripple rate of X-ray generators was 0, the entrance surface dose reduction effect of the breast in the PA position was found to be 20.56 times lower than that of the AP position.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.1
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• pp.33-39
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• 2022

A multi-phase brushless direct current (BLDC) motor is widely used in large-capacity electric propulsion systems such as submarines and electric ships. In particular, in the field of military submarines, the polyphaser motor must suppress torque ripple in various failure situations to reduce noise and ensure stable operation for a long time. In this paper, we propose a polyphaser current control method that can improve efficiency and reduce torque ripple by minimizing the increase in stator winding loss at maximum output torque by controlling the phase angle and amplitude of the steady-state current during open circuit failure of the stator winding. The proposed control method controls the magnitude and phase angle of the healthy phase current, excluding the faulty phase, to compensate for the torque ripple that occurs in the case of a phase open failure of the motor. The magnitude and phase angle of the controlled steady-state current are calculated for each phase so that copper loss increase is minimized. The proposed control method was verified using hardware-in-the-loop simulation (HILS) of a 12-phase BLDC motor. HILS verification confirmed that the increase in the loss of the stator winding and the magnitude of the torque ripple decreased compared with the open phase fault of the motor.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.307-310
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• 2002

A design for the input filter and the output filter of a single-phase UPS system is proposed. And also, this paper describes a reduction of the DC voltage ripple of a single-phase UPS. The input power of proposed UPS fluctuates with twice frequency of the utility source, which causes DC voltage fluctuation. The reduction of the DC voltage fluctuation requires a large DC link capacitor. The proposed method uses a LC series resonant filter paralleled with a conventional smoothing capacitor. The effectiveness of the proposed method was confirmed by simulation results.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1999.11a
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• pp.162-167
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• 1999

In Auxiliary block of High speed train Power factor correction and Harmonics reduction is very important issue for efficient energy transport. The GTO-equipped PWM converter is used for traction untill resently. but the rising power capability of IGBTs resently allows to build IGBT-equipped PWM converter with a considerably increases switching frequency. In this paper presents switching pattern, control method, operation mode and tuned filter to reduce dc link voltage ripple for paralleled converter.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.491-499
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• 2019

Recently, there has been increasing demand for power quality in power supply devices. The IEC 61000-3-2 standard requires that the AC / DC power supply for lighting meet the specifications for the power factor (PF) and total waveform distortion (THD). In addition, advanced countries in Europe are regulating the ripple rate as 15 ~ 30% for the flicker phenomenon caused by the change in the amount of foot energy due to the change in current of the output terminal. Therefore, domestic standards and regulations are being updated. This study adopted the Flyback converter to satisfy the PFC standard, and has the circuit first and second insulation function. To reduce the low frequency ripple of the LED current, Flyback, Coupled Inductor, LC parallel resonance filter, LLC resonance filter, and Cuk were simulated by PSIM to mimic each LED driving circuit. A coupled LC resonant circuit with a coupled inductor on the primary side and LC resonance on the secondary side was also proposed for output side ripple reduction.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.11
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• pp.8-12
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• 2008

For the reduction of fabrication cost and process time of AC plasma display panel (PDP), indium tin oxide (ITO) layer was patterned as bus electrode using Nd:$YVO_4$ laser. In comparison with the chemically wet etched ITO patterns, laser ablated ITO patterns showed the formation of shoulders and ripple-like structures at the edge of the ITO lines. For the reduction of shoulders and ripple-like structures, pulse repetition rate and scan velocity of laser was changed. In addition, we analyzed a discharge characteristic of PDP test panel to observe how the shoulders and ripple-like structures influence on the PDP. Based on experimental results, the pattern etched at the 500 mm/s and 40 kHz was better than any other condition. From this experiment we could see the possibility of the laser direct patterning for the application to the patterning of ITO in AC-PDP.

• Journal of Power Electronics
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• v.17 no.2
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• pp.368-379
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• 2017

In this paper, a direct torque control algorithm with novel duty cycle-based modulation is proposed for permanent magnet synchronous motor drives fed by neutral-point clamped three-level inverters. Compared with the standard DTC, the proposed algorithm can suppress steady-state torque ripples as well as ensure neutral-point potential balance and smooth vector switching. A unified torque/flux evaluation table with multiple voltage vectors and precise control levels is established and used in this method. This table can be used to evaluate the effects of duty-cycle vectors on torque and flux directly, and the elements of the table are independent of the motor parameters. Consequently, a high number of appropriate voltage vectors and their corresponding duty cycles can be selected as candidate vectors to reduce torque ripples by looking up the table. Furthermore, small vectors are incorporated into the table to ensure the neutral-point potential balance with the numerous candidate vectors. The feasibility and effectiveness of the proposed algorithm are verified by both simulations and experiments.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.3
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• pp.164-172
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• 2004

This paper presents the comparison results of some kinds of control method in circumstance of eccentric load. The plant to be controlled is a computed tomography(CT) driven by a permanent magnet synchronous motor. In a CT system, many units are attached on the rotationally part of a gantry such as x-ray tube, detector, heat exchanger, and data acquisition unit etc. Therefore keeping many components to balance which have different weight is not easy; this is inescapable problem in the all CT systems. To solve this problem against eccentric load, some kinds of control method have been compared and analysed by using protype CT. From the experimental results it is vilified that the CT drive system with model reference control method indicates higher speed regulation ability regardless of variable eccentric weight and uncertain position, and also in the limit condition of constant eccentric weight and fixed position, the compensation method with sinusoidal form is a strong candidate in view of speed ripple reduction.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.11
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• pp.1625-1633
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• 2012

In the lighting industry, a Lighting Emitting Diode (LED) is increasingly used because of many advantages and a eco-friendly product comparing with the conventional lighting. However, the LED lighting has to include various AC/DC converters because the direct current is used for the LED lighting. Among a lot of power converters, the flyback converter is widely used for the LED lighting and includes some electrolytic capacitors for the voltage regulation. But the electrolytic capacitor has shorter lifetime than the LED element. It makes the expected life-time of the converter having the electrolytic capacitor shorter than the LED element. This paper proposes the single-stage PFC flyback converter without electrolytic capacitors. To verify the performance of the proposed converter, simulated and experimental works were carried out.