• Journal of the Korean Society of Industry Convergence
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• v.22 no.3
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• pp.365-371
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• 2019

Recently, the demonstration and research on the power transmission using high voltage DC such as HVDC(High Voltage DC), Smart Grid, DC transmission and distribution have been actively conducted. In order to control the power converter in high-voltage DC power transmission system, SMPS(Switching Modulation Power Supply) for power converter control using high-voltage DC input is essential. However, the demand for high-pressure SMPS is still low, so the development is not enough. In the low-output SMPS using the high-voltage input, it is difficult to achieve high efficiency due to the switching transient loss especially at light load. In this paper, we propose a new switching scheme for high power SMPS control for low output power. The proposed method can provide better efficiency increase effect in the light load region compared to the existing PWM method. To verify the feasibility of the proposed method, a 40 W SMPS for HVDC MMC(Modulation Multi-level Converter) was designed and verified by simulation.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.126-129
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• 2007

The particle formation using pyrolysis has many advantages over other particle manufacturing techniques. The particles by pyrolysis have relatively uniform size and chemical composition. Also, we can easily produce high purity particles. Thus, we studied the formation of silicon particles by pyrolysis of 50% $SiH_4$ gas diluted in Ar gas. A pyrolysis furnace was used for the thermal decomposition of $SiH_4$ gas at $800^{\circ}C$ and atmospheric pressure. The aerosol flow from furnace is separated into two ways. The one is to the Scanning Mobility Particle Sizer (SMPS) for particle size distribution measurement and the other is to the particle deposition system. The produced silicon particles are deposited on the wafer in the deposition chamber. SEM measurement was used to compare the particle size distribution results from the SMPS. Depending on the experimental conditions, particles of high concentration in the $30\sim80$ nm size range were generated.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2192-2194
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• 1999

In this study, We have accomplished a new approach to develope a cheap and compact pulsed $CO_2$ laser system. We used a fast SCR as switching device instead of a thyatron in the pulsed power supply. Using the Pulse transformer, energy in the condenser is tranferred to the secondary, electrodes of discharge tube, from the primary. An axial and water cooled type was adopted as the laser cavity. The laser performance characteristics as various parameters, such as gas pressure and pulse repetition rate, have been investigated. As a result, the maxium laser output was 12.3[W] at a pulse repetition rate of 120[pps] and a filling pressure of 12[Torr].

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.11
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• pp.730-734
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• 1999

In this study, it is the purpose to develope a cheap and compact repetitively pulsed $CO_2$ laser with pulse repetition rate range of 180 Hz. We used a SCR switched power supply as a high voltage pulsed supply, which is cheap and simple comparing to others. PIC one-chip microprocessor was used for precise control of a laser power supply on the control part. And the laser cavity was fabricated as an axial and water cooled type. The laser performance characteristics as various parameters, such as pulse repetition rate and gas pressure have been investigated. The experiment was done under the condition of total pressure of $CO_2, N_2$ and He from 4 Torr to 16 Torr and pulse repetition rate from 4 Hz to 180 Hz. As a result, the maximum average output was about 19.6W at the total pressure of 12 Torr and the pulse repetition rate of 180Hz.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.257-260
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• 2002

In this paper, the circuit of AC Choppers for $CO_2$laser Power Supply are proposed and investigated. IGBT-controlled ac voltage regulators, operating at high frequency chopping mode. Chopping-to-supply duty ratio plays an important role in terms of laser output. Laser input energy is varied by controlling the leakage transfomer used with the proposed system. This improved circuit employs a 3 electrode-type and Ring Blower. This improved circuit system has many advantages compared with the conventional SMPS such as simple design requirment, easy implementation, high reliability, low switching loss, and consequently high efficiency. As a result, the maximun output was 16W at duty-ratio of 92%, total gas mixture of $CO_2$: $N_2$: He = 1 : 9 : 15, total pressure of 15torr.

• Journal of the Korean Society of Safety
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• v.36 no.2
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• pp.10-17
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• 2021

This paper presents the robust design of each component used in the development of an induction bolt heating system for dismantling the high-temperature high-pressure casing heating bolts of turbines in power plants. The induction bolt heating system comprises seven assemblies, namely AC breaker, AC filter, inverter, transformer, work coil, cable, and CT/PT. For each of these assemblies, the various failure modes are identified by the failure mode and effects analysis (FMEA) method, and the causes and effects of these failure modes are presented. In addition, the risk priority numbers are deduced for the individual parts. To ensure robust design, the insulated-gate bipolar transistor (IGBT), switched-mode power supply (SMPS), C/T (adjusting current), capacitor, and coupling are selected. The IGBT is changed to a field-effect transistor (FET) to enhance the voltage applied to the induction heating system, and a dual-safety device is added to the SMPS. For C/T (adjusting current), the turns ratio is adjusted to ensure an appropriate amount of induced current. The capacitor is replaced by a product with heat resistance and durability; further, coupling with a water-resistant structure is improved such that the connecting parts are not easily destroyed. The ground connection is chosen for management priority.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1697-1699
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• 2001

In this paper, the circuit of AC Choppers for $CO_2$ laser power supply are proposed and investigated. IGBT-controlled ac voltage regulators, operating at high frequency chopping mode. Chopping-to-supply duty ratio plays an important role in terms of laser output. Laser input energy is varied by controlling the leakage transformer used with the proposed system. This improved circuit employs a 3 electrode - type and Ring Blower. This improved circuit system has many advantages compared with the conventional SMPS such as simple design requirement, easy implementation, high reliability, low switching loss, and consequently high efficiency. As a result, the maximun output was 16W at duty-ratio of 92%, total gas mixture of $CO_2$ : $N_2$ : He = 1 : 9 : 15, total pressure of 15torr.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.3
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• pp.65-72
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• 2011

In this study, the numbers, sizes of particles from a single cylinder direct injection spark-ignition (DISI) engine fuelled with gasoline and LPG are examined over a wide range of engine operating conditions. Tests are conducted with various engine loads (2~10bar of IMEP) and fuel injection pressures (60, 90, and 120 bar) at the engine speed of 1,500 rpm. Particles are sampled directly from the exhaust pipe using rotating disk thermodiluter. The size distributions are measured using a scanning mobility particle sizer (SMPS) and the particle number concentrations are measured using a condensation particle counter (CPC). The results show that maximum brake torque (MBT) timing for LPG fuel is less sensitive to engine load and its combustion stability is also better than that for gasoline fuel. The total particle number concentration for LPG was lower by a factor of 100 compared to the results of gasoline emission due to the good vaporization characteristic of LPG. Test result presents that LPG for direct injection spark ignition engine help the particle emission level to reduce.