• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.106-111
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• 2000

EP(Electrostatic Precipitator) has been used to keep the natural environment from fly-ash in the industrial fields and operated in intermittent PEC(Pulse Energized Control) mode to improve dust-collecting efficiency. Intermittent PEC mode induces low-frequency harmonic currents into power system, therefore EP transformer vibrates. This continuous transformer vibration developes transformer abnormal audio-noise and if it is too much or operates in the region of natural frequency, transformer will be damaged in the end. EP interruption caused by transformer damage results in power generation stopped, power quality down and economic loss. Therefore, this paper explains harmonic currents and transformer vibration-core vibration, winding vibration, and proposes the measures of suppressing the vibration with EP operated in intermittent PEC mode. And this results is proposed to be used for future EP transformer design or EP control method to operate EP-concerned equipment safely keeping from system faults caused by transformer vibration.

• Journal of the Korean Society for Railway
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• v.14 no.5
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• pp.411-415
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• 2011

DC/DC switching power converters are commonly used to generate a regulated DC output voltages with high efficiencies from different DC input sources. The voltage mode DC/DC converter utilizes MOSFET (metal-oxide semiconductor field effect transistor), inductor, and a PWM (pulse-width modulation) controller with oscillator, amplifier, and comparator, etc. to efficiently transfer energy from the input to the output at periodic intervals. The fundamental boost converter and a buck converter containing a switched-mode power supply are studied. In this paper, the electrical characteristics of DC/DC power converters are simulated by program of SPICE, and the PWM controller is implemented to check the operation. In addition, power efficiency is analyzed based on the specification of each component.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2258-2271
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• 2016

In this paper, some crucial performance characteristics related to the operational reliability of the post-fault Pulse Width Modulated (PWM) rectifiers, such as line current harmonic distortion, Common Mode Voltage (CMV), and current stress on the capacitors, are fully investigated. The aforementioned performance characteristics of post-fault rectifiers are highly dependent on the utilized space vector modulation (SVM) schemes, which are also examined. Detailed analyses of the three most commonly used SVM schemes for post-fault PWM rectifiers are provided, revealing the major differences in terms of the zero vector synthesis approaches. To compare the performances of the three SVM schemes, the operating principles of a post-fault rectifier are presented with various SVM schemes. Using analytical and numerical methods in the time domain, the performances of the line current distortion, common mode voltage and capacitor current are evaluated and compared for each SVM scheme. The proposed analysis demonstrates that the zero vector synthesis approaches of the considered methods have significant impacts on the performance characteristics of rectifiers. In addition, the advantages and disadvantages of the proposed SVM schemes are discussed. The experimental results verify the effectiveness and validity of the proposed analysis.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.638-642
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• 2005

This paper proposes a modified space-vector pulse width modulation (PWM) strategy which can restrict the common-mode voltage for three-phase to three-phase matrix converter and still keep sinusoidal input and output waveforms and unity power factor at the input side. The proposed control method has been developed based on contributing the appropriate space vectors instead of using zero space vectors. The advantages of this proposed method is to reduce the peak value of common-mode voltage to 42% beside the lower high harmonic components as compared to the conventional SVM method. Hence, the new table is also presented with the new space vector rearrangement. Furthermore, the voltage transfer ratio is unaffected by the proposed method. A simulation of the overall system has been carried out to validate the advantages of the proposed method.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.96-97
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• 2019

Pulse Width Modulation (PWM) is a widely adopted technique to drive the motor using the voltage source inverters. Since they generate high frequency Common Mode (CM) Voltage, a high shaft voltage in induction motor is induced which leads to parasitic capacitive currents causing adverse effects such as premature deterioration of ball bearings and high levels of electromagnetic emissions. This paper presents an Active Cancellation Circuit (ACC) which can significantly reduce the CM voltage hence the common mode current in the three phase induction motor drives. In the proposed method the CM voltage is detected by the capacitors and applied to the frame of the motor to cancel the CM voltage hence the CM current. Unlike the conventional methods the proposed method does not insert the transformer in between the inverter and motor, a high power rating three phase transformer is not required and no losses associated with it. In addition the proposed method is applicable to any kind of PWM motor drives regardless of their PWM methods. The effectiveness of the proposed method is proved by the experiments with a three phase induction motor (1.1kW 415V/60Hz) combined with a three phase voltage source inverter modulated by the Space Vector Modulation (SVM).

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.6
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• pp.51-60
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• 2004

In this paper, we optimized the PDT laser system to improve the therapy effects of malignancies. In order to optimize, the variation of laser output and specific wavelength shift have to reduced. To improve the PDT therapy clinician require the diverse radiation mode which irradiate the tumor surface. Continuous wave mode that general application may causes tissue thermal damage not only to tumor tissue, but also to normal tissue. In this paper, therefore, we suggested new technique for radiation method to improved PDT effects and prevented to the thermal effects for the tissue. In the experimental we verified the stability of wavelength, laser output stability and proved the reduced thermal effects to the tissue using the pulse & burst radiation modes in vitro.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.8
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• pp.1407-1411
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• 2008

In material processing, a laser system with optimal laser parameters has been considered to be significant. Especially, the laser scribing technology is thought to be very important for fabricating DSSC(Dye sensitized solar eel!) modules with good quality. Moreover, the $TEM_{00}$ mode laser beam is the most dominant factor to decide the IPCE(Incident photon to current conversion efficiency) characteristics. In order to get the $TEM_{00}$ mode, a pin-hole is inserted within a simple pulsed Nd:YAG laser resonator. And the spatial field distribution is measured by using three size pin-hole diameters of 2.0, 6.0mm respectively. At that moment, each case has the same laser beam energy by adjusting the discharge voltage and pps(pulse per second). From those results, it is known that the pin-hole size of 2.0mm has the perfect $TEM_{00}$ mode. In addition, at the charging voltage of 1000V, 10pps and the feeding speed of 1.11mm/sec, the SEM photo of FTO(Fluorine-doped tin oxide) thin film layers shows the best scribing trace.

• Journal of Power Electronics
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• v.17 no.3
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• pp.641-652
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• 2017

This paper proposes a cost-effective topology to drive a three-phase open-end load based on a five-leg indirect matrix converter (IMC) and a space vector modulation (SVM) method. By sharing an inverter leg with two load terminals, the proposed topology can reduce the number of power switches when compared to topologies based on a direct matrix converter or a six-leg IMC. The new SVM method uses only the active vectors that do not produce common-mode voltage (CMV), which results in zero CMV across the load phase and significantly reduces the peak value of the CMV at the load terminal. Furthermore, the proposed drive system can increase the voltage transfer ratio up to 1.5 and provide a superior performance in terms of an output line-to-line voltage with a three-level pulse-width modulation waveform. Simulation and experimental results are given to verify the effectiveness of the proposed topology and the new SVM method.

• Transactions on Electrical and Electronic Materials
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• v.7 no.1
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• pp.7-11
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• 2006

The changes of the electrical conductivity in chalcogenide amorphous semiconductors, $Ge_{1}Se_{1}Te_{2}$, have been studied. A phase change random access memory (PRAM) device without an access transistor is successfully fabricated with the $Ge_{1}Se_{1}Te_{2}$-phase-change resistor, which has much higher electrical resistivity than $Ge_{2}Sb_{2}Te_{5}$ and its electric resistivity can be varied by the factor of $10^5$ times, relating with the degree of crystallization. 100 nm thick $Ge_{1}Se_{1}Te_{2}$ thin film was formed by vacuum deposition at $1.5{\times}10^{-5}$ Torr. The static mode switching (DC test) is tested for the $100\;{\mu}m-sized$ $Ge_{1}Se_{1}Te_{2}$ PRAM device. In the first sweep, the amorphous $Ge_{1}Se_{1}Te_{2}$ thin film showed a high resistance state at low voltage region. However, when it reached to the threshold voltage, $V_{th}$, the electrical resistance of device was drastically reduced through the formation of an electrically conducting path. The pulsed mode switching of the $20{\mu}m-sized$ $Ge_{1}Se_{1}Te_{2}$ PRAM device showed that the reset of device was done with a 80 ns-8.6 V pulse and the set of device was done with a 200 ns-4.3 V pulse.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.12
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• pp.1155-1164
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• 2011

In this paper, we proposed the transmit beam measurement method of active phased array antenna, which is installed in Korea's first developed naval medium range radar, using near-field measurement facility. The pulse-mode high power characteristics of active phased array antenna's trasmit-beam make it difficult to measure with general near-field measurement facilities where low power continuous RF signals are used. Thus, in this paper, the measurement method of active phased array antenna's transmit beam in conjunction with the near-field measurement facility, which is suitable for the high-power transmit beam measurement, and PNA-X network analyzer(Agilent Technologies), which can support pulse-mode measurement, was proposed and measured by near-field measurement techniques. And the EIRP(Effective Isotropic Radiated Power), the transmit characteristic of active phased array antenna, was measured by the near field measurement techniques and compared to numerical estimation which was nearly equal with small difference of 0.1 dB.