• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.82-85
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• 2000

We introduce pulsed $CO_2$ laser power supply excited by half-wave rectified 60Hz AC discharge some advantage of cost and size compared to a typical pulsed power supply. AC frequency is adjusted from 10Hz to 60Hz to control laser output. In this laser, a low voltage open loop control for high voltage AC discharge circuits is employed to avoid the HV sampling or switching. The control is achieved by using a ZCS circuit and a PIC one-chip microprocessor that control the gate signal of SCR precisely. The pulse repetition rate is limited by 60Hz due to a high leakage inductance. The maximum laser output was obtained about 20W at the condition of total pressure, 18Torr and pulse repetition rate,60Hz.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.6
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• pp.626-629
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• 1991

The negative wire of an electrolytic ozone generator, proposed by authors, has been contaminated by attaching the impurity particulate in tap water, which is called BUILD-UP phenomenon. The higher applied voltage and the larger wire diameter have shown the higher build-up rate, which makes the current reducing largely and concurrently the ozone production smaller. It is found that the positive electrode of the ozone generator has a strong SELF-CLEANING effect by detaching the impurity particulate from its surface, which, however, is used us a novel means of solving the build-up problem. As a result, the build-up problem can be solved effectively by applying an alternate square wave pulse voltage to the electrodes so as to get the self-cleaning ability on the both electrodes during each of the half pulse duration time.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2019_2020
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• 2009

A recurrent surge oscillograph(RSO) test was performed at the Taean thermal power plant on #5 turbine generator. The test was conducted using a rotor reflectometer and digital oscilloscope. A DC voltage step is applied to each end of the rotor winding in turn. Each reflected wave, at the input end of the winding, is monitored and the two waveforms are superimposed automatically and monitored on a single channel oscilloscope. As the half windings in a rotor are identical, the two waveforms monitored at each end of the rotor will also be identical for a healthy winding. A winding with a fault will cause different voltages to be monitored at the two ends.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1929-1931
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• 1996

In this work, it is proposed new PD(partial discharge) detection technique using electro-optic effect, for which partial discharges generated from needle-plane electrode in air were detected through optical measuring system by use of $LiNbO3_3$ electro-optic crystal. As a result, it is noticed that PD measurable phase intervals are limited by the asymmetrical D-E hysteresis loop of the crystal with defects and half-wave voltage. However, both number of measured PD pulses and their amplitude were increased with applied voltage, which likely implies that it is possible to detect PD through newly proposed electro-optic method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.6
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• pp.475-482
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• 2020

For electronic paper displays using electrophoresis, the response time and reflectivity of the image panel fabricated by filtering are analyzed. For the filtering process, a square wave and ramp wave are applied to white charged particles with a unique q/m value. We divide the sample panels into #1 to #4 according to the applied waveform in the filtering process. Step waves comprising two steps are used to drive the panel; therefore, we divide the driving conditions into D1~D4. The applied voltage at the first stage of the half cycle of the driving waveform moves the charged particles attached via the image force from the electrode, and the applied voltage at the second stage moves the floating charged particles by detaching. As mentioned, four types of driving conditions (D1 to D4) classified according to the half cycle of the driving waveform are applied to the samples #1 to #4), which are classified according to four types of filtering process. When driving condition D1 is applied to the four types of sample panels, the rise time of #1 is 1.59s, #2 is 1.706s, #3 is 1.853s, and #4 is 1.235s, resulting in #4 being relatively faster compared with other sample panels, and showing the same trend in other driving conditions. As a result, we confirm that applying the driving condition D1 causes abrupt movement of the white charged particles injected into the cell. When the same driving waveform (D1) is applied to each sample, reflectivities of 32.1% for #1, 31.4% for #2, 27.9% for #3, and 63.4% for #4 are measured. From the experiment, we confirm that the driving condition D1 (1s of 3.5 V, 9s of 3.0 V) and ramp wave #4 in filtering are desirable for good reflectivity and response time. Our research is expected to contribute to the improvement of the filtering process and optimization of the driving waveform.

• Journal of information and communication convergence engineering
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• v.15 no.4
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• pp.199-204
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• 2017

A compact dual-band half-ring-shaped (HRS) bent slot antenna fed by a coplanar waveguide for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications is presented. The antenna consists of two HRS slots with different lengths and widths. The two HRS slots are connected through an arc-shaped slit, and the upper HRS slot is bent in order to reduce the size of the antenna. The optimized dual-band HRS bent slot antenna operating in the 2.45 GHz WLAN and 3.5 GHz WiMAX bands is fabricated on an FR4 substrate with dimensions of 30 mm by 30 mm. The slot length of the proposed dual-band slot antenna is reduced by 35%, compared to a conventional dual-band rectangular slot antenna. Experimental results show that the proposed antenna operates in the frequency bands of 2.40-2.49 GHz and 3.39-3.72 GHz for a voltage standing wave ratio of less than 2, and measured gain is larger than 1.4 dBi in the two bands.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.203-205
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• 2006

This paper presents a novel soft-switching PWM utility frequency AC to high frequency AC power conversion circuit incorporating boost-half-bridge inverter topology, which is more suitable and acceptable for cost effective consumer induction heating applications. The operating principle and the operation modes are presented using the switching mode and the operating voltage and current waveforms. The performances of this high-frequency inverter using the latest IGBTs are illustrated, which includes high frequency power regulation and actual efficiency characteristics based on zero voltage soft switching (ZVS) operation ranges and the power dissipation as compared with those of the previously developed high-frequency inverter. In addition, a dual mode control scheme of this high frequency inverter based on asymmetrical pulse width modulation (PWM) and pulse density modulation (PDM) control scheme is discussed in this paper in order to extend the soft switching operation ranges and to improve the power conversion efficiency at the low power settings. The power converter practical effectiveness is substantially proved based on experimental results from practical design example.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.387-390
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• 2006

This paper presents a novel soft-switching PWM utility frequency AC to high frequency AC power conversion circuit Incorporating boost-half-bridge inverter topology, which is more suitable and acceptable for cost effective consumer induction heating applications. The operating principle and the operation modes are presented using the switching mode and the operating voltage and current waveforms. The performances of this high-frequency inverter using the latest IGBTs are illustrated, which includes high frequency power regulation and actual efficiency characteristics based on zero voltage soft switching (ZVS) operation ranges and the power dissipation as compared with those of the previously developed high-frequency inverter. In addition, a dual mode control scheme of this high frequency inverter based on asymmetrical pulse width modulation (PWM) and pulse density modulation (PDM) control scheme is discussed in this paper in order to extend the soft switching operation ranges and to improve the power conversion efficiency at the low power settings. The power converter practical effectiveness is substantially proved based on experimental results from practical design example.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.798-802
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• 2013

In a conventional DC power supply used for CO2 laser, the circuit elements such as a rectifier bridge, a current-limiting resistor, a high voltage switch, energy storage capacitors ans a high-voltage isolation transformer using high turn ratio are necessary. Consequently, those supplies are expensive and require a large space. Thus, laser resonator and power supply should be optimally designed. In this paper, we propose a new power supply using high frequency resonance phenomena for CW(Continuous wave) CO2 laser (maximum output of 23W with discharge length of 450mm). It consists of a transformer including leakage inductance, magnetizing inductance and half-bridge converter, a three-stage Cockcroft-Walton and PFC(Power factor correction) circuit. The output ripple voltage can be controlled the minimum of 0.24% under the high frequency switching of 231kHz. Furthermore, the output efficiency was improved to 16.4% and the laser output stability of about 5.6% was obtained in this laser system.

• Journal of radiological science and technology
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• v.20 no.2
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• pp.44-48
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• 1997

For the efficient management of the diagnostic x-ray equipment, a nation-wide inspection of hospitals was performed by an inspection institute in Taejon in the first half of 1997. Among those hospitals inspected, 28 equipments(machines) which were over 500 mA were randomly selected according to their characteristics : 7 condenser type x-ray equipments, 7 three control phase of full wave rectification of type remote control x-ray equipments, 7 single phase of full wave rectification type for general radiography equipments, and 7 single phase of full wave rectification type of R/F equipments. We obtained the following results by conducting the experiment based on the efficiency of the equipments mentioned above. 1) When the equipments are analyzed, 2 out of 7 single phase of full wave rectification type of general radiography equipments(28.6%), 3 out of 7 single phase of full wave rectification type of R/F equipments(42.9%), 5 out of 7 three phase of full wave rectification type remote of control x-ray equipments(71.4%), and 4 out of 7 condenser type of x-ray equipments(57.1%) showed suitability. It proves the superiority of the three phase of full wave rectification type of remote control x-ray equipments. 2) From the overall analysis, only about 50% of the equipments(suitability of 14 out of 28) maintain the efficient management. Therefore, maintenance management of equipments is more necessary. If the efficiency of the x-ray equipment is uniformly maintained and managed to prevent the breakdown(trouble) beforehand especially through the continuous inspection of tube voltage, tube current, exposure time, and collimator, the financial loss and exposure dose to the patient, as well as the workers engaged in radiation, can be reduced for better medical service.