• Journal of Navigation and Port Research
• /
• v.33 no.3
• /
• pp.227-233
• /
• 2009

This experimental study has been carried out to investigate the reduction in side friction of open caisson using air-jet method. For this study, the large size caisson having air-pockets was used. This caisson was used as substructure of bridge. By using air-jet method, settlement time was decreased and even settlement was reached to the depth which conventional methods could not be. We found that the side resistance decreases to less then half the expected value. In addition to these merits, the air-jet method can result in self-weight settlement without applying additional load. Also the open caisson damage caused by blasting can be prevented with this method.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.10 no.2
• /
• pp.194-202
• /
• 2005

This paper proposes a new multi-level energy recovery sustaining driver for AC PDP(Plasma Display Panel), which solves the problems and maintains the merits of the conventional multi-level sustaining driver. While the conventional circuit improves the hard switching in the Weber circuit, there exist parasitic resonant currents in resonant inductors and Vs/2 sustaining period. Comparing the proposed circuit with the conventional circuit, the number of inductors are reduced by half, the parasitic resonant currents in resonant inductors are eliminated, and the hard switching problem is solved by CIM(Current Injection Method). Moreover the voltages across series-connected switching elements in the full bridge circuit are distributed equally by adopting NPC(Neutral Point Clamping) techniques. And circuit operations of the proposed circuit are analyzed for each mode and the validity is verified by the simulations using PSpice program and experimentation with a prototype drive circuit.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.10 no.4
• /
• pp.313-322
• /
• 2005

In this paper, High power factor electronic ballast using a double resonant Inverter for 250[W] MHD lamp is designed and implemented. Proposed electronic ballast is composed of configuration that is cascaded boost active PFC circuit as power factor corrector and half-bridge double resonant inverter Into two stage approach. Theoretical analysis of circuit and characteristics estimation is generally illustrated by using normalized parameter. To remove the phenomenon of acoustic resonance in the lamp, Simple frequency controller composed timer IC and driving IC is designed and employed on the ballast. The experimental results show that an high power factor electronic ballast using a double resonant inverter is operated stably.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.10 no.4
• /
• pp.356-362
• /
• 2005

In this paper, in order to develop a simple and high efficient ballast without an external ignitor, a half-bridge type ballast with a coupled inductor and a frequency controlled synchronous rectifier is proposed. The Internal LC resonance of the buck converter is used to generate a high voltage pulse for the ignition, and the coupled inductor filter is used for steady state ripple cancellation. Also, a synchronous buck converter is applied for the DC/DC converter stage. In order to improve the efficiency of the ballast, a frequency control method is proposed. This scheme reduces a circulation current and trun off loss of the MOSFET switch on the constant power operation, which results in increase of the efficiency of the ballast system about 4$\%$, compared to a fixed frequency control. It consists a 2-stage version ballast with a PFC circuit. The results are verified nth hardware experiments.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.8 no.6
• /
• pp.504-511
• /
• 2003

In this paper, inverter type neon power supply using a piezoelectric transformer is fabricated and its characteristic is investigated. Developed neon power supply is composed of basic circuit and blocks, such as rectifier part, frequency oscillation part and piezoelectric transformer and resonant half bridge inverters. In this paper for complement the low power limitation, piezoelectric transformer at parallel connected driving by inverter is studied for noon tubes system of high power. When piezoelectric transformer is connected with parallel, LC filter connection method with parallel and selection of inductance L and capacitor C of primary side is suggested for reduce unbalanced current at the terminal of each transformer. Piezoelectric transformers use piezoelectric ceramic devices. Thus it is wireless therefore it has high power density, high Isolation level, low loss, more light, and miniaturization. In addition, high voltage transfer ratio is expected because there is no leakage inductance. Also, it has economic merit that the electrical loss Is low because structure is simple, small and tighter weight.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.16 no.3
• /
• pp.20-28
• /
• 2002

This paper describes the time sharing type high frequency resonant inviter can be used as power of induction heating. This closed inverter can be obtained output frequency three times than switching frequency by composing three unit inviter of conventional Half-Bridge serial resonant inverter in parallel with input power source also, this reduce switching loss because it has ZVS function. The analysis of the proposed circuit is generally described by using the normailized proposed parameters. The principle of basic operating and the its charasteristics are extimated by the parameters such as switching frequency($\mu$), the variation of Phase angle($\phi$) of Phase-shift. Experimental results are presented to verify theoretical discussion. This preposed inverter will be able to be prastically used as a power supply in various fields as induction, heating application, DC-DC converter etc.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.6 no.5
• /
• pp.423-431
• /
• 2001

This paper proposes a new active common-mode voltage damper circuit that is capable of suppressing a common-mode voltage produced in the PWM VSI-fed induction motor drives. The new active common mode voltage damper is consists of a four-level half-bridge Inverter and a common mode transformer with a blocking capacitor. In order to reduce the common mode voltage and high frequency leakage current the active common mode damper applies to the PWM inverter system the compensated voltage of which the amplitude is the same as the common mode voltage and of which the polarity is opposite to the common mode voltage. Simulated using P-SPICE and experimental results show that common-mode voltage damper makes contributions to reducing a high frequency leakage current and common-mode voltage.

• Journal of Korean Academy of Fundamentals of Nursing
• /
• v.13 no.2
• /
• pp.242-248
• /
• 2006

Purpose: The purpose of this study was to identify the effects of a BeHaS exercise program on pain, health status, body weight in middle-aged women who have osteoarthritis in their knees. Method: The participants in this study were eighteen women whose mean age was 56.22years and who had osteoarthritis in the knees. The BeHaS exercise program consists of approximately one and half hour of exercise, two days per week, for twelve weeks. Data were gathered from September 2005 to December 2005 using a questionnaire and measuring VAS for pain, KWOMAC for health status, body weight for scale. Data were analyzed with the SPSS Win 11.0 using frequency and paired t-test for differences between pre-exercise and post-exercise. Results: The results of this study are as follows: Scores for pain on post test were statistically lower than pre test(t=4.202, p=0.001), health status was statistically improved after exercise program (t=3.479, p=0.002). But body weight did not change(t=-.774, p=0.222). Conclusion: From these results, it is concluded that the BeHaS exercise program can be effective in decreasing pain and increasing health status in middle-aged women with knee osteoarthritis.

• Journal of Power Electronics
• /
• v.19 no.4
• /
• pp.922-933
• /
• 2019

The arm inductance (AI) of a modular multilevel converter (MMC) affects both the fault and circulating current magnitudes. In addition, it has an impact on the inverter efficiency and harmonic content. In this study, the AI of a three-phase MMC is optimized in a novel way in terms of DC voltage utilization, harmonics and efficiency. This MMC has 10 submodules (SM) per arm and the power circuit topology of the SM is a half-bridge. The optimum AI is adopted and verified in an MMC that has 100 SMs per arm. Then the phase shift (PS) and phase disposition (PD) pulse width modulation (PWM) methods are investigated for better DC voltage utilization, efficiency and harmonics. It is found that similar performances are obtained for both modulation techniques in terms of DC voltage utilization. However, the total harmonic distortion (THD) of the PS-PWM is found to be 0.02%, which is slightly lower than the THD of the PD-PWM at 0.16%. In efficiency calculations, the switching and conduction losses for all of the semiconductor are considered separately and the minimum efficiency of the 100-SM based MMC is found to be 99.62% for the PS-PWM and 99.64% for the PD-PWM with the optimal value of the AI. Simulation results are verified with an experimental prototype of a 6-SM based MMC.

• Journal of Convergence for Information Technology
• /
• v.8 no.6
• /
• pp.187-192
• /
• 2018

This thesis is about the study of inverter terminal boxes in a explosion proof type exhaust fan that can control wind volume and operating time. In Korea, there is no ventilator to adjust the amount of wind and operating time when working in poor conditions. The purpose of the project is to create a explosion terminal box that can control the operating time and wind speed of a suitable explosion ventilator in hazardous environments. The two explosion-proof switches allow the operation time to be driven 1 hour, 3 hours and continuous time, and the speed of the induction motor rotation was set in 3 stages at 2000 rpm, 2600 rpm and 3000 rpm to control the volume. The tested motor used a half-horsepower barrier three-phase induction motor and a full-bridge inverter to set the desired flow rate and operating time.