• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.5-9
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• 2003

Conventional variable-speed Induction motor drives with inverters are subject to detrimental effect of zero-sequence voltages, such a shaft voltage and bearing current. This paper presents a way of the suppression of the zero-sequence components in multilevel H-bridge inverters. First examined Is the inherent zero-sequence characteristic of the conventional subharmonic PW method. Then it is shown that the zero-sequence voltage can be eliminated with proper -selection of switching states with space vector modulation. Although this method alone restricts the linear modulation range of control, a combination of the proposed method and the minimum switching method appears to be effective in suppressing the zero-sequence voltage to minimum level while maintaining the linear control range.

• Journal of Power Electronics
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• 제7권4호
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• pp.294-300
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• 2007

This paper deals with a design of a bootstrap power supply using snubber energy regeneration, which is used to power a high-side gate driver of a half-bridge circuit. In the proposed circuit, the energy stored in the low-side snubber capacitor is transferred to the high-side bootstrap capacitor without any magnetic components. Thus, the power dissipation in the RCD snubber can be effectively reduced. The operation principle and design method of the proposed circuit are presented. The experimental results are also provided to show the validity of the proposed circuit.

• 한국정밀공학회지
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• 제16권7호
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• pp.51-57
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• 1999

Recently, long large bridges are built for mass transportation. Movable bearing shoes are important components of the bridges because they support movement of translation and rotation of bridge. In design stage of the long large bridges, detailed analyses using the finite element method are performed to guarantee safety and reliability. For that purpose, three-dimensional modeling is carried out by I-DEAS software and finite element analysis by ANSYS software. Results of the analyses are reviewed and important design factors for movable bearing shoes are discussed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.22-24
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• 2006

Of all the proposed resonant techniques, the well-known phase-shifted full bridge converter remains one of the most attractive because it offers an easy way of achieving ZVS with a minimum of extra components added, which is essential for the high power applications. This paper describes the design of a digital controller for a Phase Shifted Full-bridge PWM Converter. The small-signal model is derived incorporating the effects of phase-shift control and the utilization of the transformer leakage inductance and power FET junction capacitances to achieve the zero-voltage resonant switching. Based on the derived small-signal model, the digital controller is designed in the discrete domain. The performance of designed controller is verified through the simulation.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1350-1358
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• 2008

Recently the study related to life cycle cost analysis of railway structure consisted of a complex is proceeded covering several range, which is considering the methodology of efficiency and rationalization for maintenance and analysing long-time behavior of the structure of looking at standpoint from asset management and safety. But LCCA(life cycle cost analysis) of railway structure was almost impossible as there were not anything datum for maintenance plan, such as maintenance periods related to each of components(painting and corrosion of steel, and cracking of elements, etc)and maintenance proportion, despite of its 100-year history. According, for collecting data related to railway truss bridge, bridge record cards and testing safety papers, and researching question, etc are surveyed and classified for LCC Analysis. Especially, LCC assessment on the side of assets-maintenance considering about initial cost, maintenance cost, and indirect cost is constructed. Maintenance period and complementary measure rate are very important in maintenance. To decide maintenance period, Baysian updating method is applied.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.454-461
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• 2001

Dynamic responses of a multi-span simply supported bridge are examined under seismic excitations considering damage of bearings. An idealized mechanical model which can consider components such as pounding, friction at the supports, abutment-soil interaction, rotational and translational motions of foundations, and the nonlinear pier motions, is developed to analyze the effects due to damage of bearings. It is assumed that the bearing's response after failure can be expressed with a sliding model with a friction coefficient between the superstructure and the pier top. It is found that the global seismic behaviors are significantly influenced by the damage of bearings and the damage of bearings may lead to unseating failure at unpredicted supports. Therefore, It can be concluded that detailed seismic response analyses of bridge systems considering damage of bearings is required for the purpose of the seismic safety evaluation.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권3호
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• pp.366-371
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• 2012

In this paper, we propose an electric circuit using one common-arm of H-Bridge inverters to reduce the number of switching components in the multi-level inverter combined with H-Bridge inverters and transformers. And furthermore, we suggested a new multi-level PWM inverter using PWM level to reduce THD (Total Harmonic Distortion). We use a phase-shift switching method that has the same rate of usage at each transformer. Also, we test the proposed prototype 9-level inverter to clarify the proposed electric circuit and reasonableness of the control signal for the proposed multi-level PWM inverter.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.663-666
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• 2004

An analysis of the annual frequency of collapse(AF) is performed for each bridge pier exposed to ship collision. AF is computed for each bridge component and vessel classification. The summation of AFs computed over all of the vessel classification intervals for a specific component should equal the annual frequency of collapse of the component. The designer should use judgment in developing a distribution of the vessel frequency data based on discrete groupings or categories of vessel size by DWT. In the present study the effect of vessel classification on the annual frequency of collapse in the ship collision risk assessment is investigated by illustrative numerical examples based on the vessel frequency data of the domestic harbor. The DWT interval for larger vessels has more effect on the ship collision risk. Therefore the expert judgement in determining the larger DWT interval is required because the design impact lateral resistances of bridge components depend on the ship collision risk.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.591-594
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• 2004

Recently, a tendency for development of seismic approach of foreign countries is capacity design development. Capacity design is rational seismic design concept of capacity protection considering not only earthquake magnitude, but also behavior of structure. For that reason, the most bridge seismic design specifications contain capacity protection provisions explicitly or implicitly. The capacity protection is normally related with slenderness effect of the columns, force transfer in connections between columns and adjacent elements, and shear design of columns. It intends to prevent brittle failure of the structural components of bridges, so that the whole bridge system may show ductile behavior and failure during earthquake events. The objectives of this paper are to deduce needed provisions for the moderate seismicity regions such as Korea after studying current seismic design codes and to establish rational criteria provisions of seismic design for future revision of seismic design specifications.

• Journal of Power Electronics
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• 제16권1호
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• pp.173-181
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• 2016

In this paper, a new technique for harmonic optimization in cascaded H-bridge 7-level inverters is proposed. The suggested strategy is based on minimizing an objective function which simultaneously optimizes the converter utilization and Total Harmonic Distortion (THD). The Switch Utilization Ratio (SUR) is formulized for both the phase and line-line voltages of a 7-level inverter and is considered in the final objective functions. Based upon the SUR formula, utilization ratio enhancement will reduce the value of feeding DC links, which improves the efficiency and lifetime of the circuit components due to lower voltage stresses and losses. In order to achieve more effective solution in different modulation indices, it is assumed that the DC sources can be altered. Experimental validation is presented based on a three-phase 7-level inverter prototype.