• Journal of Power Electronics
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• 제16권3호
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• pp.849-860
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• 2016

The high-switching-frequency operation of power converters can achieve high power density through size reduction of passive components, such as capacitors, inductors, and transformers. However, a small-output capacitor that has small capacitance and low effective series resistance changes the small-signal model of the converter power stage. Such a capacitor can make the converter unstable by increasing the crossover frequency in the transfer function of the small-signal model. In this paper, the design and implementation of a high-frequency LLC resonant converter are presented to verify the power density enhancement achieved by decreasing the size of passive components. The effect of small output capacitance is analyzed for stability by using a proper small-signal model of the LLC resonant converter. Finally, proper design methods of a feedback compensator are proposed to obtain a sufficient phase margin in the Bode plot of the loop gain of the converter for stable operation at 500 kHz switching frequency. A theoretical approach using MATLAB, a simulation approach using PSIM, and experimental results are presented to show the validity of the proposed analysis and design methods with 100 and 500 kHz prototype converters.

• Structural Engineering and Mechanics
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• 제28권6호
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• pp.677-694
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• 2008

A vibration power minimization model is developed, based on the mobility matrix method, for a vibration isolation system consisting of a vibrating source placed on an elastic support structure through multiple resilient mounts. This model is applied to investigate the design optimization of an X-Y motion stage-based vibration isolation system used in semiconductor wire-bonding equipment. By varying the stiffness coefficients of the resilient mounts while constraining the dynamic displacement amplitudes of the X-Y motion stage, the total power flow from the X-Y motion stage (the vibrating source) to the equipment table (the elastic support structure) is minimized at each frequency interval in the concerned frequency range for different stiffnesses of the equipment table. The results show that when the equipment table is relatively flexible, the optimal design based on the proposed vibration power inimization model gives significantly little power flow than that obtained using a conventional vibration force minimization model at some critical frequencies. When the equipment table is rigid enough, both models provide almost the same predictions on the total power flow.

• 한국통신학회논문지
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• 제18권4호
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• pp.499-508
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• 1993

이 논문에서 CATV 및 MATV시스템용으로 널리 쓰이는 전력분배기의 설계법과 주파수특성해석을 다루고 있다. 즉, 윌킨슨형 파워디바이더를 집중정수회로화하여 CATV주파수대에 적합한 2분배기의 설계법을 이론적으로 고찰하고, 주파수특성을 해석하고 있다. 윌킨슨형 파워디바이더의 분배특성을 향상시키기 위해 보상회로를 부가한 최적설계법을 제시하여 특성평가를 하였으며, 그 결과 특성이 크게 향상됨을 이론적인 고찰과 실험을 통하여 증명하였다.

• 대한조선학회논문집
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• 제53권2호
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• pp.108-114
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• 2016

Recently, there has been a growing interest in marine leisure sports and high speed power boat for fishing. The prototype of 20 feet class power boat was developed and authors are joined in this government-led project. The research was performed to evaluate the optimal structure and design of the structural strength necessary to ensure the structural safety of the power boat. A new material ROCICORE fiber added to the mat and roving was adopted for high-power tenacity. ANSYS Workbench has been used to make the structural model, evaluate the strength and optimize the structural design. The response of the structure to quasi-static slamming loads according to the rules and regulations of ISO 12215-5, Lloyd’s Register of Shipping and Korean Register has been implemented and studied. An optimization study for the structural response is carried out by changing the plate thickness and section modulus of stiffeners. The power boat structure derived fuel efficiency is optimized by performing the best possible structural design to minimize the hull weight.

• 한국초전도ㆍ저온공학회논문지
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• 제22권4호
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• pp.31-39
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• 2020

Power cables made of high temperature superconductors (HTS) are considered as most advanced applications of superconductivity for electro-energetics. Several cables made of the First Generation (1G) HTS wires have been produced and installed to electrical grids worldwide. Power cables made of the Second Generation HTS wires (2G or Coated Conductors) are in active development. Most basic principles of HTS power cables development have been published in many works since 90-ties. In this Review we would like to present our new developments mostly directed to 2G HTS compact power cables. We are presenting the methods to optimize a design of 2G AC compact power cable providing uniform current distribution among cable layers and the production technology approaches to implement such a design. AC losses measurements in such cables and other test methods are described. Some problems of the development 2G HTS power cables with small diameters are discussed. We presented as examples designs, developments and test results of two major coaxial cables designs: single-phase (cable core and a shield) and three-phase (triaxial: with three coaxial phases).

• ETRI Journal
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• 제45권4호
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• pp.570-580
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• 2023

Sensor nodes are the most significant part of a wireless sensor network that offers a powerful combination of sensing, processing, and communication. One major challenge while designing a sensor node is power consumption, as sensor nodes are generally battery-operated. In this study, we proposed the design of a low-power, long range-based wireless sensor node with flexibility, a compact size, and energy efficiency. Furthermore, we improved power performance by adopting an efficient hardware design and proper component selection. The Nano Power Timer Integrated Circuit is used for power management, as it consumes nanoamps of current, resulting in improved battery life. The proposed design achieves an off-time current of 38.17309 nA, which is tiny compared with the design discussed in the existing literature. Battery life is estimated for spreading factors (SFs), ranging from SF7 to SF12. The achieved battery life is 2.54 years for SF12 and 3.94 years for SF7. We present the analysis of current consumption and battery life. Sensor data, received signal strength indicator, and signal-to-noise ratio are visualized using the ThingSpeak network.

• Journal of Power Electronics
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• 제19권3호
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• pp.815-826
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• 2019

This paper discusses a simple control approach for a Unified Power Conditioner (UPC) system to achieve power quality compensation at the point of common coupling in distribution systems. The proposed Instantaneous Power Estimation Algorithm (IPEA) for shunt and series active power filters uses a simple mathematical concept that reduces the complexity in the design of the controller. The performance of a UPC is verified with a system subjected to voltage distortions, sags/swells and unbalanced loads using MATLAB/SIMULINK. The simulation study shows that a UPC with the proposed control algorithm can effectively compensate for voltage and current harmonics, unbalance and reactive power. The control algorithm is experimentally implemented using dSPACE DS1104 and its effectiveness has been verified.

• 전기학회논문지
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• 제58권1호
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• pp.199-202
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• 2009

Scan design is currently the most widely used structured Design For Testability approach. In scan design, all storage elements are replaced with scan cells, which are then configured as one or more shift registers(also called scan chains) during the shift operation. As a result, all inputs to the combinational logic, including those driven by scan cells, can be controlled and all outputs from the combinational logic, including those driving scan cells, can be observed. The scan inserted design, called scan design, is operated in three modes: normal mode, shift mode, and capture mode. Circuit operations with associated clock cycles conducted in these three modes are referred to as normal operation, shift operation, and capture operation, respectively. In spite of these, scan design methodology has defects. They are power dissipation problem and test time during test application. We propose a new methodology about scan shift clock operation and present low power scan design and short test time.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.415-419
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• 2015

Engineering is a value-adding process applying knowledge and skills in the construction industry that includes the planning, feasibility study, project management (PM), front end engineering and design (FEED), detail design, procurement, construction, supervision, and operation. Among these engineering activities, FEED is defined as a comprehensive design practice in the early design phase focused on conceptual design and basic design. It is a particularly influencing area that determines the competitiveness of procurement and construction capability of construction firms (KNIN 2013). Nevertheless, previous studies in FEED have been limited to the design process, deliverable, or particular management technique (e.g. system engineering, collaboration, information etc.). In this context, the purpose of this study is to propose a comprehensive FEED business process structure for project management of thermal power plant construction projects encompassing the entire project life cycle. And an assessment methodology for FEED functions was developed. It is expected that the proposed structure of FEED functions and FEED evaluation methodology will contribute to improvement of competitive capability of engineering, procurement, and construction (EPC) companies.

• Journal of Electrical Engineering and Technology
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• 제7권2호
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• pp.178-183
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• 2012

The design of the integrated quench protection (QP) system for the high current superconducting magnet (SCM) has been fabricated and tested for the toroidal field (TF) coil system of the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The QP system is capable of protecting the TF SCM, which consists of 16 identical coils serially connected with a stored energy of 495 MJ at the design operation level at 35.2 kA per turn. Given that the power supply for the TF coils can only ramp up and maintain the coil current, the design of the QP system includes two features. The first is a basic fast discharge function to protect the TF SCM by a dump resistor circuit with a 7 s time constant in case of coil quench event. The second is a slow discharge function with a time constant of 360 s for a daily TF discharge or for a stop demand from the tokamak control system. The QP system has been successfully tested up to 40 kA with a short circuit and up to 34 kA with TF SCM in the second campaign of KSTAR. This paper describes the characteristics of the TF QP systems and test results of the plasma experiment of KSTAR in 2009.