• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.717-720
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• 2005

Acoustic loads generated by a rocket propulsion system cause severe random vibrations on payloads. In developing a new launch vehicle, a random vibration level must be specified before the detailed design of payloads or electronic equipments. This paper deals with prediction procedures of a random vibration level on payload section of KSLV-I. The prediction is based on statistical energy analysis. In order to verify the prediction methodology, test and analysis on a sub-scale payload section are performed. The predicted results subject to very high level of acoustic loads show a good agreement with the test results performed in the high intensity acoustic chamber. The predicted random vibration level on payload section of KSLV-I is also presented in this paper.

• Journal of Applied Reliability
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• v.11 no.1
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• pp.97-110
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• 2011

BLDC(Brushless Direct Current) motor is a powerful device to control the automotive electronic components used in green cars such as HEV/EVs(Hybrid Electric Vehicle and Electric Vehicle). This study is to propose reliability test items derived through pretesting, suitability analysis abd classification of previous BLDC motor tests. For environmental stress tests are determined by analysing environmental conditions and relevant failure mechanisms induced by climate loads, mechanical loads, chemical loads, etc. ATL and HALT are also considered for life testing and screening.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.1
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• pp.155-161
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• 2005

Nonlinear electronic loads used at office buildings distort the voltage and current waveform that cause the overheating of transformer losses, ELB(Electrical Leakage Breaker) tripping, and so on. This paper analyzed waveform distortion characteristics at several once buildings by comparing with magnitude of voltage and current harmonics, crest factor of voltage and current, phase voltage and current unbalance. As a consequence, severe current waveform distortion in phase and neutral line by harmonics and high current unbalance rates by unbalanced using of single loads among the three phases are investigated. The results of the study can be used in making decisions regarding reasonable and economical operating of loads at office buildings.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.12
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• pp.104-110
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• 2019

A nanosatellite designed by the Korea Microgravity Science Laboratory (KMSL) is currently under development. The KMSL nanosatellite is designed to perform two different scientific missions in space. To successfully complete missions, a variety of tests must be conducted to verify the performance of the designed satellite before launch. As part of the qualification test campaign, the KMSL nanosatellite underwent high level vibrational tests (to comply with Falcon 9 qualification level) to demonstrate the integrity of the system. The purpose of this study is to demonstrate that the primary structure and all electronic and mechanical components can withstand the vibrations and the loads experienced during the launch period. To this end, the KMSL nanosatellite was exposed to static and dynamic loads and various types of vibrations that are inevitably produced during the space vehicle launch period. The vibration test results clearly demonstrated that all avionics and mechanical components can withstand the vibrations and the loads applied to the KMSL nanosatellite's body through a Pico-satellite Orbital Deployer (POD).

• Electric Engineers Magazine
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• v.228 no.8
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• pp.43-48
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• 2001

Wide use of non-linear loads such as personal computers, monitors, laser printers, variable speed drives, UPS systems and other electronic equipment have led to harmonics becoming #1 issue in the electrical industry today. Commercial and Industrial building power distribution systems, designed for the old, linear-style loads especially when found in high densities. Some common power system problems include overloaded neutral conductors, overheated distribution transfOlmers, high neutral-to-ground voltage, poor power factor and distortion of the voltage waveform supplying these loads. The power quality problems, particularly high voltage distortion, have been known to cause equipment downtime due to malfunctions and component failure.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.2
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• pp.45-52
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• 2002

Load modeling is classified into two methods according to approaching method, so called the measurement and component-based method. The measurement method is to model the load characteristics measured directly at substations and feeders. But it is difficult to measure continuously load characteristics from naturally occurring. system variation. The component-based method consists of the fellowing process; component load modeling, composition rate estimation and aggregation of component loads, etc. In this paper, the characteristic experiment of component loads was performed to obtain data for the component load modeling as the component-based method. At first, representative component loads were selected by the proposed method considering the accuracy of load modeling and the performance possibility of component load experiment in the laboratory. Also an algorithm was Proposed to identify the reliability of data obtained from the component load characteristic experiments. In addition, the results were presented as the case studies.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.1
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• pp.34-41
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• 2016

This study investigates transformer losses caused by current harmonics. Electrical transformers are designed to work under sinusoidal voltage and current waves at a rated frequency. Recently, various nonlinear loads, such as power electronic converters, are connected to a power system; these converters generate current harmonics. Current harmonics increase power loss in transformers, which results in several problems, including temperature increase of the transformer and insulation damage. These problems will eventually shorten the operational life of the transformer. In this study, different types of losses caused by current harmonics in three-phase transformers are studied under linear and nonlinear load conditions. Linear loads are simulated and experimented on using pure resistance load, whereas nonlinear loads are simulated and experimented on using a three-phase twelve-pulse thyristor full-bridge rectifier. The different types of losses in three-phase transformers are evaluated analytically through the experimental result and simulation in PSiM.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.660-667
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• 2001

Power electronics plays an important role in providing an interface between fuel cells and loads. Furthermore, power electronic converters ensure that the power is reliably and efficiently delivered to the load in the required DC or AC form. In this paper, major types of fuel cells are presented. Basic structures, operating principles, and different applications of fuel cells are described. In addition, current status and future trends in the areas of power electronics for fuel cell applications are explained. A review of fuel cell power electronic system topologies and basic requirements are given as well.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.673-676
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• 2001

The photovoltaic power generation system has a great future as clean energy instead of fossil fuel, which has many environmental problems such as exhausted gas or air pollution. In a utility interactive photovoltaic generation system, a three phase inverter is used for the connection between the photovoltaic array and the utility. This paper presents a three phase inverter for photovoltaic power system with current controller, voltage controller, PLL control system and the phase detector of interactive voltage by using dq transformation. The proposed inverter system provides a sinusoidal ac current for domestic loads and the utility line with unity power factor.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2254-2261
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• 2018

This paper analyzes stability of current control in respect of four cases of battery energy storage system (BESS) in a stand-alone microgrid. The stand-alone microgrid is composed of BESS, diesel generator and controllable loads, where all of them have a rated power of 50kW. The four cases are considered as following: 1) BESS with a stiff grid 2) BESS with the diesel generator 3) BESS with passive damping + diesel generator 4) BESS with active damping + diesel generator, and their stabilities are analyzed in the frequency domain and discrete time domain. The comparative analysis for four cases are verified through simulation and experiments through demonstration site of the stand-alone microgrid, where the DC link is connected to a 115kW battery bank composed of 48 lead-acid batteries (400AH/12V). Experimental results show a good agreement with the analysis.