• Aerospace Engineering and Technology
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• v.8 no.2
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• pp.122-126
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• 2009

KSLV(Korea Space Launch Vehicle)-I is designed as a launch vehicle to enter a 100 kg-class satellite to the LEO(Low-Earth Orbit). Attitude angles of the upper-stage, including roll, pitch and yaw are controlled by cold gas thruster system using nitrogen gas. To verify the flow rate of the gas charging system and to prepare a nitrogen gas charging scenario, the development of a gas charging simulator for RCS(Reaction Control System) is required. This paper describes the orifice design, development, and test of the gas charging simulator for RCS of KSLV-I.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.652-654
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• 2015

Integrated switched reluctance motor drive as an electric vehicle battery charger is presented in this paper. The SRM, which is used as the traction power in the driving mode, is used in the charge circuit to improve the power factor of charging system. The charging circuit can share the power switches of the asymmetric converter and phase windings of SRM to charge the battery, and can reduce the size and cost of the system in the plug-in system. To keep the rotor at standstill, zero torque control method is proposed. Since the inductances of the SRM windings are not same at any stop position, the charger controller controls the reference current to satisfy the total charging current with PFC and zero torque condition. A novel cubic equation method is proposed as a current reference distributor of the charging controller. Simulations are performed by MATLAB software and results satisfy the Effectiveness of proposed battery charging system.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.2
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• pp.99-106
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• 2012

In this paper, 15[kW] AC regenerative system for battery charging and discharging test is proposed. The regenerative system is able to regenerate surplus energy to the grid in discharging mode, and the inverter of the system can be operated as a converter to compensate scarce energy in charging mode. In case of the conventional DC charging and discharging system, the regenerative energy is consumed by a resistor. However, as the proposed system regenerates the surplus energy to the grid through using DC-AC inverter, the energy saving effect can be achieved. In this paper, 15[kW] battery charging and discharging system is developed, and the validity of the system is verified through simulation and experimental results.

• Asian Journal of Atmospheric Environment
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• v.9 no.2
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• pp.137-145
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• 2015

This study focused on the measurement of the actual charging state of ambient aerosol particles, which is important for understanding the intricate process of adverse health effects caused by particulate matter (PM). The net electrostatic charging state of $PM_{2.5}$ collected on filter media was measured in this study. The Faraday cage method and surface potential measurements were used in this study. The results showed that the polarities of the net charging state measured using these two methods were in agreement for 42 out of 48 samples (87.5%), and 36 samples (75%) were negatively charged. The filters were not significantly charged by friction between the filters and air not containing PM. Charge addition to or leakage from the filters was not observed over a two-month storage period. Net charging state of $PM_{2.5}$ collected on the filters was concluded to be negative in most cases, based on data's support of the assumption that aerosol charging state is not altered by the process of PM collection using filter.

• Journal of Korean Society of Rural Planning
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• v.21 no.1
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• pp.19-28
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• 2015

As environmental concerns including climate change drive the strong regulations for car exhaust emissions, electric vehicles attract the public eye. The purpose of this study is to identify rural areas vulnerable for charging infrastructures based on the spatial distributions of the current gas stations and provide the target dissemination rates for promoting electric cars. In addition, we develop various scenarios for finding optimal way to expand the charging infrastructures through the administrative districts data including 11,677 gas stations, the number of whole national gas stations. Gas stations for charging infrastructures are randomly selected using the Monte Carlo Simulation (MCS) method. Evaluation criteria for vulnerability assessment include five considering the characteristic of rural areas. The optimal penetration rate is determined to 21% in rural areas considering dissemination efficiency. To reduce the vulnerability, the charging systems should be strategically installed in rural areas considering geographical characteristics and regional EV demands.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.5
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• pp.362-367
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• 2016

Recently, wireless charging systems have expanded their applications from household electrical appliances to outdoor activity devices. In wireless charging systems, solar cells have versatile advantages, such as abundant raw materials within the earth, reasonable prices of products, and highest power conversion efficiency. In this study, the photovoltaic effect between a silicon solar cell and a photon of infrared wavelength was simulated using a Shockley diode equation. A solar cell power charging system was then set up to: 1) clarify mechanisms of the charging interaction based on the photovoltaic effect with a laser source, and 2) verify interdependency of the parameters: laser settings and geometrical position between a solar cell and the laser. As was observed, the solar cell generates more power when the photon was irradiated uniformly, intensively, and vertically on the surface of the solar cell.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.2
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• pp.79-86
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• 2004

An analytical and experimental study has been conducted to determine the optimal charging mass of working fluid for the maximum heat transport capacity of heat pipe with axially grooved wick. When the heat pipe is operated in a steady state, the liquid-vapor meniscus recession of working fluid to the bottom of groove is occurred in the evaporator region. In this work, the optimal charging mass of working fluid was obtained by considering the meniscus recession from the axial variation of capillary pressure, the radius of curvature and wetting angle of meniscus of liquid-vapor interface. Experimental results were also obtained by varying the charging mass of working fluid within a heat pipe, and presented for the trend of maximum heat transport capacity corresponding to the operating temperature and the elevation of heat pipe. Finally, the analytical results of the optimal charging mass of working fluid were compared with those from the experiment, both of which were in good agreement with each other.

• Journal of Power Electronics
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• v.13 no.3
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• pp.329-338
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• 2013

In this paper, the charging characteristics of series resonant type high voltage capacitor chargers considering the transformer stray capacitance have been studied. The principles of operation for the four operational modes and the mode changes for the four different switching frequency sections are explained and analyzed in the range of switching frequency below the resonant frequency. It is confirmed that the average charging currents derived from the above analysis results have non-linear characteristics in each of the four modes. The resonant current, resonant voltage, charging current, and charging time of this capacitor charger as variations of the switching frequency, series parallel capacitance ratio ($k=C_p/C_s$), and output voltage are calculated. From the calculation results, the advantages and disadvantages arising from the parallel connection of this stray capacitance are described. Some methods to minimize charging time of this capacitor charger are suggested. In addition, the results of a comparative test using two transformers whose stray capacitances are different are described. A 1.8 kJ/s prototype capacitor charger is assembled with a TI28335 DSP controller and a 40 kJ, 7 kV capacitor. The analysis results are verified by the experiment.

• Journal of Information Processing Systems
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• v.16 no.3
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• pp.677-687
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• 2020

This paper deals with the electrical shock that can occur in a car wireless charging system. The recently released the Wireless Power Consortium (WPC) standard specifies that the receiver must be protected from the radio power generated by the transmitter and presents two scenarios in which the receiver may be subjected to electrical shock due to the wireless power generated by the transmitter. The WPC also provides a hardware approach for blocking the wireless power generated by the transmitter to protect the receiver in each situation. In addition, it presents the hardware constraints that must be applied to the transmitter and the parameters that must be constrained by the software. In this paper, we analyze the results of the electric shock in the vehicle using the WPC certified transmitter and receiver in the scenarios presented by WPC. As a result, we found that all the scenarios had electrical shocks on the receiver, which could have a significant impact on the receiver circuitry. Therefore, we propose wireless power transfer limit (WPTL) algorithm to protect receiver circuitry in various vehicle charging environments.

• Journal of Korean Society of Rural Planning
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• v.20 no.4
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• pp.137-143
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• 2014

Car exhaust emissions are recognized as one of the key sources for climate change and electric vehicles have no emissions from tailpipe. However, the limited charging infrastructures could restrict the propagation of electric vehicles. The purpose of this study is to find the vulnerable districts limited to the charging station services after meeting the goal of Ministry of Knowledge Economy(12%). We assumed that the charging service can be provided by current gas stations. The range of the vulnerable grades was determined by the accessibility to current gas stations and the vulnerable regions were classified considering the optimal number of charging stations estimated by the efficiency function. We used 4,827 sub-municipal divisions and 11,677 gas station locations for this analysis. The results show that most of mountain areas are vulnerable and the fringe areas of large cities generally get a good grade for the charging infrastructure. The gangwon-do, jeollanam-do, gyeongsangbuk-do, and chungcheongnam-do include more than 40% vulnerable districts.