• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.4
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• pp.329-335
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• 2003

This study is on a experiment which shows to defrost automatically on the optimum time regardless of defrosting method. The result shows that the more defrost layers increase in fin tubes of evaporation, the less the section of the circulating air reduce. Thickness of the frost formation increases, so a pressure difference of ventilation increase, as a result automatic defrosting system sets the time COP drops suddenly up optimum time. Automatical defrosting system can find out the initial related current of evaporator fan motor and the value of load current in the optimum time. And it sets defrosting time, evaporating temperature, and temperature in refrigerator up system requiring value. Consequence of this experiment is that energy consumption with defrost load gets effect of reduction of eleven percent per 25.4 hours compared with common defrosting.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.192-195
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• 2002

The thesis proposes the sensorless vector control method that estimates the rotor speed and rotor time constant at the same time using stator current. In the proposed method, stator current error in the stationary reference frame is proportional to estimated speed error, and stator current error in the synchronous reference frame is proportional to estimated rotor time constant error. The proposed method can simultaneously produce a fast speed estimation and rotor time constant estimation. Therefore, this new method offers an improvement in the performance of a sensorless vector controller. And, the superiority of the proposed method is verified by simulation.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.91-94
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• 2003

A DC railway system has low feeder voltage, The fault current can be smaller than the current of load starting. So it is important to discriminate between the small fault current and the load starting current. The load starting current increases step by step but the fault current increases all at once. So the type of ${\Delta}I$ relay(50F) was developed using the different characteristics between the load starting current and the fault current. As for the load starting current, the time constant of load current at each step is much smaller than that of the fault current. First, to detect faults in DC railway systems, an algorithm using the time constant calculated by the method of least squares is presented in this paper. Secondly, to compose a protection scheme for DC railway systems is presented in this paper.

• 전기의세계
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• v.26 no.6
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• pp.59-65
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• 1977

A study on the decreasing method of secondary arc current on single phase reclosing. One of the major problem in case of using the single phase reclosing scheme for long distance UHV transmission line is the time required to deionize secondary arc current. This paper descritbes the way of inducing the formular of secondary arc current originated at the times of opening and closing the ground interrupting switch. The result was investigated by the method of numerical analysis and proved that the secondary arc current was decreasing sufficiently. Application of this method proposed by the authod makes it possible to deduce the dead time and to improve success-rate of reclosing.

• Journal of Magnetics
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• v.12 no.4
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• pp.156-160
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• 2007

In this paper, we analyze the errors associated with magnetic field interference for fiber-optic current sensors working in a three-phase electric system and provide a solution to compensate the interference. For many practical conductor arrangements, the magnetic filed interference may cause errors unacceptable for the accuracy requirements of the sensors. We devised a real time compensation method for the interference by introducing geometric and weight factors. We realized the method using simple electronic circuits and obtained the real time compensated outputs with errors of ${\pm}1%$.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.219-223
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• 2000

In this paper a new current controller with dead time compensation for small time constant PMSM is proposed. Precise analysis on voltage distortion by dead time and device characteristics is presented. Simulation results are presented to demonstrated the validity of the proposed method.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.6 no.1
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• pp.10-19
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• 2020

Boron Neutron Capture Therapy (BNCT) has the advantage of selectively removing cancer cells ingesting boron compounds. In this study, the benefits for treatment time and boron compound injection dose were compared between current neutron sources and a high current neutron sources to be developed in near future. The time-activity curve (TAC) of GBM (Glioblastoma) for one bolus injection was obtained by applying modified 3 compartment model. The treatment time was determined for an accelerator-based neutron sources at the present time and a high current accelerator based neutron source to be developed in the near future. In the case of the double amount of IAEA-recommended neutron flux, the treatment time was shortened to 15 minutes. In the case of high current accelerators, which are five times the amount of IAEA-recommended neutron flux, the irradiation time is within 5 minutes. The use of a high current accelerator based neutron source in BNCT is advantageous in terms of treatment time. In addition, it can increase the efficiency of use of neutrons and reduce the boron compound injection dose to patients, thus reducing pharmacological toxicity.

• Journal of the Korean Society of Safety
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• v.38 no.4
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• pp.8-14
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• 2023

This study presents the characteristics of short circuits (SCs) caused by excessive currents in high-voltage cables used in electric vehicles and emphasizes the need to calculate the cross-sectional areas of these cables according to the SC current. Three direct current power supplies were connected in parallel to test the SC characteristics caused by excessive currents, and a timer and a magnetic contactor were used to deliver the conduction time and SC current. A circular infrared-radiation heater was used to test the temperature-dependent SC characteristics, a thermocouple was used to measure the temperature, and a shunt resistor was used to measure the current. As the SC current increased, the fusing time of the cable decreased. Additionally, a high-voltage cable (with an area of 16 mm² ) used in electric vehicles fused when a current (approximately equal to 55 times the allowable current) flowed for 0.2 s (operating time of the protective device). When the SC current is 10 kA, the cable may fuse during the operating time of the protective device, thus creating a fire hazard. In electric vehicles, the size of the SC current increases in proportion to the capacity of the battery. Thus, the cross-sectional areas of the cables used should be calculated accordingly, and cable operations should be properly coordinated with the surrounding protective devices.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.377-384
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• 2009

In this paper, leakage current sensing module of SoC(System on Chip)type and real time monitoring system under consideration of electromagnetic interface in power trunk line are developed. The first, leakage current sensing module of SoC type under consideration of electromagnetic interface is developed, and the developed sensing module of SoC type is composed of leakage sensing part, power supply part, interface part, communication part, AD(Alternating current to Direct current)convert part and amplification part. And also the electromagnetic compatibility is evaluated by conduction and radiation of EMI(Electromagnetic Interference) for developed sensing module. The developed system can have confidence, stability and do energy saving under mixed electric circumstance of the low voltage communication device and high voltage equipment. The second, the real time remote monitoring system is developed using designed wire and wireless communication module with leakage current sensing module of SoC type. The developed real time remote monitoring system can monitor sensing state, occurrence state of leakage current and alarm for each step etc.. And the device configuration, PCB layout for leakage current sensing module of system on chip type and the experiment configuration in consideration of EMI are presented. Also the measurement results of conduction and radiation for EMI are presented.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.48-48
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• 2009

Conventionally in pulsed gas metal arc welding (GMAW-P), drop transfer is analyzed with simplest square pulse waveform. While the pulse current is described by four parameters (peak current magnitude and time plus base current magnitude and time), it deviates the real pulse shape. Real pulse can be better idealized by the trapezoidal pulse waveform described by two additional parameters, i.e., current rise and fall rate (dI/dt). Power source response rate is described by these parameters. In this work, the effect of these parameters on drop transfer is predicted by the force displacement model (FDM). While peak current has significant effects on drop detachment, drop transfer is also influenced by the current rise rate. Predictions indicate that the current rise rate can have considerable effects on the size of the detached drop if other pulse parameters are kept constant. FDM is applied to determine peak time for one drop one pulse condition (ODOP) when rests of the pulse parameters are given. The predicted range of ODOP shows good agreement with experimental data.