• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.3
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• pp.181-187
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• 2020

In this study, we propose a spherical flux concentration structure for omnidirectional wireless power transfer. Omnidirectional wireless power transfer technology is a method that can transmit power to a transmitter located in an arbitrary position in a two-dimensional or three-dimensional space. However, to improve the power transfer distance in a wireless power transfer system, the diameter of the coil or the number of windings must increase, thereby increasing the size of the transmitter. The proposed transmitter structure adds a ferrite core inside the transmitter coil so that the magnetic flux generated by the transmitter is directed toward the position of the receiver. As a result, the flux linkage and the mutual inductance increase. By implementing the omnidirectional wireless power transfer system using the proposed structure, the power transfer distance can be improved by 65% compared with the conventional system without increasing the size of the transmitter. Simulation shows that the proposed spherical flux concentration structure increases the mutual inductance of the omnidirectional wireless power transmission system.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.64-69
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• 2013

For power system protection, the distance relay settings are important. Apparent factor is a necessary parameter in distance relay settings. Apparent factors have to be calculated when setting the distance relays and doing the resetting in case of configuration change in power system. The problem is that the current method to calculate apparent factor requires tools and plenty of time to do fault analysis and this method is complex especially in case of configuration change. Therefore this paper proposes a fast algorithm to calculate apparent factor without the fault analysis. Test results prove that this algorithm is simple and accurate by simulation.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.10
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• pp.593-601
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• 2003

Distance realy is tripped by the line impedance calculated at the relay point. Accordingly the accurate operation depends on the precise calculation of line impedance. Impedance can be accurately calculated in case of overhead line. However, in case of power cables or combined transmission lines, impedance can not be accurately calculated because cable systems have the sheath, grounding resistance, and sheath voltage limiters(SVLs). There are also several grounding systems in cable systems. Therefore, if there is a fault in cable systems, these terms will severely be caused much error to calculation of impedance. Accordingly the proper compensation should be developed for the correct operation of the distance relay. This paper presents the distance calculating algorithm in combined transmission line with power cable using wavelet transform. In order to achieve such purpose, judgement method to discriminate the fault section in both sections was proposed using D1 coefficient summation in db4. And also, error compensation value was proposed for correct calculation of impedance in power cables section.

• Current Optics and Photonics
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• v.4 no.6
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• pp.571-575
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• 2020

Optical wireless power transmission (OWPT) is a good candidate for long-distance underwater wireless power transmission. In this work we investigate the transmission efficiency of underwater OWPT, depending on the operating wavelength. We consider four operating wavelengths: infrared, red, green, and blue. We also consider the cases of pure water and sea water for the working conditions. Our results show that it is necessary to select the operating wavelength of underwater OWPT according to the transmission distance and water type of the target application.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.3
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• pp.261-265
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• 2023

In this paper, we analyzed the transformation of the power following by the angle of incidence of the solar, the angle of photovoltaic module and artificial solar changed from 30° to 90° and synchronously changed the distance from 0.1 m to 0.5 m. Setting the distance between the artificial solar and the luminometer from 0.1 m to 0.5 m and set the angles to 90°, 60°, 45°, and 30°, the angle was 90° and when the distance was 0.1 m, the maximum Illuminance was 19,580 lux, the light could be obtained more. If the angle of incidence between the Artificial solar and the photovoltaic module was 90° and the variable resistance was 1,000 Ω at a distance of 0.4 m, the maximum power reached 0.82 W. Provided that the angle of incidence between the artificial solar and the photovoltaic module was 90° and the distance was 0.2 m since the variable resistance had the maximum power of 500 Ω, the maximum power was 0.78 W. At 1,000 Ω, the maximum power is 0.80 W so the maximum power at the variable resistance 1,000 Ω could obtain higher power than the variable resistance 500 Ω. The variable resistance was 1,000 Ω and the angle of incidence between the Artificial solar and the photovoltaic module was 90° at a distance of 0.4 m, and the maximum power reached 0.82 W. The angle was 60° at 0.3 m and 0.4 m the maximum power reached 0.10 W. The angle was 45° at 0.2 m maximum power reached 0.020 W, the angle was 30° at 0.4 m, and the maximum power reached 0.004 W. In four results about maximum power depending on the angle of incidence between the artificial solar and the photovoltaic module, the luminous efficiency and maximum power can be got the best at an angle of 90°.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.6
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• pp.562-568
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• 2013

This paper presents a design of a wireless power transfer system based on magnetic resonant coupling technology with in-band wireless communication. To increase the transmission distance and compensate for the change in the effective capacitance due to the varying distance, the proposed system used a loop antenna with a selectable capacitor array. Because the increased transmission distance enables multiple charging, we added a communication protocol operated at the same frequency band to manage a network and control power circuits. In order to achieve the efficient bandwidth in both power transfer mode and communication mode, the S-parameters of the loop antennas are adjusted by switching a series resistor. Our test results showed that the loop antenna achieved a high Q factor in power transfer mode and enough passband in communication mode.

• Progress in Superconductivity and Cryogenics
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• v.17 no.1
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• pp.40-43
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• 2015

Wireless power transfer technology is using the magnetic resonance recently drawing increased attention. It uses the resonance between transmitter and receiver coils to transfer power. Thus, it can improve the transfer distance and efficiency compared with the existing magnetic induction technique. The authors found from the previous study that the application of the superconductor coil to the magnetic resonance wireless power transfer system improved its efficiency. Its application to real life, however, requires the additional study on the effects of adjacent materials. In this study, the two resonance coils made by superconductor coils were used to aluminum and plastic shielding materials was placed between the coils. S-parameters were analyzed according to the position of the shielding material between the transmitter and receiver coils. As a result, the plastic of shielding material had no effect, but the aluminum of shielding material affected the wireless power transfer due to the shielding effectiveness.

• Progress in Superconductivity and Cryogenics
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• v.17 no.1
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• pp.36-39
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• 2015

Many studies are being conducted to implement wireless charging, for example, for cellular phones or electronic tooth brushes, via wireless power transmission technique. However, the magnetic induction method had a very short transmission distance. To solve this problem, the team of Professor Marin Soljacic proposed a magnetic resonance system that used two resonance coils with the same resonance frequency. It had an approximately 40% efficiency at a 2m distance. The system improved the low efficiency and short distance problems of the existing systems. So it could also widen the application range of wireless power transmission. Many studies on the subject are underway. In this paper, the superconductor coil was used to improve the efficiency of magnetic resonance wireless power transmission. The resonance wireless power transmission system had a source coil, a load coil, and resonance coils (a transmitter and a receiver). The efficiency and distance depended on the characteristics of the transmitter and receiver coils that had the same resonance frequency. Therefore, two resonance coils were fabricated by superconductors. The current density of the superconductor was higher than that of the normal conductor coil. Accordingly, it had a high quality-factor and improved efficiency.

• Journal of Radiation Protection and Research
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• v.41 no.4
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• pp.402-408
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• 2016

Background: Ascertainment bias are common in epidemiologic studies to assess the association between thyroid cancer risk and living near nuclear power plants because many thyroid cancers are diagnosed by chance through health examination. We surveyed the ultra sonography (USG) examination history and conducted thyroid and breast USG in residents living near nuclear power plants. Materials and Methods: The study population comprised 2,421 residents living near nuclear power plants in Korea. Information on demographic characteristics, including diagnostic examination history, was collected by interview using questionnaires. USG examination was conducted to evaluate the presence of thyroid nodules and breast lesion. Study participants were divided into 3 groups according to the distance of their respective villages from a nuclear power plant. The proportions of USG examination history and prevalence of thyroid nodules and breast lesions were compared between groups. Results and Discussion: Examination histories of thyroid USG were 23.1%, 13.7%, and 10.5% in men and 31.3%, 26.7%, 18.3% in women in the short, intermediate, and long distance groups, respectively. There were significant inverse associations between thyroid USG history and the distance from nuclear power plants (P for trend = 0.001 for men and 0.017 for women). However, there was no association between the distance of villages from nuclear power plants and prevalence of thyroid nodules. Conclusion: Our results suggest that there may be an ascertainment bias in population-based studies examining the harmful effects of NPPs examination and researchers should pay attention to ascertainment bias resulted from differential health examination. Correction for ascertainment bias, active follow-up and examination for all study population to remove differential health examination is needed.

• Journal of the Korean Society of Physical Medicine
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• v.16 no.1
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• pp.33-39
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• 2021

PURPOSE: This study compared the body composition according to the sport of short-distance and middle & long-distance athletes to identify the factors that affect the body composition. METHODS: Forty-eight athletes selected as youth national athletes in 2019 participated in the study. The study participants measured the length of the lower extremities, body composition, and anaerobic ability. An independent sample t-test was conducted to compare the body composition according to the event. In addition, the Pearson correlation was performed to identify the factors that influence the body composition. RESULTS: The leg length of the Short and Middle & long-distance athletes were similar (p = .584). On the other hand, there were differences in the body fat percentage (p = .001), lean percentage (p = .001), and BMI (p = .001). In addition, the body fat percentage was correlated with the lean body mass (r = .419) and BMI (r = .447). Furthermore, the lean body mass was correlated with the BMI (r = .849) and the peak power (r = .662) and mean power (r = .686) of the anaerobic capacity. Moreover, the BMI was correlated with the peak power (r = .490) and mean power (r = .543) of the anaerobic capacity. The peak power of the anaerobic ability was correlated with the mean power (r = .931). CONCLUSION: The body composition differed according to the sport. The body fat percentage correlated with the lean body mass and the BMI. The lean body mass correlated with the BMI, peak power of anaerobic ability, and mean power. The BMI correlated with the anaerobic capacity.