• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.8
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• pp.107-112
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• 2007

The flux-lock type SFCL consists of transformer with primary and secondary windings connected to a superconducting element in serial. It can be divided into the subtractive and the additive polarity windings according to the winding direction. It could change the fault current limiting characteristics according to the inductance ratio between the coil 1 and coil 2. We investigated the voltage-current characteristics of the flux-lock type SFCL according to the increment of applied voltage. When the applied voltage of the SFCL with the subtractive and the additive polarity windings was increased a initial limiting current ($I_{ini}$) and the quench time of the superconducting element were increased. The recovery time of the superconducting element was increased by increment of applied voltage. Therefore, it was confirmed that recovery characteristics in the flux-lock type SFCL were largely dependent on the consumed energy of a superconducting element because of increment of the consumption power into the superconducting element.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.89-98
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• 2010

Isolated boost converter is desirable in the dc/dc converter applications where isolation is required and extremely high step up is needed. Transformer used to step up low input voltage into high output voltage must satisfy the volt-sec balance condition. Conventional isolated boost converter is controlled with conducting intervals overlapping. In this case, there is a problem that control circuit is complicated. In this paper, it is proposed and analyzed the isolated boost converter which set up a reset winding for the volt-sec balance of transformer and can construct the control circuit simple by using a self-driven switch. Finally, the validity of the theoretical analyses for the proposed converter is verified by both simulations and experiments on the 10[W] class isolated boost converter.

• Journal of the Korean Society of Safety
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• v.33 no.3
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• pp.15-20
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• 2018

There have been a number of major fatal fire accidents in Korea recently. The number of fires in 2017 were 44,178, which is not only increasing number of fires but also increasing in casualties. Particularly, the fire at Jecheon Sports Center, which suffered many casualties, is expected to have a huge impact. The cause of the fire has not been determined yet, but heat waves on the ceiling have also been pointed out. As such, the copper heating waves, which are used as a preventive measure against damage of pipes due to freezing of pipes, etc., always have a fire hazard. To determine the possibility of a flame-resistant heated fire, a positive electric cable product was used to artificially ignite and analyze the results. In case of a short circuit, the external covering of the positive electric cable is damaged, but not short circuit unless the heating material surrounding the wire is damaged. Due to the characteristics of heating cable for preventing copper waves, the chances of insulation becoming more severe due to moisture and temperature changes are higher than normal wires. If the internal heating system is carbonized by insulating deterioration without damage to the outer coating, it is likely to cause trekking, to form a winding loop in the heating materials, and to cause short circuit in the heated materials. For the positive temperature line, if the middle is shorted, the current continues to flow to the short circuit unless the breaker disconnects. Consequently, a heated fire that does not cut off the power immediately may leave multiple marks or cuts.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.6
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• pp.536-543
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• 2004

Slotless Permanent Magnet Brushless DC Motor(PM BLDC) with the characteristics of high speed and power density has been more widely used In Industrial and factory machine. Generally, PM BLDC meter is necessary that the three Hall-lCs evenly be distributed around the stator circumference in case of the 3 phase motor. The Hall-ICs are set up in PM BLDC Motor to detect the main flux from the rotor. therefore the output signal from Hall-ICs is used to drive a power transistor to control the stator winding current. However, instead of using three Hall-ICs, if it used only one Hall-IC, we can estimate information of the others phase in sequence through a rotor This paper identified the characteristics and performance by using one Hall-IC with the 3-phase, 2-pole, 6-slot PM BLDC motor.

• KIEAE Journal
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• v.9 no.3
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• pp.61-68
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• 2009

Gwangju Metropolitan Government & Ministry of Environment have signed a model city in response to Climate Change agreement. The agreement calls for Gwangju to cut greenhouse gas emissions 10% below 2005 levels by 2015. Gwangju has seen this agreement as an opportunity to cut pollution and conserve the environment as well as to reinvigorate local economy. According to policy of Gwangju, Gwangju held design competition for Gwangju City Arboretum on march, 2009. The purpose of design competition was to give a wide publicity to Gwangju as Hub City of Asian Culture and construct carbon-neutral arboretum in accordance with the policy of 'Low-Carbon and Green Growth'. First of all, a design concept of arboretum is 'winding, round, overlay 'to reflect the landscape of Nam-do which is surrounded by mountains and river flows through the village. Second, the arboretum has five different places with these themes - Forest of Festivals, Health, Nature, Nostalgia, Education and Future. Each place has a symbolic theme park and different flow planning respectively. Third, the most critical point is that the arboretum is a carbon-neutral park. Gwangju arboretum will soon be developed in metropolitan sanitary landfill and constructed as the O2 arboretum based on low carbon strategy. Fourth, the O2 arboretum suggests specialized issue : 'Energy Saving', 'Recycling System', 'Green Network', 'Water System(rainwater maintenance and wetland development)'. Besides, main buildings(greenhouse, visitor center, Nam-do experience exhibition hall, and forest museum) is designed in consideration of harmony with topography character, surroundings. Also, planting will be a multilayer plant based on native landscape trees in consideration of function and the growth characteristics.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.6
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• pp.411-420
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• 2000

The energy storage systems are being widely researched for the high quality of the electric power. The FES(flywheel energy system) is especially, on the center of the research because it does not make any pollution and its life is long. The FES converts the electrical energy into the mechanical kinetic energy of the flywheel and reconverts the mechanical energy into the electrical energy. In order to store as much energy as possible, the flywheel is supposed to be rotated with very high speed. The motor/generator of the FES should be high efficient at high speed, and generate constant torque with respect to the rotation. In this paper, a motor/generator employing a Halbach array of permanent magnets is designed and constructed to meet the requirements, and its characteristics are examined. The magnetic field is analysed by using the magnetic surface charge method. The armature winding is designed for the harmonic components to be minimized by using the FFT. The sinusoidal current for the motor driving are generated by the hysteresis current controller. A sample superconducting flywheel energy storage system is constructed with a duralumin flywheel which has a maximum rotating speed of 40,000[rpm] and a stored energy of 240[Wh] and its validity is examined through the experiment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.184-185
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• 2006

The flux-lock type superconducting fault current limiter (SFCL) has the attractive characteristics that can adjust the current limiting level by the turns ratio between two coils. Since the recovery characteristics of a superconducting element m the flux-lock type SFCL were dependent on the turns ratio between two coils, the analysis for the recovery characteristics of this type SFCL together with the current limiting characteristic is necessary to apply it to power system. When the applied voltage and load impedance were same, the recovery time of the superconducting element was 0.32sec in case that the turn's ratio between the primary and secondary windings was 63:21. In the meantime, when the turn's ratio of secondary winding increased to 3 times, the recovery time became longer to 0.58sec.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.429-432
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• 2009

The deformation and burst pressure of composite motor case highly depends on fiber material properties. Therefore, measuring exact fiber material properties is a priority item to develop a advanced composite motor case. However, the fiber material properties in composite motor case is very sensitive on the various processing variables (equipment, operator and environmental condition etc..)and size effect, so the fiber material properties can't be measured exactly from the existing specimen test method. This paper suggests a newly developed test method, hoop ring test, that is capable of pressure testing with ring specimens extracted from real composite motor case. The results of hoop ring test showed excellent agreement with measured fiber material properties from hydro-burst test with full scale composite motor cases.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.4
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• pp.59-65
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• 2014

In this paper, in order to improve efficiency performance of power amplifiers, a mode changeable autotransformer is proposed. Efficiency performance at the low-power mode can be improved by adopting the mode changeable autotransformer. A dual-mode autotransfomrer CMOS power amplifier using a standard 0.18-${\mu}m$ CMOS process is designed in this work. Number of turns in a primary winding is re-configurated according to mode change between the high-power mode and the low-power mode. Thus, the efficiency performance of the power amplifier at each mode is optimized. EM and total circuit simulation results verify that low-power mode power added efficiency(PAE) at 24dBm output power is improved from 10.4% to 26.1% using the proposed multi-mode operation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.133-139
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• 2005

Resonant-Type Magnetometer(RM) using high permeability isotropic magnetic material is designed to implement Smart Digital Compass. Theoretically, the inductance L of a coil, winding on the magnetic core, is proportion to the change of permeability $\mu(H)$ and, the change values of L can be obtain as the change of frequency by simple Schmitt Trigger circuit. By the use of integrated circuit switch, the RM can be designed with simple circuit and it can provide overcoming the drift by temperature and the variation of operating points in $\mu(H)$ curve. The facts that Metglas 2705M is an optimum magnetic material and ship's permanent magnetism can be obtain from measured values of RM are also known in this study.