• Progress in Superconductivity and Cryogenics
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• v.6 no.3
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• pp.33-37
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• 2004

This paper presents the construction and test results of an HTS induction motor. End rings and short bars were made of HTS tapes, To increase the efficiency and starting torque, HTS tapes can be used as the rotor bars. Because large current is induced in the rotor circuit, HTS tapes quench and high starting torque can be obtained. As the speed of rotor builds up. HTS tapes which are used as short bars become superconducting state again. After the HTS tapes recover from quench, resistance of the rotor circuit is nearly zero. In that case, power loss in rotor circuit is eliminated. Stator of the conventional induction motor was used as the stator of the HTS motor. Rated capacity of the conventional motor was 0.75 kW. Performances of the HTS induction motor were compared with those of the conventional motor with same volume and specification. Test result showed that the speeds of the HTS induction motor were the same with synchronous speed up to 2.6 Nm and 1.788 rpm at 9.7 Nm. It guarantees the high efficiency of the HTS motor. Starting torque of the HTS motor was more than twice of the conventional motor.

• Journal of Energy Engineering
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• v.8 no.2
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• pp.203-212
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• 1999

The Republic of Korea is actively constructing and operating nuclear power plants and will maintain the nuclear energy program in spite of the current stagnation of nuclear industries in advanced countries. The significant role of Korea in the world economy is well recognized as Korea became a member of OECD. The Korean economy is rated as the eleventh largest in the world. Korea is a very important customer in the world nuclear market and is also regarded as a potential future supplier. However, the domestic and international environment for globalization of the Korean nuclear industry is not well established. This is mainly due to the past nuclear policy which has emphasized technological self-reliance with less attention to the international politics and trading. Under this background, this paper suggests the strategies for promoting the nuclear trade and expanding the influence in the decision making process of international nuclear community.

• Journal of Biosystems Engineering
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• v.35 no.1
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• pp.31-36
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• 2010

A small unmanned helicopter was suggested to replace the conventional spray system. Aerial application using an agricultural helicopter helps precise and timely spraying, and reduces labor intensity and environmental pollution. In this research, a rotor system (SW05) was developed and its lift capability was evaluated. Lift force for the dead weight of the helicopter was obtained at the grip pitch angle of $12^{\circ}$. As the pitch angle increased to $14^{\circ}$ and $16^{\circ}$, the payload increased to 176 N and 216 N, respectively. Compared with SW04 airfoil performance in the total lift, the SW05 airfoil showed nearly the same capacity, but the payload of the SW05 was reduced because of the increased dead weight. A rated flight condition was defined as lifting mean payload of 294 N with the grip pitch angles of $16{\sim}17^{\circ}$ at the rotor rotating speed of 850~950 rpm for the adjusted engine power. The fuel consumption would be 4.8~6.0 L/hr, and the air temperature of cooling fan should be kept below $160^{\circ}C$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1286-1291
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• 2018

In recent years, the proliferation of DER (distributed energy resources) is progressing rapidly. In particular, research on LVDC distribution grid with various advantages has begun. In order to commercialize this LVDC grid, direct current protection method should be established by analysis of DC faults. Recently, the development of HSCB (high-speed circuit breaker) for new ${\pm}750[V]$ LVDC grid has been researched. This paper deals with the calculation of the maximum short-circuit fault current of the HSCB as a part of the development of HSCB for the LVDC distribution grid. First, modeling using PSCAD was carried out for PV array with BESS on the Gochang Power Test Center system. Next, to calculate the rated capacity of HSCB, fault currents were calculated and the characteristics were analyzed through fault simulations. Thus, this study results can help to establish short-circuit capacity calculation of HSCB and protection plan for DC protection relay system.

• Journal of the Korean Society of Safety
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• v.22 no.5
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• pp.27-32
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• 2007

We investigated the damage of the TTL ICs which manufactured five different technologies by artificial microwave. The artificial microwave was rated at a microwave output from 0 to 1000W, at a frequency of 2.45GHz. The microwave power was extracted into a standard rectangular waveguide(WR-340) and TTL ICs were located into the waveguide. TTL ICs were damaged two types. One is breakdown which means no physical damage is done to the system and after a reset the system is going back into function. The other is destruction which means a physical damage of the system so that the system will not recover without a hardware repair. TTL SN74S08N and SN74ALS08N devices get a breakdown and destruction occurred but TTL SN74LS08N, SN74AS08N and 74F08N devices get a destruction occurred. Also destructed TTL ICs were removed their surface and a chip conditions were analyzed by SEM. The SEM analysis of the damaged devices showed onchipwire and bondwire destruction like melting due to thermal effect. The tested results expect to be applied to the fundamental data which interprets the combination mechanism of the semiconductors from artificial microwave environment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.10
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• pp.1846-1857
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• 2011

This paper deals with design and analysis of surface-mounted PM (SPM) motor for compressor of air-conditioning system for electric vehicle applications according to slot/pole combination. First, required torque-speed curve characteristics are determined from operating conditions of the compressor. Restricted conditions such as motor size limit and current density are also determined. And then, under same rated and restricted conditions, twelve models which have different slot/pole combinations each other are designed for various pole arc/pitch ratio using simple equations and 2-d finite element (FE) analyses. Designed models are analyzed and compared in terms of back-emf THD, cogging torque, torque ripple, power losses, efficiency, etc. On the basis of analysis results, it is found that the motor with a 6-pole PM rotor and a 27-slot stator has most outstanding performances in electromagnetic aspects. Finally, through the mechanical modal analysis and demagnetization analysis, it is concluded that the determined motor is most suitable for the compressor of air-conditioning system for electric vehicles.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.78-84
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• 2013

The objective of this paper is to develop 360 W class wind turbine tree using a helical type wind turbine. The performance of 100 W class helical wind turbine which finished the conceptual design has been forecast through the CFD analysis. After performed the analysis of one wind turbine performance, four wind turbine have been installed at the structure of a tree type and then the change of a output data has been verified through the CFD analysis. In this study, the CFD results of a helical wind turbine tree have been shown by a velocity and pressure distribution. The result could obtain more than rated power 360 W through the CFD analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.442-447
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• 2007

A very abnormal vibration was occurred at the LP(low pressure) turbine continuously during the pre-operation for a 550MW class USC(ultra super critical) steam turbine. This vibration was initiated at the rotating speed of about 3,450rpm and then the vibration amplitude was highly increased the number by $2{\sim}3$ times with the increase of the rotating speed to the rated speed(3,600rpm). In this paper, this abnormal vibration named spike vibration. This spike vibration was caused by the rubbing between the rotating bucket tip seal and the Lower Half of spill strip. Also, this paper presents the mechanism of the spike vibration and the proper method to eliminate this abnormal vibration problem. This result would be good practice to find the solution of similar high vibration in the USC steam turbines for power plant as well as industrial rotating machineries.

• Journal of Biosystems Engineering
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• v.37 no.3
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• pp.140-147
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• 2012

Purpose: This study was conducted to understand the work performance of crank-type rotavators and compare them with those of rotary-type rotavators in Korean farmland conditions. Methods: Tillage operations were carried out using both rotavators with the same nominal rotavating width and rated power. During the operations, PTO speed and torque, actual work speed, and rotavating width and depth were measured. To evaluate work performance, pulverizing ratio, inversion ratio, and specific volumetric tilled soil were calculated and compared for each rotavator. Results: It is found that the crank-type rotavator has better specific volumetric tilled soil performance and deep tillage, while the pulverizing ratio is worse. Conclusions: Crank-type and rotary type rotavator have diffenent properties each other in several work performances. It's important, therefore, to choose a suitable type of rotavator that satisfy the farmer's requirements in accordance with the condition of field and the purpose of tillage operation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.10
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• pp.59-66
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• 2011

In electric power system, the circuit breaker is not operated when the higher voltage then the rated TRV(transient Recovery Voltage) appeared in the circuit breaking, The TRV of a circuit breaker means the characteristics of reignition by the arc between two poles. and is decided by the value of connecting Impedance. In this paper we of carried out many kinds of experiments varying the types of bus, the types of installation, the length of installation between 22.9 [kV] level circuit breaker and MTR in general 154/22.9[kV] system, We also simulated the characteristics of TRV using EMTP-RV program. The suitability of TRV in assessed by Uc, RRRV(Rate of Rise of Recovery Voltage) which are defined by the international guide, IEC62271-100. The values of RRRV gained from the cable-made bus are 590[%] lesser than those from the NSPB-made bus respectively. So the triangled type is more rational in the aspect of TRV.