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류경우,김해종 한국전기전자재료학회 1998 전기전자재료학회논문지 Vol.11 No.7
Recently a few MJ superconducting magnetic energy storage ($\mu$ SMES) devices become commerci-ally available as one of the energy storage devices for uniterruptible power supply (UPS) systems. For such a ($\mu$ SMES) devics, a few kA class superconducting cables with high current density, high stability and excellent pulse characteristics are required. To acquire data for the superconduction cables related to design and fabrication of a 0.7 MJ $\mu$ SMES device, we tested critical currents and quench characteristics for several winding tensions and various remping rates especially. It is shown from the results that winding tensions have much influence on quench currents of the $\mu$ SMES devices.
류경우,마용호,Ryu, Kyung-Woo,Ma, Yong-Ho 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.4
AC loss of a superconducting conductor has a strong influence on the economic viability of a superconducting fault current limiter, which offers an attractive means to limit short circuit current in power systems. Therefore, the AC loss characteristics in several fault current limiting elements of a coil type have been investigated experimentally. The test result shows that AC losses measured in the fault current limiting elements depend on arrangement of a voltage lead. The AC loss of a bifilar coil is smallest among the fault current limiting elements of the coil type. The measured AC loss of the bifilar coil is much smaller than that calculated from Norris's elliptical model. However, the loss measured in a meander, which is frequently used in a resistive fault current limiter, agrees well to the theoretical one.
자장방향이 적층 Bi-2223도체의 자화손실에 미치는 영향
류경우,김현준 한국전기전자재료학회 2003 전기전자재료학회논문지 Vol.16 No.1
The ac loss is an important issue in the design of high-Tc superconducting power devices such as transformers and cables. In these devices many Bi-2223 tapes are closely stacked together and exposed to alternating magnetic fields that can have different orientations with respect to a tape. In such arrangement the magnetization loss is influenced by the screening current induced in adjacent tapes and thus different from that in a single tape. This stacking effect was experimentally investigated by measuring the magnetization loss in a stack, which consists of a number of tapes. First the magnetization loss in the single tape was measured in order to confirm the reliability of the loss data measured in the stack. The results for the single tape coincide well will the loss characteristics described in other previous works. For the stack In parallel and longitudinal magnetic fields the measured loss is Independent of both the number of tapes and stacking type. The longitudinal magnetization loss Is well explained rather by the slab model for decoupled filaments. For the tall stack in perpendicular field the measured loss at low fields is greatly decreased, compared to the loss of the single tape. However the loss at high fields is unaffected. These loss behaviors in the tall stack are well described by the slab model for full coupling.
류경우,오세규 대한건축학회 2001 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.21 No.1
The purpose of this study is to investigate the use of pilots with regard to the plan type of elementary schools and its problems and to explore some improvement schemes. The subjects of this research include the elementary schools in Gwang-ju city which have been established since 1990 when the pilots was first introduced. An investigative post-occupancy evaluation of pilots was performed by employing a sample survey of 6 schools whose types were different from each other. Preliminary research was done on 37 schools. The sample survey compared and evaluated the integration and distribution of functions, the physical elements of plan types, connections with surrounding circumstances and the uses under each condition. This study found that the use of pilotis at elementary schools was inclined toward passage. Teachers usually use pilotis only for movement, while students use it in many ways according to the individual property. The frequency of use of the pilotis is high, but the recognition level and satisfaction level of the users were quite low. Accordingly, I suggest that the plan type of elementary schools give careful consideration to the quality and function of pilotis, so that it may be better used.
전류분포가 3본-도체의 임계전류/교류손실 특성에 미치는 영향
류경우,최병주 한국전기전자재료학회 2003 전기전자재료학회논문지 Vol.16 No.5
AC loss is an important issue in the design of high-T$\sub$c/ superconducting power cables which consist of a number of Bi-2223 tapes wound on a former. In the cables, the tapes have different critical currents intrinsically. And they are electrically connected to each other and current leads. These make loss measurements considerably complex, especially for short samples of laboratory size. So special cautions are required in the positioning of voltage leads for measuring the true loss voltage. In this work we have prepared a conductor composed of three Bi-2223 tapes with different critical currents. The critical current and AC loss characteristics in the conductor have experimentally investigated. The results show that for uniform current distributions the conductor's critical current is proportional to the critical current of the Bi-2223 tape to which a voltage lead is attached. However it depends on the current non-uniformity parameter in the conductor rather than the tape's critical currents for nonuniform current distributions. The loss tests indicate that the AC loss is dependent on arrangements of voltage leads but not on their contact positions. The measured losses in the conductor also agree well with the sum of the transport losses measured in each Bi-2223 tape.
인접 교류전류가 Bi-2223테이프의 통전손실에 미치는 영향
류경우,최병주 한국전기전자재료학회 2001 전기전자재료학회논문지 Vol.14 No.3
Bi-2223 tapes have been developed for low-field power applications at liquid nitrogen temperature. When the Bi-2223 tapes are used in an application such as a power transmission cable or a power transformer, they are supplied with an AC transport current simultaneously. AC loss taking into account such real applications is a crucial issue for power applications fo the Bi-2223 tapes to be feasible. In this paper, the transport losses for different AC current levels and arrangements of the neighboring tapes have been measured in a 1./5 m long Bi-2223 tape. The significant increase of the transport losses due to neighboring tape's AC currents is observed. An increase of the transport losses caused by a decrease of the Bi-2223 tape's critical current is a minor effect. The measured trasprot losses could not be explained by a dynamic resistance loss based on DC voltage-current characteristics in combination with the neighboring tape's AC currents.The trasport losses do not depend on the frequency of the neighboring tape's AC currents but is arrangements in the range of small current especially.
외부 교류자장이 Bi-2223테이프의 동저항 및 손실특성에 미치는 영향
류경우,최병주,Ryu, Kyung-Woo,Choi, Byoung-Ju 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.5
A Bi-2223 tape has been developed for power applications such as a fault current limiter, a power cable and a superconducting magnetic energy storage system. In such applications, the Bi-2223 tape carries time varying transport current and in addition experiences time varying external magnetic field. It is well known that the external magnetic field not only causes magnetization loss in the Bi-2223 tape, but also drastically increases transport loss due to a so-called 'dynamic resistance' We developed an evaluation setup, which can measure transport loss in external at magnetic fields. Using this equipment, we measured the dynamic resistances for various amplitudes and frequencies of an external at magnetic field perpendicular to the face in the tape. Simultaneously we investigated the effect of an external ac field on transport loss with different experimental conditions. This paper describes test results ana discussions on correlation between the dynamic resistance and the transport loss for the Bi-2223 tape.