• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.69-72
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• 1991

The propulsion of a ship is generally generated by the propeller motion. When we consider the importance of the acoustic noise of a ship, the epochal noiseless magnetohydrodynamic(MHD) propulsion system is studying now because the noise reduction of propeller has it's own limitation. This paper describes the characteristic analysis, theoretical analysis and efficiency versus thrust characteristics of MHD prolulsion system. When we generate 1 Tesla using normal conductor magnet, the efficiency is lower than 10 percent. It is essential to use superconducting magnet in order to increase the useful efficiency up to 50%. The validity of MHD propulsion system can be confirmed by analyzing other countries model test result.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.822_823
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• 2009

Superconducting fault current limiters (SFCLs) provide one of the most effective solutions to cope with enormous increase of fault current level. The 13.2 kV/ 630 A class resistive SFCL using coated conductor (CC) was developed and its short-circuit test was successful. Successful commercialization of the SFCL requires that no loss is produced by impedance of limiting coil during normal operation. Since the limiting coil consists of inner layer and outer layer, gap length between the layers is an important parameter to analyze the electromagnetic characteristics of coil. This paper deals with the electromagnetic characteristics of coil according to gap length through the simulation and analysis in comparison with experiment results.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.198-201
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• 1999

An optimal cooling method for HTS(high Tc superconductor) current leads has been analytically sought to minimize the required refrigerator power. The binary current lead is a series combination of a normal metal conductor at the warmer part and an HTS at the colder part. The lead is cooled by direct contacts with a two-stage cryocooler at the joint and at the cold end. It is clearly proven that there exists unique optimal values for the joint temperature and the current density to minimize the refrigerator power per unit current. the actual power input to the cryocooler in the optimal conditions is compared with its thermodynamic limit, and some significant issues in practical design are presented with a useful graphical method.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.53-56
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• 2001

The stability of PF 6-7 has been studied according to the transient analysis code TOKSCPF and quench analysis code QSAIT. We compare the stability and temperature rise with various Cu/SC ratios of 2.8 and 3.5 under the KSTAR normal operating conditions. It shows that the Cu/SC ratio has an influence on the quench propagation and stability margin. In transient operating condition, the Cu/SC ratio weakly influences on the temperature rise in PF magnet.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.97-100
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• 1999

Nowadays the high-Tc Superconducting Fault current Limiter (SFCL) is one of the superconducting devices which are very closed to commercialization. The most popular model of High-Tc SFCL is a magnetic shielding type. A superconductor of magnetic shielding type SFCL can be stable in the superconducting state, because there is no contact between the superconductor and the normal conductor. But this model needs large place to set up and in a fault condition, mechanical vibrations may happen to damage the superconductor or total device. In this paper, to solve these problems, the simplified model of magnetic shielding type SFCL was introduced.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.43-43
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• 2010

HTS(High Temperature Superconductor) cable has a high possibility of practical use due to the possibility of low voltage and high capacity transmission caused by its lower power loss than copper cable. On the other hand, when fault current occurred, resistance increase caused by superconductivity loss, the amount of power supplies has diminished, furthermore, it's necessary to take the possible danger of damage to HITS cable into account. Therefore, an effective plan for dealing with the above problem is to link HITS cable to SFCL. In this study, we researched the possibilities of normal transport current as well as the safety of HITS cable by analyzing the properties of transport current in HITS cable connected with SFCL.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.132-135
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• 2000

Magneto-resistances of the YBa$_2$Cu$_3$O$_{7-{\delta}}$ based coated conductors fabricated on the tilted single crystalline Ni substrates and RABiTS (rolling assisted bi-axially textured substrate) were measured under various magnetic fields. The activation energies of vortices were estimated from them by fitting equation of p = p$_o$ exp(-U(H,T)/k$_B$T). When currents flew in the rolling direction for the case of the tilted single crystalline YBCO on the RATS, the activation energies were similar to those of c-axis normal YBCO films on the SrTiO$_3$ single crystal substrates [5] and were slightly larger than those of the RABiTS coated conductors. On the contrary, for the currents flowing in the transverse direction, the magnetoresistances show double transitions in the temperature with much smaller activation energies.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.4
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• pp.172-177
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• 2006

During normal machine operation, partial discharge(PD) tests were performed with partial discharge analyzer(PDA) in two hydrogenerators. Six cable couplers were installed in circuit ring bus and endwinding of three phases. PDA showed that the normalized quantity number(NQN) and the partial discharge magnitude$(Q_m)$ were very low in hydrogenerator #1 and #2, respectively. The trend analyses of NQN and $Q_m$ value are available for monitoring of the insulation condition in hydrogenerator stator windings. The insulation condition of stator winding can be assessed. Discharge at conductor surface was discovered in B phase(C2 coupler) of hydrogenerator #1. Internal discharges were generated in A and C phases(C2 coupler) of hydrogenerator #1 and in A, Band C phases(C1 and C2 couplers) of hydrogenerator #2. Slot discharges occurred in A, Band C phases(C1 coupler) of hydrogenerator #1. The stator windings of two hydrogenerators were in good condition.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.276-279
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• 2003

The superconducting synchronous machine(S.S.M) including generator and motor has different electromagnetic structure from the conventional machine. With the help of superconductor having much higher operating current density than normal conductor, S.S.M can eliminate most of iron core filling inside of the conventional machine. This air-cored structure could be analysed and designed theoretically based on 2-dimensional(2-D) magnetic field distribution assuming that the windings are extended infinitely toward the axial direction. However the actual structure of S.S.M has the end regions interconnecting the straight parts of the same cross-section with the 2-D model. Therefore, this actual 3-D model has smaller field distribution than the 2-D model. In this paper, we consider the effect of the end regions on the output of a HTS model motor and suggest more accurate design approach through comparison of 2-D and 3-D magnetic field analysis.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2175-2178
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• 2005

During normal machine operation, partial discharge(PD) measurements were performed with turbine generator analyzer(TGA) in five high voltage motors(rated 6.6kV). These high voltage motors were installed with 80pF capacitive couplers at the terminal box. The PD patterns were displayed two dimensional and three dimensional. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). Off-line PD measurements were conducted on five motors. These motors were energized to 3.81kV. The PD levels in pC were measured with a conventional digital PD detector. The comparison of positive to negative PD indicates whether the defect elements of PD are within the insulation or on the insulation surface. Internal discharges were generated in phase A, B and C of COP-B and pulv.-B, in phase B of Pulv. C and in phase C of Pulv.-D motor. Discharge at conductor surface was discovered in phase A of Pulv. D motor. Slot discharges occurred in three phases of Pulv. E motor.