• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.190-192
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• 1996

This paper is a study on the rotating type of superconducting power supply(R.S.P.S.) with superconducting excitation coils. In this paper, a new idea of excitation coil is introduced to control the pole-flux in air gap. We manufactured the R.S.P.S. by using superconducting excitation coils and measured the charging current of superconducting load with respect to rotational speeds and excitational current. Through this experiment, 425A of maximum current was obtained a few minutes. It turned out that the charging rate of load current is proportional to rotational speeds and excitational current. Furthermore, it is found that it's possible to generate the charge current of thousands of amperes by using wires of larger critical current.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.438-441
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• 1999

One of the most important aspect in developing High-Tc Superconducting Synchronous Motor is producing high-Tc superconducting tapes that withstand the amount of currents that is needed to run the motor with stability. The purpose of this paper is to find the magnetic field distribution inside the motor in order to find out if the high-Tc superconducting tapes operate stably in actual motor operation. With this goal, magnetic field distribution in a detailed model of the actual motor was analyzed through F.E.M. By analyzing the field distribution acquired through the computer simulation, it has been observed whether the high-Tc superconducting tape maintains its superconductivity in actual motor operation. Also, the effects of the flux damper on the motor's operational characteristics and the magnetic field distribution have been analyzed. As a result, it has been proved that the high-Tc superconducting tapes can withstand 600 A turns which is required by the previous simulation aimed at developing this motor. It has also seen that the flux damper reduces armature reactance during the motor operation and change of load, helping the stable motor operation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.12
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• pp.1000-1003
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• 2012

The superconducting fault current limiter (SFCL) can quickly limit the fault current shortly after the short circuit occurs and recover the superconducting state after the fault removes and plays a role in compensating the voltage sag of the sound feeder adjacent to the fault feeder as well as the fault current limiting operation of the fault feeder. Especially, the flux-lock type SFCL with an isolated transformer, which consists of two parallel connected coils on an iron core and the isolated transformer connected in series with one of two coils, has different voltage sag compensating and current limiting characteristics due to the winding direction and the inductance ratio of two coils. The current limiting and the voltage sag compensating characteristics of a SFCL using a transformer winding were analyzed. Through the analysis on the short-circuit tests results considering the winding direction of two coils, the SFCL designed with the additive polarity winding has shown the higher limited fault current than the SFCL designed with the subtractive polarity winding. It could be confirmed that the higher fault current limitation of the SFCL could be contributed to the higher load voltage sag compensation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.8
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• pp.1164-1169
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• 2014

Recently, an interest in a hybrid system combining only the merits of the conventional wheel-rail system and Maglev propulsion system is growing as an alternative to high-speed maglev train. This hybrid-type system is based on wheel-rail method, but it enables to overcome the speed limitation by adhesion because it is operated by a non-contact method using a linear motor as a propulsion system and reduce the overall construction costs by its compatibility with the conventional railway systems. Therefore, the design and characteristic analysis of a coreless-type superconducting Linear Synchronous Motor (LSM) for 600km/h very high speed railway system are conducted in this paper. The designed coreless-type superconducting LSMs are the distributed winding model, the concentrated 1 layer winding model and the concentrated 2 layer winding model, respectively. In addition, the characteristic comparison studies on each LSM are conducted.

• Progress in Superconductivity and Cryogenics
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• v.7 no.1
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• pp.42-46
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• 2005

The resistive type high temperature superconducting fault current limiter (HTSFCL) limits the fault current using the resistance generated by fault current. The generated resistance by fault current makes large pulse power which makes the operation of HTSFCL unstable. So, the cryogenic cooling system of the resistive type HTSFCL must diffuse and eliminate the pulse energy very quickly. Although the best way is to make wide direct contact area between HTS winding and coolant as much as possible, HTS winding also needs the impregnation layer which fixes and protects it from electromagnetic force. This paper deals with the thermal conductivity and dielectric strength of some epoxy compounds for the impregnation of high temperature superconducting (HTS) winding in liquid nitrogen. The measured data can be used in the optimal design of impregnation for HTS winding. Aluminar filling increased the thermal conductivity of epoxy compounds. Hardener also affected the thermal and electric characteristic of epoxy compounds.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.8
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• pp.418-423
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• 2000

In this paper, we reported the current limiting properties of superconducting fault current limiters (SFCL). Our SFCL was patterned in a coil-type on a YBCO film deposited using rf sputtering techniques and was coated with a gold shunt layer in order to disperse the heat generated at hot spots in the YBCO film. Current increased up to 13.5 Apeak at 60 Hz for the voltage of 11.5 Vpeak, which is the minimum quench point, and increased up to 17.6 Apeak at 60 Hz for the voltage of 80 Vpeak. The quench completion time was 5 msec at 11.5 Vpeak and 4 msec at 80 Vpeak respectively. We think that this architecture using coil-type SFCL can be useful for the protection of the power delivery systems from fault currents.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.465-470
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• 2011

Recently fault currents are increasing in a network. It is caused by increase in electric demand and high penetration of distributed generation with renewable energy sources. Moreover, distribution network has become more and more complex as mesh network to improve the distribution system reliability and increase the flexibility and agility of network operation. Accordingly, the fault current will exceed capacity of circuit breakers soon and all the various rational solutions to solve this problem are taken into account. Under these circumstances, superconducting fault current limiter(SFCL) is a new alternative in the viewpoint of technical and economic aspects. This study presents operation processes for a resistive-type of SFCL, and it proposes reliability model for the SFCL. When a SFCL is installed into a network, the contribution of decreased fault currents to failure for distribution equipments can be quantified. As a result, it is expected that a SFCL makes the reliability of adjacent equipments on existing network improve and these changes are analyzed. We propose a methodology to evaluate the reliability in the distribution network where a SFCL is installed considering a reliability model for resistive-type of SFCL and reliability changes for adjacent equipments which are proposed in this paper.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.547-550
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• 2004

Superconducting fault current limiter(SFCL) is expected to be introduced into electric power system in future as an effective countermeasure for the increase of the short-circuit current due to the growth of the electric power system. SFCL has a merit that the fault current can be limited by the resistance generated when a superconductor transits from a superconducting state to a normal state without additional detecting device. In this paper, we investigated the resistance variance of resistive type SFCL and the fault current limiting characteristics due to the amplitude of source voltage. We could obtain the more effective fault current limiting characteristics of SFCL as the source voltage increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.523-526
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• 2004

According to the continuous demand for power and the growth of electric power utilities, the electric power transmission capacity was increased. The increase of the electric power transmission capacity results in an increase of the fault current level a fault happened. So the superconducting fault current limiter(SFCL) has been reached as the countermeasure for the reduction of the fault current. In this paper, we investigate the fault currents characteristics of resistive type SFCL according to fault angles when AC power source applied. As the fault angles increase, the first peak value of fault current decreased lower. On the other hand, the power burden of SFCL increased.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.55-59
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• 2018

Currently, the development of industry makes needs larger electric supply. Providers must consider the efficiency about losses and reliability of the system. In this case, DC power system can save electrical energy; long-distance transmission line losses. Relevance to switch technology with a voltage-source converter (VSC) in AC-DC conversion system have been researched. But, protection device of DC-link against fault current is still needed to study much. VSC DC power system is vulnerable to DC-cable short-circuit and ground faults, because DC-link has a huge size of capacitor filter which releases extremely large current during DC faults. Furthermore, DC has a fatal flaw that current zero crossing is nonexistence. To interrupt the DC, several methods which make a zero crossing is used; parallel connecting self-excited series LC circuit with main switch, LC circuit with power electronic device called hybrid DC circuit breaker. Meanwhile, self-excited oscillator needs a huge size capacitor that produces big oscillation current which makes zero crossing. This capacitor has a quite effective on the price of DCCB. In this paper, hybrid self-excited type superconducting DCCB which are using AC circuit breaker system is studied by simulation tool PSCAD/EMTDC.