• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2407-2417
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• 1993

Thermal deformations and stresses due to temperature changes are the serious problems in cryogenic structures such as the torque tube in a superconducting generator, In this paper, the equations of thermal expansion coefficients expressed only by material properties and winding angles are derived for the filament wound composite tubes. The experimental results of thermal contraction of CFRP tubes are compared with those from theoretical approach. Composite tubes with optimally regulated thermal expansion coefficient are designed on the basis of the study for the torque tube in the superconducting generator with temperature distributions varying from 300K to 4.2 K. The filament winding angle of composites resisting thermal stresses properly is sought by the finite element method using layered shell elements. The results show that the composite tubes designed for the requirements in cryogenic environments can effectively cope with the thermal stress problem.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.65-68
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• 1999

The major deisng parameters that are considered in this paper are: 1) EMF according to width of field coil. 2) EMF according to magnetic shield length. Because of superconducting generator (SG) is actually and air cored machine with its rotor iron and stator iron teeth having been removed. In this case, the desing of the SG must be based on the 3D analysis of the magnetic field. This study presents an effective armature winding type with 3D FEM(Finite Element Method), and compares analyzed and measured results.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.2
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• pp.142-148
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• 1990

This paper deals with the desing method of Superconducting AC Generator (SCG). The establishment of design principle and design procedure of SCG are included in this study. Electric characteristics of SCG, such as synchronous reactance and sub-sub-transient reactance, are specified first as constraints and the size of SCG is calculated. Synchronous reactance and sub-sub-transient reactance are important factors because they determine the steady state and transient characteristics of SCG, respectively. A 20KVA SCG with double-shielded single-rotor is chosen for the case study. The design procedure proposed in this papar will also be applicable to large scale generators.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.4
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• pp.321-326
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• 1998

Electrical breakdown characteristics of liquid nitrogen($LN_2$) taking into consideration for application of high $T_c$ superconductor is very important. Also $LN_2$ will be used as both coolant and insulator in superconducting generator. In this paper, we investigated ac breakdown characteristics of cryogenic nitrogen gas above a $LN_2$ for rod-to plane electrode configuration. As result the breakdown mechanism of $LN_2$is dependence on bubble effect. And breakdown voltage is a ratio on bubble s size but electrodes arrangement is to make no difference. The breakdown voltage decreases slightly with increasing flow velocity, it again decreases abruptly with increasing flow velocity. These results were interpreted as the within pressure of rod electrode and Maxwell force.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.103-105
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• 1998

This paper presents the compensated 2-D magnetic fields analysis of superconducting AC generator(SCG) by using efficient 2-D model. 3-D analysis is necessary for the accurate analysis because SCG has a large leakage flux owing to the air cored winding and end ring structure. However, in 3-D FEM, considering the movement of rotor is difficult, so efficient 2-D model which can compensate the leakage flux has been proposed and the movement of rotor is easily considered. The characteristics in transient state of SCG and the prime role of damper also have been evaluated.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1996.11a
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• pp.116-121
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• 1996

An image of future power system which has introduced superconducting generator, cable, transformer, fault current limiter, SMES and so on is presented. Conceptual designs of each SC machines and devices are carried out. The SC cable and SFCL utilize the high Tc superconductor(HTS) cooled by liquid $N_2$Other devices use low temperature superconducting cooled by He. The SC power system models are proposed detailedly. In viewpoint of the operation and control SC power system, The concrete design direction and effective role of each SC apparatus are investigated. In this paper, it is pointed that superconducting fault limiters(SFCLs) should play an important part of the quenching current level coordination to prevent the other SC devices from quenching. Finially, SFCL are also expected to he very effective to introduce flexibility of power system configuration and operation due to their possibility to enhance transient stability and reduce short circuit current.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.92-96
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• 2003

This paper deals with the characteristics of persistent current switch (rCS) system fer applied HTS magnet system. To apply the high-Tc superconductor in superconducting machine such as motror, generator, MAGLEV, MRI, and NMR, the study on high-Tc superconducting persistent current mode must be performed. In this experiment, the PCS system consists otd superconducting magnet, PCS and magnet power supply. The superconducting magnet was fabricated by connecting four double pancake coils (DPCs) in series. The PCS was inductive double pancake coil type and heated up by the SUS 303L tape heater. The optimal length of PCS was calculated and thermal quench state of PCS was simulated by using finite element method(FEM) and compared with experimental results. The optimal energy to normalize the PCS was calculated and introduced. Finally, the persistent current was observed with respect to various ramping up rate and magnitude of charging current.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.4
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• pp.343-347
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• 2019

When referring to weight, volume, and efficiency, a SuperConducting Synchronous Generator (SCSG) is definitely superior to conventional generators as a large-scale wind power generation system. The SCSG is connected to a full power converter that transmits the energy from the SCSG to the power grid. To reduce the current stress and system cost, the SCSG which has nine-phase armature windings with three converters is used. This paper deals with a comparative analysis of 10 MW superconducting wind power generators with three-phase and nine-phase armature windings. The stator windings of SCSGs are of various types. Using the finite element method, SCSGs are analyzed and compared in terms of the weight and volume of SCSGs, the total length of the superconducting wire, harmonics, torque performance, and efficiency. The analyzed results will be effectively utilized to design large-scale superconducting generators for wind power generation systems.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.9
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• pp.104-109
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• 1999

The flywheel energy storage system using superconducting magnetic bearings is a device to store electrical energy as rotatioal kinetic energy by motor and to convert it to electrical energy by generator when it is necessary. The rotordynamic analysis should be performed with an adequate analytical model and equations of motion to identify the stable driving condition and the dynamic behavior. The critical speed and the unbalance response of superconducting magnetic bearings-flywheel system are studied in this paper. The analytical results show that the system has one forward whirling mode and two backward whirling models below 500rpm. The maximum displacement 0.75mm is detected at the first forward mode (385rpm)through unbalance response analysis. The analytical results are compared with the experimental result by the spin-down test. The experimental result shows that the maximum displacement is 0.7mm at 370rpm.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.2
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• pp.93-101
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• 2000

This paper presents a novel method for the transient of eddy currents in the dampers of a super-conducting synchronous generator(SCG). The method proposes a 2-D corrected model which takes into account the influence of leakage fluxes of the field winding ends by increasing the effective air gap in order to consider the high precision of the analysis for the conventional 2-D model. The electromagnetic fields for the corrected model are analyzed by the time-stepping finite element method, thus the eddy currents in the dampers and electro-motive forces(EMF) in the stator windings are calculated. As the results, it is proved the presented method is comparatively accurate by comparing measured phase EMF values and the simulation ones, where about 6.4% error at the maximum value of EMF is occurred between them.