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Sangyeop Kwak,
Seyeon Lee,
Sangyeop Lee,
Woo-Seok Kim,
Ji-Kwang Lee,
Chan Park,
Joonhan Bae,
Jung-Bin Song,
Haigun Lee,
Kyeongdal Choi,
Kichul Seong,
Hyunkyo Jung, Song-yop Hahn
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ABSTRACT: A 600 kJ HTS SMES system has been developed for power system stabilization as a national project in Korea. Successful operating tests of the 600 kJ were recently completed. In this paper, a 2.5 MJ class SMES with HTS magnets of single solenoid, multiple solenoid and modular toroid type were optimized using a recently developed multi-modal optimization technique named multi-grouped particle swarm optimization (MGPSO). The objective of the optimization was to minimize the total length of HTS superconductor wires satisfying some equality and inequality constraints. The stored energy and constraints were calculated using 3-D magnetic field analysis techniques and an automatic tetrahedral mesh generator. Optimized results were verified by 3D finite element method (FEM).
IEEE Transactions on Appiled Superconductivity 07/2009; · 1.04 Impact Factor
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ABSTRACT: A 600 kJ superconducting magnetic energy storage system (SMES) project with high temperature superconductor (HTS) started as a national project in Korea. The HTS model coils were designed and fabricated for a preliminary test prior to the creation of a full scale prototype. Single reinforced BSCCO-2223 wires were used for the model coils and the operating temperature was decided to be 20 K. Even though an SMES is not an AC-powered device, time-varying currents during the charging and discharging periods lead to the generation of time-variation magnetic fields applied to the model coils and the generation of AC loss. In this paper, AC loss and the temperature distribution of model coils are analyzed and discussed.
IEEE Transactions on Appiled Superconductivity 07/2007; · 1.04 Impact Factor
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Myung-Jin Park,
Sang-Yeop Kwak,
Woo-Seok Kim,
Seung-Wook Lee,
Seung-Yong Hahn,
Ji-Kwang Lee,
Jin-Ho Han,
Kyeong-Dal Choi,
Hyun-Kyo Jung,
Ki-Chul Seong, Song-yop Hahn
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ABSTRACT: Auto tuning niching genetic algorithm was used to design optimal HTS magnets for the 600 kJ class SMES system under several design constraint conditions. Constraint conditions were operation loss of magnet (less than 2 W), inductance of magnet (less than 24 H), the number of double pancake coils (about 10 DPCs), the number of turns of DPC (less than 300 turns), outer diameter of DPC (close to 800 mm) and total length of HTS wire in a DPC (less than 500 m). As a result of optimum design, we obtained design parameters for the 600 kJ SMES magnet according to two operating currents, 360 A and 370 A. However, even though the HTS magnet was designed optimally in respect to the electromagnetics, consideration of mechanical integrity due to the stress by Lorentz force must not be neglected for the stable operation of the SMES system. Therefore, we developed a program, through the finite element method (FEM), for stress analysis due to Lorentz force in operation of the SMES system. In this paper, the stresses (radial and hoop stress) imposed on the designed HTS magnets were calculated by the program, and the results of stress analysis were discussed.
IEEE Transactions on Appiled Superconductivity 07/2007; · 1.04 Impact Factor
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ABSTRACT: AC loss is one of the important parameters in HTS (High Temperature Superconducting) AC devices. Among the HTS AC power devices, the transformer is an essential part in electrical power system. But, AC loss is one of the most serious problems of the HTS transformer, especially with pancake windings, because high alternating magnetic field is applied perpendicularly to the surface of BSCCO wire in HTS windings of that, comparing with the other HTS AC power devices. For the reason above the calculation of AC loss generated in the HTS windings should be carried out in advance when designing the HTS transformer. In the paper we performed study for optimization of winding design to minimize the magnetization loss of HTS winding such as the spaces between pancake windings and operating temperature of HTS wire. The calculation of the AC loss was accomplished by 2-dimensional Finite Element Method.
IEEE Transactions on Appiled Superconductivity 07/2005; · 1.04 Impact Factor
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ABSTRACT: A 1 MVA single phase high temperature superconducting (HTS) transformer was manufactured and tested. The rated voltage of primary and secondary of HTS transformer are 22.9 kV and 6.6 kV respectively. BSCCO-2223 HTS tape was used for HTS windings of 1 MVA HTS transformer. In order to reduce AC loss generated in the HTS winding, the concentrically arranged winding was adopted to 1 MVA HTS transformer. Single HTS tape for primary windings and 4 parallel HTS tapes for secondary windings were used considering the each rated current of the HTS transformer. A core of HTS transformer was fabricated as a shell type core made of laminated silicon steel plate. And a GFRP cryostat with a room temperature bore was also manufactured. The characteristic tests such as no load test, short circuit test and several insulation tests were performed at 65 K using sub-cooled liquid nitrogen. Through these test results, the validity of design of HTS transformer was ascertained.
IEEE Transactions on Appiled Superconductivity 07/2005; · 1.04 Impact Factor
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ABSTRACT: In this paper, 16 HTS pancake coil modules made with 32 double pancake coils were designed, analyzed, built, assembled, and tested to show feasibility of small sized HTS SMES (μ-SMES). Rated current is 200 A and operating temperature is 20 ∼ 30 K. Evolution strategy was used for coil optimization and FEM was used for magnetic field calculation. After building the modular toroid coils, a vacuum chamber was built to contain the coil. Three GM cryocoolers were used to reach the operating temperature. Bridge type converter was used to supply the current to the SMES coil modules. Operation showed a close agreement with the calculated result.
IEEE Transactions on Appiled Superconductivity 07/2005; · 1.04 Impact Factor
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ABSTRACT: AC loss is one of the most important parameters in high-temperature superconducting (HTS) ac devices. Among the HTS ac power devices, the transformer is the essential part in the electrical power system. But unfortunately, the transformer is the worst device concerning ac loss because of very large magnetization loss due to high magnetic field applied to the HTS wire. We calculated the magnetization losses in HTS pancake windings for transformer according to the operating temperature. Two kinds of arrangements of HTS pancake windings were adopted for calculation of ac loss of shell-type transformer, and the analysis results were presented and discussed.
IEEE Transactions on Magnetics 06/2005; · 1.36 Impact Factor
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ABSTRACT: The trapped field variation of a high temperature superconducting (HTS) bulk before and after a crack happens, which was impossible to simulate using 2D analysis method, was calculated in this paper. 3D finite element method (FEM) and iteration method were used to find screening current distribution inside an HTS bulk. In 3D analysis of an HTS bulk with a crack, calculated current distribution inside an HTS bulk should obey the equation of current continuity. For this purpose, ∇φ variable was set to satisfy the equation of current continuity, which was impossible to be considered directly by the FEM governing equation using critical state model. Also, boundary condition at the surface of an HTS bulk was applied to consider the equation of current continuity. Simulation results were compared with experimental ones to verify the validity of the suggested simulation method.
IEEE Transactions on Appiled Superconductivity 07/2004; · 1.04 Impact Factor
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Woo-Seok Kim,
Jin-ho Han,
Sung-Hoon Kim,
Wong-Gee Min,
T. Chang,
Kyeong-Dal Choi,
Hyeong-Gil Joo,
Gye-Won Hong, Song-Yop Hahn,
Jung-Ho Park,
Hee-Suck Song
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ABSTRACT: A 1 MVA single phase high temperature superconducting (HTS) transformer was fabricated and a part of experimental test for characteristics of the transformer was performed. The rated voltages of primary and secondary of the HTS transformer are 22.9 kV and 6.6 kV respectively. BSCCO-2223 wire was used for HTS windings whose shapes are double pancake arranged reciprocally. Single HTS wire for primary windings and 4 HTS wires for secondary windings were used considering the rated current of the transformer. Four HTS wires in secondary windings were transposed at the connection between double pancakes 3 times. The electrical insulation and transport current test were performed at 77 K using liquid nitrogen. The rest of the test for the characteristics of the transformer is in progress.
IEEE Transactions on Appiled Superconductivity 07/2004; · 1.04 Impact Factor
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ABSTRACT: This paper deals with a method for obtaining the transient internal voltage distribution of a transformer. It is essential to consider the frequency-dependent effects of internal capacitance, inductance, and resistance in order to analyze the transient characteristics of a transformer. Frequency-dependent inductance and resistance are obtained from an analytical method and the values match well with the experimental ones. The numerical results of internal transient voltage of a transformer show good agreement with the experimental results from the literature.
IEEE Transactions on Magnetics 04/2004; · 1.36 Impact Factor
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ABSTRACT: To improve computational accuracy and efficiency, the flux-corrected transport scheme on an unstructured grid is proposed as a method of local field approximation plasma display panel (PDP) modeling. The discharge of a PDP macrocell is simulated and the results are presented. After the discussion about the waveform of current and striation phenomena, it is shown that the accuracy of the proposed method is superior to that of a conventional method.
IEEE Transactions on Magnetics 08/2003; · 1.36 Impact Factor
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ABSTRACT: It is common practice to wind coils in pancake shape for conventional high voltage transformers because of electrical insulation problems. In HTS superconducting transformers, the perpendicular component of magnetic flux density (B<sub>r</sub>) applied to HTS tapes of pancake windings becomes larger than that of solenoid winding, thereby decreasing the critical current in the HTS tapes. This paper introduces several methods to reduce B<sub>r</sub> applied to the HTS tapes in the transformer with double pancake windings by changing winding arrangements and the relative permeability of flux diverters. We have conducted a winding design for a single-phase 1 MVA 22.9 kV/6.6 kV HTS transformer. The magnetic field in the spaces occupied by the windings and its vicinity was numerically simulated. We observed a change of B<sub>r</sub> due to various gap arrangements of high voltage and low voltage windings and various reciprocal arrangements. We also observed a change of B<sub>r</sub> on the HTS tapes due to variation of relative permeability of flux diverters placed between the high voltage winding and the low voltage winding.
IEEE Transactions on Appiled Superconductivity 07/2003; · 1.04 Impact Factor
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ABSTRACT: A 1 MVA transformer using BSCCO-2223 high T<sub>c</sub> superconducting (HTS) tapes was designed. The rated voltages of each sides of the transformer for primary and secondary are 22.9 kV and 6.6 kV respectively. Double pancake HTS windings, which have advantages of insulations and distribution of high voltage, were adopted. Four HTS tapes were wound in parallel for the windings of low voltage side. Each winding was composed of several double pancake windings and four parallel conductors of secondary winding were transposed in order to distribute the currents equally in each conductor. The core of the transformer was designed as a shell type core made of laminated silicon steel plate and the core is separated from the windings by a cryostat with a room temperature bore. Configuration of the cryostat made of nonmagnetic and nonconducting material and a liquid nitrogen sub-cooling system were used in order to maintain the coolant's temperature of 65 K.
IEEE Transactions on Appiled Superconductivity 07/2003; · 1.04 Impact Factor
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ABSTRACT: This paper describes an effective method to calculate hysteresis loss of high-temperature superconducting (HTS) bulk material under time varying magnetic field. In the proposed method, the inner product of current and electric field in a HTS bulk is integrated to calculate hysteresis loss. To consider the nonlinear relation between the current and the electric field of HTS bulk material, critical state model and iteration method are adopted. According to the critical state model, if different types of time varying magnetic field are applied, the current distribution in a HTS bulk is affected not by applied field types but by peak-to-peak field values on the assumption of same critical current density regardless of different field types. This is the basic idea to compute hysteresis loss more effectively. This paper shows how to reduce total calculation time using the suggested method. To verify the validity of the suggested method, numerical results are compared with experimentally measured ones.
IEEE Transactions on Appiled Superconductivity 07/2003; · 1.04 Impact Factor
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ABSTRACT: Due to its special structure, the distribution of magnetic fields in a permanent-magnet starter motor with auxiliary poles becomes complex and more affected by the relative position between the stator and rotor than that in an ordinary permanent-magnet starter motor. A two-dimensional finite-element method (FEM), with the effects of relative position and commutation taken into account, is proposed to improve the accuracy of performance analysis. Optimization of the magnetic pole was performed by the proposed FEM. The experimental results showed good agreement with the calculated results, and the cost of the magnetic pole was greatly reduced, while the performances were improved.
IEEE Transactions on Magnetics 06/2003; · 1.36 Impact Factor
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ABSTRACT: The discharge phenomena in corona device was simulated with a
transient approach up to the dynamic steady state. The proposed
transient approach requires neither Kaptsov's assumption nor roughness
factor. As a simple numerical example, the corona discharge between two
concentric cylindrical electrodes was analyzed for two different applied
voltages in the one-dimensional model. The results were presented and
compared with those of the conventional method. To our knowledge, this
is the first work that attempts to simulate the corona discharge up to
the steady state with a complete transient approach
IEEE Transactions on Magnetics 04/2002; · 1.36 Impact Factor
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ABSTRACT: In this paper, optimization of an HTS SMES coil as a part of a 200-kJ HTS SMES system has been realized. A 1+1 evolution strategy with the line element method was used to optimize the shape of the coil. In order to ensure the desired energy storage capacity, final dimensions of the coil were recalculated with the finite element method (FEM).
IEEE Transactions on Appiled Superconductivity 04/2002; · 1.04 Impact Factor
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ABSTRACT: This paper described construction and test results of a 10 kVA HTS transformer. Three phase transformer with double pancake windings were constructed. BSCCO-2223 wire, silicon sheet steel core and FRP cryostats were used in that transformer. After the test of basic properties of the 3 phase HTS transformer using no load test, short circuit test and full load test, continuous operation of 100 hours with pure resistive load has been carried out. Test results proved overload capability and reliability of the HTS transformer.
IEEE Transactions on Appiled Superconductivity 04/2002; · 1.04 Impact Factor
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ABSTRACT: A new flywheel energy storage (FES) system that has a heavy flywheel which rotated in low angular velocity was proposed. In this FES, an induction machine of which the winding connection was controllable was used to eliminate the power converter from the conventional FES system. This reduced the total cost of the FES system, because the price of the electronic power converter is a large part of the total FES system cost. In this paper, the new system configuration was proposed and the operation of the suggested FES system using the induction motor/generator was explained in detail. A new levitation system which consisted of the HTS wire and bulks was proposed. This levitation system was designed to produce a very high levitation force to store the same amount of energy compared to that of the high-speed conventional FES system. At the end of the paper, a conceptual design of a 5 Mj low-speed large-inertia FES system with an induction motor/generator was done.
IEEE Transactions on Appiled Superconductivity 04/2002; · 1.04 Impact Factor
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ABSTRACT: High Tc superconducting (HTS) wires were applied to primary coils of a small size permanent magnet linear synchronous motor. Three-phase racetrack shaped test coils were fabricated and tested. The HTS coils were cooled down to 33 K by using a GM-cryocooler in order to overcome the decrease of the critical current density due to high intensity of magnetic field in the coil. A vacuum chamber and thermal shield for reduction of the radiation and the convection heat penetrations were fabricated. The parameters of the linear motor were calculated by using finite element method, and verified by experiment. It is possible to achieve large thrust force compared with that of a conventional machine because large current can flow in HTS primary coil.
IEEE Transactions on Appiled Superconductivity 04/2002; · 1.04 Impact Factor
