Young-Kil Kwon

High temperature superconducting synchronous motor

This paper deals with high temperature superconducting (HTS) synchronous motor, which has two characteristics: the HTS magnet with iron plates as field coil, and the solid nitrogen (SN/sub 2/) as a cryogen. The HTS magnet has iron plates to achieve the maximum current-carrying capacity and the simple shape that can easily be wound and jointed. The HTS magnet with iron plates, magnet optimized current distribution, and initial magnet are presented through FEA (finite element analysis), manufacturing and testing these magnets. SN/sub 2/ is employed for keeping the operating temperature of HTS synchronous motor. To make the SN/sub 2/ of liquid nitrogen (LN/sub 2/), liquid helium (LHe) passes into the heat exchanger and cools its own temperature. Two types of heat exchangers are designed and manufactured to make the SN/sub 2/, and each of the temperature characteristics is compared.

Study on Homopolar Superconductivity Synchronous Motors for Ship Propulsion Applications

Superconductivity synchronous motors compared with conventional motors can reduce the motor size and enhance the motor efficiency for low-speed and high torque applications under the space constraints for propulsion system. Especially, homopolar superconductivity synchronous motors (HSSMs) need less superconductor and lower magnetic flux density in superconductor field coil than air-cored superconductivity synchronous motors (ASSMs). In addition, mechanical structure is more simplified and stability is increased because the superconductor field coil of HSSMs is not rotated in operation. In this paper, we present the outline of HSSMs including structure, characteristics and operational principles with the conceptual design of HSSM.

Parametric Design for Superconducting Synchronous Motor With 3D Equivalent Magnetic Circuit Network Model

This paper proposes an effective parametric design for high temperature superconducting (HTS) synchronous motors with 3D equivalent magnetic circuit network (EMCN) method. Proposed design process consists of 5 steps which are electric design, mechanical design, characteristic analysis for field and armature, and motor characteristic analysis. Especially, in order to predict the performance of HTS synchronous motors, the variation of output power characteristics according to the variation of back electromotive force (BEMF) and inductance is analysed in electric design. Reliability of proposed design process and developed program is verified through the comparison of the results of commercial program using 3D finite element analysis (FEA) method.

Optimal Design of Superconducting Motor to Improve Power Density Using 3D EMCN and Response Surface Methodology

This paper proposes an effective design process for 1 MW HTS superconducting motor by using 3-dimensional equivalent magnetic circuit network method (3D EMCN) and response surface methodology (RSM). During the process, 3D EMCN is used with a simplified 3D analysis model to get electric parameters in short time. RSM is used for the motor optimal design to improve power density. The usefulness of this method is verified through the comparison of the performances of the optimal geometry and those of the initial geometry

Design and electrical characteristics analysis of 100 HP HTS synchronous motor in 21st Century Frontier Project, Korea

A 100 hp class superconducting motor in the 21st Century Frontier R&D Program of Korea has been designed. A theoretical model of high temperature superconducting (HTS) motor was presented by two-dimensional electromagnetic field analysis. The motor is composed of HTS field winding, cold damper shield, air-gap armature winding and laminated machine shield. The HTS field winding consists of racetrack type double pancake coils wound with Bi-2223 HTS tapes operated at about 30 K. The operating current of the HTS tape conductor could be determined by the magnetic field distribution calculated in the HTS field winding and the I/sub c/ - B characteristics of a practical HTS conductor, taking account of its anisotropy.

Load line analysis of Bi-2223 tape-stacked-cable for self field effects

In general, the critical current of a Bi-2223 tape-stacked-cable is much less than the total summation of critical currents of each tape, which is mainly due to the self magnetic fields of the cable itself. Therefore, to predict the critical current of a Bi-2223 tape-stacked-cable, we need to analyze the self field effects of the stacked cable as well as the critical current density data (J/sub c/) of one tape. To make it more complex, the critical current degradation of a Bi-2223 tape is anisotropic; the critical current is lower in the normal magnetic field (to the tape surface) than in the parallel field. In this paper, a novel approach to predict the critical current of a Bi-2223 tape-stacked-cable from a J/sub c/-B curve of one tape is presented. The approach basically includes the load line analysis of the stacked tapes, and its usefulness is confirmed by the experimental data.

Thermal Quench in HTS Double Pancake Race Track Coil

In large scale applications, such as SMES, motors and generators, High Temperature Superconducting (HTS) magnets are constructed with many stacks of the double-pancake coils connected in series. In spite of its higher thermal stability, HTS magnet can experience a severe quench, which can resulted from a very small portion. From HTS magnet design point of view, it is very important to predict the possibility of occurrence quench in the designed magnet to provide a suitable quench protection device. In this paper a highly instrumented HTS race track double-pancake coil was prepared to examine the quench development characteristics. It is wound using the Bi-2223 tape. Many voltage taps, cryogenic thermocouples and heater were installed in the winding. Conduction cooling method is adapted for the convenience of temperature. Quench development in the coil was measured under different operating current. The experimental details and results are presented in this paper.

Influence of Non-Uniform Current Distribution on AC Transport Current Loss in Bi-2223/Ag Tapes

This paper presents the influence of current distribution on AC transport current loss in multi-strand high-temperature superconductor (HTS) tapes. The current-distribution-dependent-AC loss is analyzed by introducing a current distribution parameter. We calculated AC loss of multi-strand HTS tapes numerically and performed AC loss measurements as well. Though the effect of current distribution on AC transport current loss is relatively insignificant for a low applied transport current, the effect of nonuniform current distribution seriously increases AC loss for a high applied transport current. The AC loss measurement method used in this paper is also confirmed by comparison with numerical results: the experimental and computational results showed good agreement for various current distribution parameters

Performance evaluation of HTS synchronous motor using finite element method

A 100 HP rated synchronous motor with superconducting rotating field winding has been designed based on the formulated equations established from 2 dimensional magnetic field distributions in a cylindrical coordinate. The cross-section was drawn based on calculated design results via Fortran program and then modeled with FEM (finite element method) to investigate the machine performances. First of all, the magnetic field distributions are analyzed in many ways according to the field directions and the armature currents. Especially after the rotating field winding is arranged with BSCCO-2223 high-temperature superconducting (HTS) pancake coils, the exerted magnetic field normally on the HTS tape is calculated through FEM. And the machine output power is calculated according to the torque angles that lie between the field and the armature main flux lines. Moreover, this paper includes the eddy-current loss variations of a copper damper located between the field and the armature coils. Finally, 3 dimensional magnetic field distribution is also calculated via FEM. The radial components of magnetic field are compared along the center line of an armature conductor section between 2 dimensional and 3 dimensional results. By the comparison we make sure that about 30% of machine output is added from the end effect of HTS field coil and more accurate design approach is possible.

Design of high temperature superconducting magnet

It is well known that I/sub c/ (critical current) in high temperature superconducting (HTS) materials is more sensitive to magnetic fields perpendicular to the wide face of the HTS tape (B/spl perp/) than to fields parallel to that (B//). Thus, in shape design of the HTS magnet, a method to reduce the value of B/spl perp/ should be considered. This work presents a racetrack HTS magnet with iron plates to achieve the maximum current-carrying capacity and the simple shape that can easily be wound and jointed. The shape, position, and kinds of iron plates are chosen by way of 3 Dimensional Finite Element Analysis (3-D FEA) considering magnetic saturation of iron plates. The racetrack HTS magnet with iron plates, a magnet having optimized current distribution and an initial magnet are compared with each other through 3-D FEA, manufacturing and testing of these magnets. The current capabilities of HTS magnet with iron plates improved by 50% on the basis of the initial magnet.