Heecheol Park

De-Lamination Characteristics of Coated Conductor for Conduction Cooled HTS Coil

According to the continuous development of coated conductors and compact cryocoolers, research and development efforts for High Temperature Superconducting (HTS) magnets are increasing using conduction cooling method. To increase the cooling efficiency and thermal stability of the HTS magnet, the coated conductor is wound by wet-winding or epoxy impregnating in vacuum after dry-winding. Due to the large Lorentz force and thermal contraction, stress analysis of the composite material, which is composed of HTS conductor, insulation layer and epoxy layer, is necessary to assure the mechanical stability of the HTS magnets. Mechanical strength for a/b axis, which is parallel to the conductor surface, is usually strong enough to endure the large tensile stress due to the tough substrate material. However, c-axis strength, which is perpendicular to the conductor surface, is not strong enough to ensure the large Lorentz force. The de-lamination of the multi-layered HTS tape in a coil structure can occur and the results were previously reported. Therefore, the test data for allowable c-axis strength is necessary to design the mechanical stability of the HTS coil. This paper describes the experimental results for the c-axis tensile strength of various coated conductors. The results show the wide divergence of the c-axis tension force from 18 MPa to 53 MPa. Through the FEM analysis for multi-layered structure of the HTS tape, concept design for HTS tape of enhanced c-axis strength is suggested.

Delamination Characteristics of Single Layer and Stacked HTS Coated Conductor for Conduction Cooling Application

For the conduction cooling of HTS magnets using coated conductor, the coils are either wet-wound or vacuum impregnated by cryogenic epoxy after dry winding. It is known that the magnet can be degraded after cool down due to delamination of the conductor. There have been several experimental investigations on the weak c-axis strength of the coated conductor. The structural delamination characteristics of the stacked conductor are also important for the design of mechanically stable conductively cooled HTS coil such as HTS generators, HTS motors, and SMES. C-axis tension experiments were performed with narrow soldering anvils to investigate the different delamination strengths at the edge and center of the conductor. FEM analysis was carried out to investigate the thermal stress caused by the different thermal expansion coefficients of several components of HTS coil for conduction cooling. The results of our analysis suggest possible coil configuration changes to avoid excess tensile stress at the edge of the conductor.

Performance Analysis of a 10-kW Superconducting Synchronous Generator

POSCO and the Research Institute of Industrial Science and Technology developed a 10-kW superconducting synchronous generator using high-temperature superconducting wire. The generator consists of four-pole racetrack-type superconducting coils using GdBCO wire for rotor and 24 slots copper windings for stator. The rated power of the generator was 10 kW at 600 r/min, and the operating temperature was 30 K by thermosyphon cooling method using liquid neon. The output power was measured when the generator was connected to a vector motor, and the detailed results were discussed in this paper.

Development of CICC for KSTAR TF coil system

The KSTAR (Korea Superconducting Tokamak Advanced Research) superconducting magnet system consists of 16 TFs (Toroidal Field) and 14 PFs (Poloidal Field) coils. Internally-cooled cabled superconductors will be used for the magnet system. The magnet systems adopt a superconducting CICC (Cable-In-Conduit Conductor) type conductor. The KSTAR TF CICC uses Nb/sub 3/Sn superconducting cable with Incoloy 908 conduit. For the fabrication of TF 1/spl sim/3 CICC, cables have been fabricated and the cable has a length of 640 m and a diameter of 22.3 mm. A continuous CICC jacketing system is developed for the CICC jacketing and the jacketing system uses the tube-mill process, which consists of forming, welding, sizing and squaring procedures. The cabling and the jacketing process is described. The welding condition of the Incoloy 908 and design specification of CICCs are also discussed. The fabrication results including the geometrical specification and the void fraction will be discussed.

Development of CICC for KSTAR Superconducting Magnet System

The KSTAR (Korea Superconducting Tokamak Advanced Research) superconducting magnet system adopts a superconducting CICC(Cable-In-Conduit Conductor) type conductor. It consists of 16 TF (Toroidal Field) coils and 14 PF (Poroidal Field) coils and it also uses two different types of CICCs-Nb3Sn cable with Incoloy 908 conduit and NbTi cable with 316LN stainless-steel conduit. A special CICC jacketing system is developed for the KSTAR CICC fabrication: the tube-mill process, which consists of forming, welding, sizing and squaring procedure. The cabling process for TF and PF superconducting cable and the fabrication process of each CICCs (TF CICC and PF CICC) is described. The welding of conduit materials are also discussed. The fabrication results such as the geometrical specification, micro structure and the void fraction will be discussed

Design and Characteristic Analysis of a 10 kW Superconducting Synchronous Generator for Wind Turbines

A superconducting synchronous generator (SCSG) is suitable for designing a large-scale wind power generation system, because of its lighter weight and higher torque as compared to conventional generators. This paper analyzes a 10-kW SCSG designed by the finite element method. The finite element method tool is used to evaluate the designed 10-kW SCSG, which has 16 double pancake coils of race-track type with coated conductor tape according to the component certification (IEC 60034) for a wind power generator. The results show several specific characteristics of the designed SCSG. The results can also effectively evaluate the SCSG for a wind turbine, before the scale-up design and fabrication of the generator.

Thermohydraulic simulation on CIC conductor with adaptive mesh finite volume method for KSTAR tokamak superconducting magnet

To study the quench in the CICC, the numerical analysis code was developed. The fully implicit time integration of upwind scheme for finite volume method is utilized to discretize the equations on the staggered mesh. The scheme of adaptive mesh is proposed for the moving boundary problem and the time term is discretized by the /spl theta/-implicit scheme. The discretized equations are solved by the IMSL. The error analysis of this method is performed by various step-sizes of time and space. The thermal hydraulic behavior of the CICC used in KSTAR is studied.

Induced voltage and alternating current loss in superconducting magnet system for SSTF

The induced voltage in the Samsung Superconducting Test Facility (SSTF) is analyzed according to the calculation of self-inductance and mutual inductance. The voltage induced by blip and compensating coils in the main coils is about 6.4 V. In order to charge the main coils, the power supply must provide the minimum voltage of 1.1 kV. The compensating coils have an influence on the field distribution. The compensating coils result in the decreasing center field about 2.67%. AC losses that include the coupling, hysteresis and eddy losses are calculated in the main, blip and compensating coils. It leads to the temperature rise of about 8 K in main coils.

Thermal and Mechanical Design of a HTS Quadrupole Magnet of In-Flight Fragment Separator for Rare Isotope Science Project (RISP)

An in-flight fragment (IF) system is used to produce and investigate an isotope beam of interest from heavy-ion accelerators, and it is composed of prestages and main stages. A quadrupole magnet of an IF preseparator is located in a high-radiation region, and the neutron radiation heat load is much larger than that of common superconducting magnets. Considering the efficiency of a cooling system, high-temperature superconducting (HTS) magnets are preferred to low-temperature superconducting magnets. To remove the large radiation heat load, the circulation of cold helium gas is used instead of conduction cooling. Pressurized helium gas circulates in cooling channels, and the optimized design of a cooling structure is required. Moreover, large Lorentz force is generated in the coil, and an appropriate supporting structure should be designed within the allowable conduction heat loss through the supporting structure. This paper describes the thermal and mechanical design of the REBCO HTS quadrupole magnet. Structural design is carried out considering the Lorentz force of the HTS magnet. Thermal analysis is also performed to estimate the heat loss using the designed structure. Finally, the design of a cooling system is carried out to keep the magnet temperature under 40 K against the estimated heat loss.

Jacketing and repair of the KSTAR CICC

The KSTAR (Korea Superconducting Tokamak Advanced Research) superconducting magnet system which consists of 16 TF coils and 14 PF coils adopts a superconducting CICC (Cable-In-Conduit Conductor) type conductor. The KSTAR magnet system uses two different types of CICCs-Nb/sub 3/Sn cable with Incoloy 908 conduit and NbTi cable with 316LN stainless-steel conduit. A continuous CICC jacketing system is developed for the KSTAR CICC fabrication and the jacketing system uses the tube-mill process. It consists of forming, welding, sizing and squaring procedures. The welding condition of CICCs and the fabrication process is described. The repair of the CICC is also discussed.