S. Yamada

T. Mito

National Institute for Fusion Science (NIFS-Repository)

§ 10. Development of Superconducting Bus Line Mito, T., Yamada, S. A flexible superconducting bus-line is proposed as an electrical feeder between the superconducting coils of the Large Helical Device (LHD) and the device's power supplies. The bus-line consists of superconducting cables and a cryogenic flexible transfer-line. A specially developed aluminum sta-bilized NbTi/Cu compacted strand cable satisfies requirements for large current capacity, high stability, high reliability and flexibility. A full-scale model with a length of 20 m was designed and con-structed to investigate the feasibility and perfor-mance of the superconducting bus-line. Its fabrication, transportation, installation, cooling and excitation tests were successfully carried out. Fabrication and installation of the full-scale model of the flexible superconducting bus-line were successfully carried out. Most parts of the superconducting bus-line were assembled in the factory. The assembled bus-line was then transported and installed at the experimental site. The full-scale model was cooled down and excited successfully up to 40 kA without a quench. The measured minimum propagation current was larger than 32.5 kA. Thus, the bus line was fully stabilized at the rated current of 30 kA. A specially developed aluminum stabilized NbTi/Cu compacted strand cable was demonstrated to be sufficiently stable for the bus line. The measured current distribution of the nine-stand cable was quite uniform. The success of the full-scale model shows the feasibility and usefulness of flexible superconducting bus-lines for LHD and in other applications, too. Flow Channels CD Liquid Helium CZ@Vacuum @ Helium Gas Stainless Steel Corrugated Tube ~ 130mm /~ 143mm I \ Stainless Steel Corrugated Tube f 198mm If 220mm Fig. 1. Configuration of a flexible superconducting bus-line. 16 TABLE I Specifications of Bus-Lines for LHD and Full Scale Model l. Rated current 2. Breakdown voltage (in helium gas at l atm, 77K) 3. Length 4. Conductor 5. Minimum bending radius 6. Transfer-line 7. Outer diameter 8. Cooling method 9. Heatload Liquid helium channel Returning gas channel 80 K shield gas channel For LHD Full scale (updated design) model 13kA-3lkA 30kA for Poloidal coil DC2kV DC5kV (design) for Helical coil >DC 5 kV DC2kV (measured) 45 m- 65 m 20m Aluminum stabilized NbTi/Cu compacted strand cable 1.5m 1.5m Coaxial five-channel with 80K shield <0.25 m Four-channel 0.22m Forced-flow of two-phase helium < 0.2 W/m <0.2 W/m <3 W/m < 0.3W/m < 3.5 W/m TABLE 2 Parameters of Superconducting Cable for Bus-Line Aluminum Stabilized, Compacted Strand Cable 1. Rated current 30 kA at 1 T, 4.2 K 2 . Critical current 180 kA at 1T, 4.2 K 3. Size 17.2 mm x 35.4 mm 4. Number of strands 9 5. Twist pitch of strands 374 mm 6. Electrical Insulation Polyamide paper (nomex) 7. AI sectional area 500 mm2 8. Cooling ratio 13 % of the cable surface 9. Minimum propagation 40 kA current Superconducting Strand 1 . Outer diameter 8.95 mm 2 . NbTi/Cu insert diameter 3. AI:Cu:NbTi ratio 4. Twist pitch of filaments 5 . Filament diameter 6. NbTi/Cu critical current density 7. AI resistivity References 2.91 mm 8.4:0.5:0.5 60mm 30 J..Lm 6000 A/mm2 at 1 T, 4.2 K 3 X w-11 Qm at 1 T, 4.2 K 1) Mito, T. et al. "Conceptual design and development of a superconducting bus-line for the Large Helical Device." Fusion Engineering and Design, Vol. 20, 1993, pp.113-120. 2) Mito, T. et al. "Development and tests of a flexible superconducting bus-line for the Large Helical Device." Proceedings of MT -13 to be published. 

Development of Superconducting Bus Line

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