Experimental Results of a 7-T Force-Balanced Helical Coil for Large-Scale SMES

• Published in: IEEE transactions on applied superconductivity Vol. 18; no. 2; pp. 701 - 704
• Main Authors: Nomura, S., Kasuya, K., Tanaka, N., Tsuboi, K., Tsutsui, H., Tsuji-Iio, S., Shimada, R.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01-06-2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Coiling; Coils (windings); Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electromagnetic forces; Electromagnets; Energy accumulation; Exact sciences and technology; Excitation; helical coil; Large-scale systems; Liquid helium; Niobium base alloys; Niobium compounds; quench properties; Reinforcing materials; Samarium; SMES; Solenoids; Strands; Superconducting coils; Superconducting magnetic energy storage; Superconductivity; Titanium compounds; Toroidal magnetic fields; Various equipment and components; Wounds; Thermal stress; Cooling by liquid; Electric stress; Electromagnetic forces; Critical field; Learning; Inductance; Critical current; helical coil; Strand; quench properties; Superconducting magnet energy storage; Magnetic energy; Machine windings; Negative bias temperature instability; Electromagnetic force; Toroidal field; Experimental study; Superconducting coils; SMES; Solenoid; Stainless steel; Coil spring; Large scale; Reliability; Energy storage
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2008.920552

A superconducting force-balanced coil (FBC), which is geometrically one tenth the size of a 100 MJ class SMES coil, has been developed. The FBC is a helically wound hybrid coil of toroidal field coils and a solenoid. This coil configuration can minimize the required mass of the structure for induced electromagnetic forces. The model FBC with an outer diameter of 0.53 m will have 270 kJ magnetic energy at the critical magnetic field of 7.1 T using NbTi strands. The critical coil current and self inductance are 552 A and 1.8 H, respectively. The diameter of the NbTi strand is 1.17 mm. The hand-made winding of the model FBC was carried out without reinforcing materials such as stainless steel wires. The first experiment was conducted with liquid helium cooling. The quench properties of the model FBC were mainly investigated. The first quench current is 293 A, which is 53% of the critical coil current. Training phenomena were observed in the model FBC without any sudden decreases in the quench current. After 33 successive excitations the quench current improved to 419 A, and it was successfully excited up to 5.4 T without reinforcing materials for the NbTi strand. This fact demonstrates a primary capability of the FBC as a SMES coil.