AC loss performance of the 100 kWh SMES model coil

AC loss tests of the SMES model coil for 100kWh SMES pilot plant were carri ed out at Lawrence Livermore National Laboratory (LLNL) in 1998, in collabo ration between Japan and the USA. The AC loss results at LLNL were in good agreement with those obtained at the Japan Atomic Energy Research Institute (JAERI) in 1996. The coupling loss in the coil could be described by two c omponents with a short time constant (0.22s) and a long time constant (30s) . The short time constant was in good agreement with that measured in a sho rt sample. The signals of Hall probes, mounted on the surface of the coil, revealed that the induced loop currents in the conductor decayed with long time constants. At least two long time constants were observed: about 4s an d 100s. The long time constant was also identified by the observation of vo ltage decay after the coil discharge. These loops result in the additional AC loss in the coil. Effect of lateral force in the cable on losses was stu died as well. An improved conductor aiming to reduce the AC loss was-design ed, fabricated and wound in a small coil. The measured AC loss in the small coil made of the improved conductor was about 1/6 of the SMES model coil p er strand volume.