Our research group have proposed the introduction of transposed parallel conductors which are generally used in conventional electric power machines and devices in order to realize a large current capacity, uniform current sharing and low AC loss. In previous studies, the additional AC loss due to the formation of the parallel conductors composed of two REBa2Cu3Oy (REBCO) superconducting tapes was investigated by pickup-coil method. In this study, three-strand parallel conductors were measured and compared with theoretical predictions. The objective of this study is to clarify the additional AC loss properties of three-strand parallel conductors composed of REBCO tapes and to prove the validity of the theoretical expressions via experiment.
The theoretical expressions of the AC loss assumed that the voltage-current characteristics are expressed by the n-value model. The samples of REBCO superconducting tapes were provided by Sumitomo Electric Industries, Ltd. The total thickness, width, critical current and n-value are 178 μm, 2.1 mm, 100 A and 25-30 at 77.3 K, respectively. The three insulated REBCO strands were co-wound into one-layer solenoidal coil. They were soldered at both ends. Three kinds of sample coils were prepared: non-transposed sample, once transposed sample and twice transposed sample.
The non-transposed sample was already measured and compared with the theoretical predictions. The observed AC loss roughly corresponded with the theoretical predictions. Furthermore, the current distribution of three-strand will be investigated using Rogowski coils.
This research was partially supported by the Japan Science and Technology: Advanced Low Carbon Technology Research and Development Program and the Japan Society for the Promotion of Scienve: Grant-in-Aid-for Scientific Research (JP18H03783 and JP17H06931).