Thursday, 1A-08, 5:35-5:50

Development of REBCO Superconducting Transformers and Motors in Japan

M. Iwakuma

H. Hayashi², H. Okamoto², Y. Hase³, T. Satou³, A. Tomioka⁴, M. Konno⁵, Y. Iijima⁶, T. Saitoh⁶, Y. Yamada⁷, T. Izumi⁷ and Y. Shiohara⁷

¹Kyushu University, Fukuoka 819-0395, Japan; ²Kyushu Electric Power Co. Inc., Fukuoka 815-8520, Japan; ³Japan Motor & Generator Co. Ltd., Tokyo 101-0054, Japan; ⁴Fuji Electric Advanced Technology Co. Ltd.. Hino 191-8502, Japan; ⁵Fuji Electric Systems Co. Ltd., Tokyo 141-0032, Japan; ⁶Fujikura Ltd., Tokyo 135-8512, Japan; ⁷Superconductivity Research Laboratory, Tokyo 135-0062, Japan

In Japan we started a national project to develop superconducting power machines and devices with REBCO superconducting tapes two years ago. In this workshop I will report the progress of the development of transformers and motors.

The target transformer is a 66/6.9kV-20MVA one for a substation in a power grid. Superconducting transformers are expected to give us the merits of compactness, lightweight and high efficiency. To produce such merits, it is necessary to reduce a 1-turn voltage, which is the important parameter for the design of a transformer, in comparison to conventional transformers. It corresponds to increasing the turn number of windings and reducing the cross-sectional area of an iron core. By making the most use of low loss and high Jc properties of superconducting tapes, the superconducting windings will be compact even if the turn number increases. We proposed a new idea to reduce the ac loss in REBCO superconducting thin tapes and verified it even in coil configuration. In addition, in order to satisfy the dielectric strength regulated in Japanese standards on transformers, we got the data on the basically required insulation distance in the peculiar system which are mainly composed of REBCO thin tapes and subcooled liquid nitrogen. Further we verified the applicability of the method of enhancing the current capacity by forming transposed parallel conductors with REBCO thin tapes though the tapes are bent edgewise at transposition points.

As for motors, we successfully fabricated a 7.5kW@360rpm motor with a superconducting rotor with REBCO tapes. The rotor was cooled down to 40K by forced-flowed helium gas. 6-pices of field coils were racetrack-shaped 19-layer solenoidal ones. The armature winding was wound with copper wires. We carried out the factory test in the same way as conventional motors. We confirmed 11kW power output applying the field current up to 70A beyond the design one of 60A.

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