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The application of superconductivity technology to electric power apparatus is very important from the viewpoint of energy saving. Especially, the superconducting generators using superconductors as the field windings have many merits compared with conventional generators. Super‐GM has been researching and developing 70‐MW‐class model machines since FY 1988 for a scheduled period of eight years, aiming at a 200‐MW‐class superconducting generator. This paper describes the basic specifications and designs of 70‐MW‐class superconducting generators by Super‐GM and also describes the propriety of these basic specifications and designs.

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The development of large-current-capacity AC superconducting cables is an important step in the realization of AC superconducting power apparatuses. We have developed and tested a kA-class AC superconducting cable, bundled and twisted with 343 (7 x 7 x 7) strands. The measured AC quench current is much smaller than the sum of the critical current of each strand. We are strand are given as follows, using two parallel straight conductor inductance equations: _,lab dqj$7 theoretically and experimentally investigating the causes of this current degradation. There are several possible 4 3 ky k d 2causes of the degradation, such as temperature rise due to AC losses and mechanical vibration, nonuniform current distribution among strands due to inductance imbalance and magnetic instability ([I]). Of these causes, we focus our research effort on the nonuniform current distribution among the strands and measure the current distribution current distributions are compared with theoretical ones, and the component of AC quench current degradation is discussed. Fig.1 The cable cross section and the number of each strand (1) ( 2 ) among strands of a cable. In this paper, the measured 21 3 L = 21(iOg ---) x + L, M = 21(iOg --1) x 1 0 -~ + M,,,, a 4 21 d