A HTS induction motor, with a HTS squirrel-cage rotor, is analysed using an electrical equivalent circuit. The squirrel-cage winding in the rotor consists of rotor bars and end rings, and both are considered to be made of YBCO film conductors. A wide range of electric field versus current density in YBCO film is formulated based on the Weibull function, and analysed as a non-linear resistance in the equivalent circuit. It is shown that starting and accelerating torques of the HTS induction motor are improved drastically compared to those of a conventional induction motor. Furthermore, large synchronous torque can also be realized by trapping the magnetic flux in the rotor circuit because of the persistent current mode.

HTS squirrel-cage induction motor was fabricated and tested in this study. Both of rotor bars and end rings were made of Bi-2223/Ag multifilamentary tapes in order to realize superconducting current loops, and the conventional (normal conducting) stator, 3-phase and 4-pole, was utilized. Rotating characteristics of the fabricated motor were tested for different input voltages at 60 Hz. The performances were also analyzed by means of the theoretical method based on the electrical equivalent circuit. It was shown that the minimum starting voltage was experimentally confirmed and agreed semi-quantitatively with the analysis result. The rotation at synchronous speed was realized by applying the load, at least, 1.5 Nm.

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