Development of 50-kW-Class High-Temperature Superconducting Induction/Synchronous Motor With Continuous Drive Characteristics from Room Temperature

We investigate the rotational characteristics of a 50-kW-class high-temperature superconducting induction/synchro- nous motor in superconducting and non-superconducting states. The prototype motor was first placed in liquid nitrogen, and the efficiency contour was obtained. The liquid nitrogen was then gradually removed from the motor under the partial load (10 kW) condition. This showed that continuous operation is possible even at temperatures exceeding 130 K. Furthermore, we succeeded in driving at 11% of the rated output, even at room temperature. As a result, a practical high-temperature superconducting motor that can continue to operate with reduced output even when the cooling system fails could be realized

Influence of Gas Flow and Improvement of Homogeneity on the Distribution of Critical Current Density in YBCO Coated Conductor Processed by TFA-MOD Method

AbstractUsing a scanning Hall-probe microscopy, we have investigated in-plane distribution of critical current density in TFA-MOD processed YBCO coated conductors. We compared the distributions of critical current density for two kinds of coated conductors processed with different directions of gas flow at the calcinations. As a result, it was found that the direction of the gas flow largely influenced the distribution of critical current density. For example, the maximum value of critical current density was 1.5 times higher than the average for a sample processed with a gas flow in width direction. On the other hand, the distribution of critical current density was relatively uniform for the one with a gas flow in axial direction perpendicular to the surface of the conductor. These findings will be very important information for the optimization of the manufacturer processes for the conductors. Actually, a very uniform distribution of critical current density has been observed for a coated conductor produced by an optimized process. This demonstrates a high potential of TFA-MOD processed YBCO coated conductors for practical applications

Transport properties of multifilamentary Ag-sheated Bi-2223 tapes under the influence of strain

Current-voltage (I-V) characteristics in multifilamentary Ag/Bi2223 tapes are investigated as a function of mechanical strain. As is well known, the critical current, Ic, in axially elongated tape remains almost constant up to a strain around 0.5%, then is followed by a sharp reduction. However, for larger elongations, a long tail in the Ic-strain curve is observed, i.e., around 20% of the initial Ic still remains even at 0.8% strain. The irreversible Ic reduction indicates that the degradation comes from the breakdown of superconducting filaments. However, it is observed that the rupture risk probability reduces as the strain is increased in the long tail. This anomaly suggests that the measured strain of the whole tape is not identical to that of the HTS filaments inside the tape. We propose a model to describe the mechanical properties of the tape. It is shown that (1) the breakdown probability of the filaments is well described by the Weibull function if we calculate the influence of shearing between the superconducting filaments and the surrounding Ag sheath, (2) the Ic-strain properties can be described accurately by the model, (3) transport I-V characteristics can also be described simultaneously as a function of strai