David Thomas Ryan

AC losses in a high temperature superconducting generator

As part of the DOE-SPI funded project a commercial HTS utility-size generator is being developed based on GEs iron core superconducting generator technology. The iron core concept has significant advantages over air core designs. The rotor consists of a cold superconducting field coil and coil supports and a warm iron core, which takes the torque and transmits to the shafts. Heat load due to AC losses in the cold mass of the rotor are a key design constraint. Analyses have been performed both at the component and system levels. AC loss tests have been conducted on an HTS generator. This paper presents and discusses the analytical and test results.

Critical current degradation in HTS wires due to cyclic mechanical strain

HTS wires, which may be used in many devices such as magnets and rotating machines, may be subjected to mechanical strains from electromagnetic, thermal and centripetal forces. In some applications these strains will be repeated several thousand times during the lifetime of the device. We have measured critical current degradation due to repeated strain cycles for both compressive and tensile strains. Results for BSCCO-2223 HTS conductor samples are presented for strain values up to 0.5% and cycle numbers up to and beyond 10/sup 4/.

Suitability of MgB/sub 2/ tapes with iron sheaths for multiturn superconducting coils

This paper investigates the suitability of MgB/sub 2/ tapes clad in a high magnetic permeability iron sheath for use in practical multi-turn superconducting coils. The flux-density in the MgB/sub 2/ portion of a single filamentary tape under various configurations is analyzed and its effect on the critical current capability is evaluated. The magnetic field is computed numerically using the finite element (FE) method. The FE model used for the analysis is described along with the assumptions made. The results indicate that the iron-clad MgB/sub 2/ tapes are undesirable for SC coils in many practical applications from a steady state performance stand point.