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A continuous disk winding (CDW) technique for high voltage High Temperature Superconducting (HTS) transformers is discussed. Findings reveal that CDW technique is advantageous as it offers good insulation, limitation of voltage stress and low AC losses.

An in-situ measurement of the magnetic field generated by the assembled superconducting magnet coils was held by using precision Hall sensors during the commissioning of the Korea Superconducting Tokamak Advanced Research (KSTAR) device. This was done in order to investigate the magnetic influence of Incoloy 908, which is the jacket material for the cable-in-conduit conductors (CICCs) of the Nb3 Sn coils. After the PF coils were discharged from 1 kA the vertical remanent field at the plasma center was more than 10 G, while the TF coils were not energized. The vertical magnetic field generated by the PF coils had a discrepancy of up to 50 G between measurement and the calculation assuming no magnetic influence of Incoloy 908. Thus, non-negligible ferromagnetism was identified and attributed to Incoloy 908. In contrast, most of the hysteresis observed in the magnetic measurements was eliminated when the Incoloy 908 of the TF windings was saturated by the TF coil charging. [ABSTRACT FROM AUTHOR]

AC loss is an important issue to design high temperature superconductor power cables, which consist of a number of Bi-2223 tapes wound on a former. In the cables, the tapes have intrinsically different critical currents, and they are electrically connected to each other and current leads. This makes loss measurements considerably complex, especially for short samples. In this work, we have prepared a multi-tape conductor composed of Bi-2223 tapes. The ac losses of the conductor have experimentally investigated. The loss tests indicate that the effect of critical currents of each tape on AC loss measurement in the multi-tape conductor is negligible only if currents in the tapes flow uniformly. Moreover, the measured loss of the conductor is in good agreement with the stun of the transport loss in each tape. However, in the case of nonuniform current distribution, the measured AC loss considerably depends on the current distribution parameter γ, and the positioning of a voltage lead. Thus it should be very careful to measure the AC losses in the short power cable samples. [ABSTRACT FROM AUTHOR]

In high temperature superconducting (HTS) transformer with double pancake windings, the perpendicular component of leakage magnetic flux density (Br) applied to HTS tapes of double pancake windings is larger than that of solenoid windings, which acts as a cause to decrease the critical current in HTS tape and increase AC loss. In this paper, in order to reduce the Br applied to HTS windings, the use of ferrite flux diverters is presented. Flux diverters are located in between the primary windings and the secondary windings, and must be made of low-loss materials to minimize the heat. And electromagnetic analysis of a single-phase 1 MVA 22.9 kV/6.6 kV HTS transformer with flux diverters in HTS windings was accomplished. The variation of Br applied to the secondary windings and magnetic flux density in flux diverters were analyzed by changing their relative permeability of flux diverters respectively. Suitable relative permeability of flux diverters to reduce Br applied to HTS windings was selected, considering flux diverter losses by increment of B in flux diverters. [ABSTRACT FROM AUTHOR]