AC loss characteristics of twisted multifilament Bi2223/Ag sheathed tapes carrying AC transport currents in AC longitudinal magnetic fields

摘要

This paper reports on the total AC loss characteristics of a twisted multifilamentary Bi2223/Ag sheathed tape carrying AC transport current in longitudinal AC magnetic field in phase with the transport current. The tape was specially made for the experiment and had wider space between superconducting filaments than a usual multifilamentary Bi/Ag sheathed tape to suppress superconducting bridgings between the filaments. In our experiment the total losses were measured by the electric method. The losses supplied from the longitudinal magnetic field were measured by using a pick-up coil and the losses supplied from the power supply for the transport current by a four terminal method. The measurement results showed that the total losses depended on the direction of the longitudinal magnetic field. In the case that the combined magnetic field produced by the transport current and the external longitudinal magnetic field was nearly parallel to the filaments of the twisted wire, the losses were smaller than those in the case that the combined field was nearly perpendicular to the filaments. This was observed when the amplitude of the longitudinal magnetic field was larger than the full penetration magnetic field of the wire.