AC losses in long Bi-2223 tapes wound into a solenoidal-coil

摘要

Electrical loss-measurements were carried out in liquid nitrogen for long Bi-2223 tapes wound into a solenoidal-coil under various external conditions of ac transport currents and ac magnetic fields. In this experiment a new measuring-system, which is an extension of our original measuring-system applicable to short and straight HTS tapes, was developed. In this new system, the Poynting vectors at the outer and the inner surfaces of the sample coil were measured to get ac loss values by using two movable sets consisting of both a potential lead pair and a pick-up coil on each surface of the coil; The moving direction is the coil axis and its distance is one pitch of coil windings. Several samples were prepared in order to clarify fundamental electromagnetic-properties of Bi-2223 coils with various windings. The obvious difference of loss properties among these samples was observed for some external conditions of ac transport currents and ac magnetic fields.