Losses in Bi-2223/Ag tape at simultaneous action of AC transport and AC magnetic field shifted in phase

Abstract

Investigation of AC loss under simultaneous action of transport AC and external AC field is of prime importance for reliable prediction of dissipation in electric power devices like motors/generators, transformers and transmission cables. The experimental rig allowing to perform AC loss measurement in such conditions on short (10 cm) samples of tapes from hightemperature superconductor Bi-2223/Ag has been designed and tested. Both the electrical and thermal method have been incorporated, allowing to combine better sensitivity of former one and a higher reliability of the latter one. Our main aim is to see how the AC loss depends on the phase shift between the current and the field. Such a shift could acquire rather different values in various applications. While in transformer winding, the maximum phase shift at full load will probably not exceed a few degrees, in a three phases transmission cable in tri-axial configuration it is around 120°. Therefore we explored the whole range of phase shifts from 0 to 360°. Surprisingly, the maxima of dissipation do not coincide with zero shift as expected from qualitative considerations. © 2006 IOP Publishing Ltd.