Study of ac loss in Bi-2223/Ag tape under the simultaneous action of ac transport current and ac magnetic field shifted in phase

Abstract

Investigation of ac loss under the simultaneous action of the transport ac current and the external ac magnetic field is of prime importance for the reliable prediction of dissipation in electric power devices such as motors/generators, transformers and transmission cables. An experimental rig allowing us to perform ac loss measurements in such conditions, on short (10 cm) tape samples of high-temperature superconductor Bi-2223/Ag, was designed and tested. Both the electromagnetic and thermal methods were incorporated, allowing us to combine the better sensitivity of the former and the higher reliability of the latter. Our main aim was to see how the ac loss depends on the phase shift between the transport current and the external magnetic field. Such a shift could have different values in various applications. While in a transformer winding, the maximum phase shift at full load will probably not exceed a few degrees, in a three phase 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 did not coincide with zero shift as expected from qualitative considerations.

Computation of Losses in HTS Under the Action of Varying Magnetic Fields and Currents

“…4) AC losses from the point of view of the power source: By continuity of the energy flow, the loss per cycle dissipated in the superconductor equals the energy per cycle supplied by the current sources. In general, a superconductor may be under the effect of a transport current or a magnetic field created by an external winding, which implies two current sources [74], [75].…”

Hysteretic ac loss of superconducting strips simultaneously exposed to ac transport current and phase-different ac magnetic field

“…Note that the experimental Q can be maximum ͑minimum͒ when 0 0 ͑ 0 /2͒, as reported in Refs. [17][18][19]. The reason for the shifts in 0 for maximum and minimum Q is that the ac magnetic field was large ͑i.e., h 0 Ͼ 1͒ in those measurements.…”

Study of Critical Current and n-Values of 2G HTS Tapes: Their Magnetic Field-Angular Dependence

“…In addition, the cost of devices can be further reduced by X. Zhang xz326@cam.ac.uk 1 Department of Engineering, University of Cambridge, Cambridge CB3 0FA, UK optimizing the layout and also minimizing the quantity of YBCO-coated conductors that is required by an apparatus. This optimization process needs information of the magnetic field-angular dependence of critical current density J c (B, θ) [7].…”