Several AC power applications of YBCO-coated conductors (CCs) involve superconducting
tapes wound in coils. In such a configuration the superconducting tape is arranged as
closely packed turns, which strongly interact due to the generated magnetic field. This has
a strong influence on the AC losses, which are different from those of an isolated tape, and
need to be precisely quantified in order to predict and reduce the refrigeration requirements
of applications. In this paper we experimentally evaluate the transport AC losses in a
pancake coil composed of 25 turns of superconducting tape. We describe in detail the
measuring technique utilized, pointing out the issues in this kind of measurement.
We also present preliminary results of AC loss computation by finite-element
modelling.
This paper presents a new finite-element simulation model for computing the electromagnetic properties and AC losses in systems of YBCO (yttrium barium copper oxide) conductors on roll assisted biaxially textured substrates (RABiTS). In this model, the magnetic field dependent permeability and ferromagnetic loss of the substrates in RABiTS YBCO tapes are taken into account. The simulations were employed to simulate the AC loss in stacks of two parallel connected YBCO tapes. The simulation results are compared with the experimental data to check the validity of the simulation model. The result reveals an effective way of significantly reducing AC loss in YBCO tapes by stacking two RABiTS YBCO coated conductors with the appropriate relative tape orientation.
Some applications of high temperature superconducting conductors require a non-inductive winding, which may be constructed from antiparallel connected YBCO (yttrium barium copper oxide) tapes. In the case of AC applications, this antiparallel winding changes the AC losses from that of an isolated conductor. This study focuses on the effect of the spatial separation and misalignment between conductors on their AC loss behavior for YBCO conductors on both rolling assisted biaxially textured substrate (RABiTS) and ion beam assisted deposition templates in an effort to fully understand the behavior of these conductors in real world applications. For RABiTS samples, the study was carried out for all three possible configurations (the so-called back-to-back, front-to-front and same-way configurations) to clarify the effect of the ferromagnetic substrate on the AC loss behavior in these conductor configurations. Numerical simulations were also employed in some cases to compare with and elucidate experimental observations.
This paper presents a quantitative comparison of the AC loss performance of two BSCCO
and two YBCO conductors, characterized by the same self-field critical current of 150 A. We
compare a 37-filamentary BSCCO tape, a 16-filamentary BSCCO square wire, a standard
YBCO tape, and a stack of four narrower YBCO tapes. The comparison is made using a
numerical technique, based on the finite-element method, which employs a non-linear
E–J
relation and a dependence of the local critical current density
Jc
on the local magnetic field. For the simulation of YBCO conductors, a new ‘shell-region’
model is utilized. This overcomes the geometry and mesh problems typical of
superconductors with very high geometric aspect ratio. Different AC working conditions are
simulated: self-field, applied external field, and combined transport current and external
field of varying orientation. We outline the advantages of using BSCCO or YBCO
conductors for the different applications. Various magnetic field and current density profiles
are investigated in order to illustrate the reasons for the loss difference in the four
conductors. Particular attention is drawn to the YBCO tape and the YBCO stack, whose
AC loss characteristics are less well known than those of BSCCO conductors.
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