1,659 research outputs found
Field and current distributions and ac losses in a bifilar stack of superconducting strips
In this paper I first analytically calculate the magnetic-field and
sheet-current distributions generated in an infinite stack of thin
superconducting strips of thickness d, width 2a >> d, and arbitrary separation
D when adjacent strips carry net current of magnitude I in opposite directions.
Each strip is assumed to have uniform critical current density Jc, critical
sheet-current density Kc = Jc d, and critical current Ic = 2a Kc, and the
distribution of the current density within each strip is assumed to obey
critical-state theory. I then derive expressions for the ac losses due to
magnetic-flux penetration both from the strip edges and from the top and bottom
of each strip, and I express the results in terms of integrals involving the
perpendicular and parallel components of the magnetic field. After numerically
evaluating the ac losses for typical dimensions, I present analytic expressions
from which the losses can be estimated.Comment: 8 pages, 9 figure
Hysteretic ac loss of superconducting strips simultaneously exposed to ac transport current and phase-different ac magnetic field
A simple analytical expression is presented for hysteretic ac loss of a
superconducting strip simultaneously exposed to an ac transport current
and a phase-different ac magnetic field . On the basis of Bean's critical state model, we calculate for
small current amplitude , for small magnetic field amplitude
, and for arbitrary phase difference , where
is the critical current and is the width of the strip. The resulting
expression for is a simple biquadratic function of both
and , and becomes maximum (minimum) when or
().Comment: 4 pages, 2 figures, submitted to Appl. Phys. Let
Inductive measurements of third-harmonic voltage and critical current density in bulk superconductors
We propose an inductive method to measure critical current density in
bulk superconductors. In this method, an ac magnetic field is generated by a
drive current flowing in a small coil mounted just above the flat surface
of superconductors, and the third-harmonic voltage induced in the coil is
detected. We present theoretical calculation based on the critical state model
for the ac response of bulk superconductors, and we show that the
third-harmonic voltage detected in the inductive measurements is expressed as
, where is the frequency of the drive
current, and is a factor determined by the configuration of the coil. We
measured the - curves of a melt-textured
bulk sample, and evaluated the by using the theoretical results.Comment: 3 pages, 1 figure, submitted to Appl. Phys. Let
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