AC loss and dynamic resistance of a high T(sub c) strand carrying a direct current in a transverse AC magnetic field
Abstract
A superconducting wire (diameter, d) exposed to an AC longitudinal or transverse magnetic field (amplitude, H(sub m)) experiences a hysteretic power loss, W(sub h). If a DC transport current (density, J) is next applied, extra dissipation is encountered as the current interacts with the moving mixedstate vortices. But if J and H(sub m) are sufficiently small, and J(sub c) and d sufficiently large it is possible for lossfree current to flow down the central core of the wire out of range of the oscillating field. In other words, H(sub m) should be less than some 'penetration value,' H*(J) = H*(1j), where H* is the usual penetration field and j is equivalent to J/J(sub c). The currentrelated dissipation, W(sub dyn), can be interpreted as taking place within a dynamic resistivity, rho(sub dyn). Below H*(J) the only dissipation is W(sub h); above it the dissipation is W(sub t) = W(sub h) + W(sub dyn). In the latter regime, as J increases W(sub h) decreases and W(sub dyn), increases. The result is a net increase in W(sub t) during which, as J approaches J(sub c), W(sub h) tends to zero and W(sub dyn) undergoes a smooth transition to the fluxflow (and eventually, normal) state. Some of these predictions were confirmed in a series of studies of dynamic resistivity in two samples of high(Tc) YBCO stranda lowJ(sub c) braid and a highJ(sub c) monofilamentpassing DC transport currents in transverse AC fields with H(sub m)s of up to about 800 gauss. Also described are the results of hysteresis loss measurements, taken at J = 0 using vibratingsample magnetometry.
 Publication:

Presented at the Cryogenic Engineering Conference and International Cryogenic Materials Conference
 Pub Date:
 1991
 Bibcode:
 1991cren.conf...11C
 Keywords:

 Alternating Current;
 Current Density;
 Direct Current;
 Electrical Resistivity;
 High Temperature Superconductors;
 Superconductivity;
 Wire;
 Electric Fields;
 Hysteresis;
 Magnetic Fields;
 Magnetic Measurement;
 Oscillations;
 Electronics and Electrical Engineering