Dynamic response of HTS composite tapes to pulsed currents

The frequency-dependent critical current of a superconductor strip and Roebel cable has been studied using a 2D finite element simulation. It is shown that the critical current of the superconductor increases with frequency as f 1/n , where n is the exponent of the power law flux creep model. Transport ac loss in a superconductor strip decreases with frequency as f −2/n when the amplitude of the applied ac current is far less than its critical current. However, when the applied current is large and becomes comparable to the critical current, the transport ac loss decreases with frequency as 1/ f . The analytical results are substantiated with available experimental data and the results of a 2D finite element simulation.

Section: Thin Stripmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Frequency-dependent critical current and transport ac loss of superconductor strip and Roebel cable

Thakur¹,

Raj²,

Brandt³

et al. 2011

“…(8) A frequency dependent critical current was introduced by Rhyner [34], and was further developed in [35,36]. Reference [37] has tried several different theoretical approaches to account for the frequency dependence of magnetic susceptibility, and finally ended up using an empirical equation which resembled the π/2 rule [33] for spin-glass systems (χ = −π/2(dχ /d ln(ω))) at some specific magnetic field.…”

Section: Frequency Dependencementioning

confidence: 99%

Frequency dependent magnetization of superconductor strip

Thakur¹,

Raj²,

Brandt³

et al. 2011

The frequency dependence of magnetic ac loss of thin superconductor strip subjected to an ac magnetic field perpendicular to the surface of the strip is investigated by incorporating a flux creep model into the critical state model of Brandt and Indenbom. It is found that the reduced ac loss exhibits a maximum value at a frequency f m , which is a rapidly varying function of the applied ac magnetic field. At low magnetic field, f m becomes zero, and ac loss decreases with frequency as a power law (∼ f −2/n ). Whereas at high magnetic field f m becomes infinite and ac loss increases with frequency, still following the power law (∼ f 1/n ). The analytical results are substantiated with experimental data and the results of a 2D finite element simulation.

“…All the integral equations we proposed in the previous paragraphs cannot be analytically solved and have to be worked out by means of some ad hoc numerical scheme, essentially based on substituting the integrals with finite sums and on transforming the equations in systems of algebraic equations (see, for instance, [16]). Even so, another more practical way can be followed by using a general purpose FE commercial package (in our case COMSOL Multiphysics version 3.4 [17]) that allows implementing parameter-depending integrals.…”

Section: Integral Equations Solutionmentioning

confidence: 99%

AC losses in thin superconductors: the integral equation method applied to stacks and windings

Brambilla

Grilli

Nguyen

et al. 2009

In this paper we present a method for computing transport current ac losses in interacting thin superconductors. The method solves the integral equations for the sheet current density distribution and is specifically developed for those configurations where the symmetry of the current density distributions allows writing the equation in a self-consistent form, without the need for using an auxiliary 2D model to describe the interaction between superconducting tapes. This results in very short computation times and therefore the model can be very useful for optimizing the design of superconducting devices. The method has been tested for different cases of practical applications and the ac loss results have been compared with those obtained with analytical models and with experiments.