Self-field AC power dissipation in high-TC superconducting tapes and a prototype cable

Abstract

The measured self-field AC power dissipation in superconducting BiSrCaCuO-2223/Ag tapes and a prototype cable is compared with theoretical models. A brief overview of the theoretical background for AC loss calculations in superconductor tapes with different geometrical shapes is given. New models for the harmonic components of the fundamental frequency and the current dependent nonlinear inductance are also derived. It is shown that the latter models can be used to estimate current distribution and the variation of flux penetration in superconducting tapes. Two separate experimental apparatus were designed and constructed for measurements on tapes and prototype cable systems. The observed losses in tapes are reasonably well described by models based on the critical state model. In contrast, the measured losses in the prototype cable are found to be a factor of approximately two higher than the predicted values. Further investigations showed that this may be due to inhomogeneous contact resistance between individual tapes and the current joints and the variation in critical current density distribution between tapes. The significance of current dependence of the loss component, inductive quadrature component, phase error in measurements and the definition of the critical current in the prototype cable are also discussed.