Field-free core, current distribution, and alternating current losses in self fields for rectangular superconductor tapes

A method is proposed to calculate the shape of field-free core, the current distribution, and accordingly the alternating current (ac) losses in self fields as a parameter of current amplitude Io for straight superconductor tapes with the arbitrary sectional geometry. The validity for this is justified by showing that magnetic fields inside the field-foe core are negligibly small and by checking that calculation results of ac losses for elliptic tapes agree with the prediction by the theory of Norris. The ac losses for rectangular tapes behave as a thin strip superconductor in high Io values near critical current, while showing a gradual deviation from this behavior as Io is lowered. A decrease in the aspect ratio of width to thickness in the rectangular tape makes the deviation more remarkable. (C) 1998 American Institute of Physics. [S0003-6951(98)02425-5].