Generation of higher harmonics in voltage on superconducting wire carrying cosine-like AC current

Abstract

Hard superconductors are known to exhibit nonlinear and hysteretic magnetic properties. Then, the electrical field on the surface of a wire made from such material carrying AC current, will be nonharmonic also in the case when the excitation current is purely cosine-like. We show the harmonic spectra of this signal computed in both numerical and analytical way, following the critical state model with constant j/sub c/. Odd harmonics only are present in the signal. Assuming the cosine-like transport current, the sine components are negligible in wide range of current amplitudes, except the fundamental sine component. The ratio between harmonic components remains constant up to the current amplitudes close to the critical current. Theoretical results are compared with experiments carried out on two samples: multifilamentary tape from HTS Bi-2223 in metallic matrix, and sintered tubes of Bi-2223. Measured content of higher harmonics laid below theoretical results for both the samples, indicating that the simple model with constant j/sub c/ does not sufficiently describe the flux pinning in these materials.