Effect of soft ferromagnetic substrate on ac loss in 2G HTS power transmission cables consisting of coated conductors

Abstract

As a model of second-generation high-temperature superconducting (2G HTS) power transmission cable, the effect of soft ferromagnetic (FM) substrate on hysteretic ac loss in a round cable carrying transport current or exposed to radial magnetic field is investigated theoretically. We consider the FM substrates as ideal soft magnets with an infinite permeability, neglecting the magnetic hysteresis. The analytical expressions of field and current distribution around a curved superconductor tape with FM substrate were derived applying the complex-field approach. FM components can strongly influence the ac loss behaviors in a round cable composed of coated conductors. The approximate expressions for ac loss in a round cable at small currents or low fields are obtained. It is shown that at small currents the ac loss QFM in a round cable for FM substrate depended on ac current amplitude ia and central angle θn as , while at low fields ha , the order of which differs significantly from QNM for nonmagnetic (NM) substrate. Additionally, the influence of the central angle as well as tape-width of coated conductors on the ac loss characteristic in a round cable is discussed. The ac loss QFM can be reduced by a suitable tape-width of coated conductor at higher fields as compared with QNM.