Electric field in Bi-2223 tape carrying DC current and exposed to AC parallel magnetic field

A study of the degradation of the critical current of Bi-2223 tapes under AC magnetic fields is of great importance for HTS power applications. In particular, in a common AC coil design, the field component parallel to plane of the tape is much stronger than the perpendicular component. In this work we present the results of electric field measurements of Bi-2223 tape exposed to AC magnetic field parallel to the broad side of the tape with various frequencies and amplitudes. The observed E-I curves can be described as an additional voltage to the E-I curve superimposed on the zero-field curve. This additional voltage increases with amplitude and frequency of the AC magnetic field and grows almost linearly with DC current, peaks close to the zero-field critical current and decreases thereafter. We analyzed the correlation of the electric field with indicated parameters on the base of the theoretical predictions of H. Brandt and G Mikitik and found a striking agreement of the calculated and observed values. Measurements of the time dependent electric field exhibit double-frequency features and strong dependence of the electric field on the amplitude and frequency of the AC magnetic field.