FREQUENCY DEPENDENCES OF AC LOSSES IN (BI1-XPBX)SR2CA2CU3OY BULK SUPERCONDUCTORS IN AC MAGNETIC-FIELD

It is shown that the observed ac loss in a cylindrical (Bi1-xPbx)(2)Sr2Ca2Cu3Oy (Bi-2223) bulk superconductor with the diameter of 9.6mm in the ac magnetic field depends on the frequency of ac field contradicting the conventional theory based on the critical state model. The numerical simulation of electromagnetic field was performed by solving the Maxwell equations using the observed magnetic field dependence of critical current density and voltage-current characteristics. As the results, it is clarified that this deviation originates from the fact that the internal distribution of flux density is different from that predicted by the critical state model.