INDUCED CURRENT IN A BI2SR2CACU2OX SUPERCONDUCTOR TUBE

Experiments were conducted to measure the induced current in a high-te mperature Bi2Sr2CaCu2Ox superconductor tube that was excited by an ext ernal coil driven by an AC sinusoidal voltage source. Experimental dat a were obtained for tests without and with an iron core inside the sup erconductor tube. All of the tests were conducted at 77 K and an excit ation frequency of 60 Hz. The results showed that immediately after fi eld penetration, the induced current (RMS value) decreased from the cr itical current, then began to recover, and eventually approached the c ritical current again at a high excitation current. Before field penet ration, the induced current was mainly shielding current, which is 180 degrees out of phase with the excitation current. After field penetra tion, the induced current consisted of two parts, a shielding current that led the excitation current by 180 degrees and an inductive curren t (Faraday's law) that led the excitation current by 90 degrees. The p resence of the iron core amplified the drop in induced current immedia tely after field penetration and delayed the growth of the inductive c urrent after field penetration. Published by Elsevier Science Ltd.