Second harmonic in the voltage of dc-carrying YBCO tape under a perpendicular alternating magnetic field

Abstract When a type-II superconductor, exposed to a perpendicular alternating magnetic field, carries a direct current, a biased dc voltage response can occur. The response voltage can be classified into dynamic-resistance voltage and flux flow voltage according to its triggering mechanism. Experimental results for the phase differences of the two types of voltage have been provided in the paper. Harmonic analysis on the voltage response has been carried out to differentiate the two types of the response voltages. Based on analyzing the experimental data, a useful and flexible real-time method using the ratio of the dc component to the second harmonic component of the voltage response has been proposed to serve as a monitor indicating the state of dc-carrying HTS tapes subject to an ac magnetic field. The method is promising in the application of complex superconducting systems such as flux pumps, persistent current switches, superconducting cables and dc fault current limiters.