Influence of the voltage taps position on the self-field DC and AC transport characterization of HTS superconducting tapes

TL;DR

This paper investigates how the position of voltage taps affects the accuracy of DC and AC transport measurements in HTS superconducting tapes, proposing methods to improve measurement reliability and reduce eddy current losses.

Contribution

It demonstrates through simulations and experiments that placing voltage taps outside the active area yields equivalent results to standard methods and offers better protection insights, also addressing AC loss measurement challenges.

Findings

External voltage tap placement provides reliable I-V measurements.

Simulation confirms eddy current loss contribution can be minimized.

Optimized current leads reduce AC loss due to eddy currents.

Abstract

The current-voltage (I-V) curve is the basic characteristic of a superconducting wire or tape. Measuring I-V curves is generally problematic when samples have poor stabilization. Soldering voltage taps to an active part of the conductor affects the effectiveness of the local cooling and/or can be difficult to do in certain devices such as fault current limiters and cables where the tapes are closely packed. In order to overcome these problems, voltage taps can be placed outside the active area of the superconductor. We proved both by simulations and experiments that this arrangement leads to the same results as the standard four point method and it provides more detailed information for sample protection. The same arrangement can also be used for AC transport loss measurement. However in this case particular care has to be taken because the eddy current loss in the current leads contributes to the total measured loss. We used numerical simulations to evaluate the contribution of the eddy current loss to the measured AC loss. With help of simulations one can determine whether the contribution of the eddy current loss is significant and possibly optimize the current leads to reduce that loss contribution.