AC Loss Measurements at High B, dB/dt for ReBCO Tape Stacks With Various Values of Tape Separation and Loss in Helically Wound Cables

Abstract

The demand for high-power motors and generators for electric aircraft requires conductors with performance above that of ambient temperature Cu and Al. High current density superconducting Re-Ba-Cu-O (ReBCO) conductors and cables are of interest, but AC loss characterization under relevant excitation is needed. In this work, we explored the AC losses of ReBCO tapes, tape stacks, and round (CORC) cables at aircraft motor/generator relevant fields and frequencies. The measurements were performed using a previously described Spinning-Magnet-Calorimeter (SMC), where a superconducting sample is placed in an LN₂ bath and exposed to the magnetic fields of a spinning magnetic Halbach array. In this system, loss is measured using a calorimetric method (measuring the LN₂ boil off). Previous work has shown a significant shielding effect with higher numbers of ReBCO tapes in a stack. This present work looks at the reduction of this shielding with increased tape-to-tape separation distance in stacked tape samples. This work also explored loss in CORC cables with different numbers of layers, and compared the loss per tapes for CORC conductors with different numbers of layers (and with both striated and unstriated tapes). The magnitude of the shielding as a function of layers is compared for the two conductors.