AC loss measurements of parallel-stacked ReBCO coils cooled by a helium gas circulation system

Abstract Transport AC loss measurement results are presented in this paper for a double pancake superconducting coil wound from two parallel ReBCO tapes stacked together and cooled by gaseous helium, between 35 K–45 K. The power dissipation is obtained using an electrical method that involves adjusting a compensation coil to cancel out the inductive component of the voltage measured across the superconducting coil; the current through the coil is measured by a resistive shunt. Three data processing techniques from the literature to calculate the average power dissipation are compared: the first method multiplies the rms values of the compensated voltage and current waveforms (when the waveforms are in phase), the second method further multiplies the rms values with the cosine of the phase difference between the compensated voltage and current, and the third method integrates the waveform which is the product of the compensated voltage and current waveforms (followed by division by the time period). It is found that the second and third methods give power dissipation that is unchanged over a wider range of compensation, thus the compensation coil can be adjusted less precisely compared to the first method, reducing the time needed for manual adjustment during the measurement process.