Transport AC Loss Measurements of a Triangular Epoxy-Impregnated High-Temperature Superconducting Coil

In this paper, the transport ac losses in a triangular epoxy-impregnated high-temperature superconducting (HTS) coil made from YBCO coated conductor, intended for use in a prototype axial flux HTS electric machine, are measured using two different electrical techniques at 77 K. The first set of ac loss measurements of the coil are carried out at the University of Cambridge using a technique based on a lock-in amplifier. The coil is then measured at the Center for Advanced Power Systems, Florida State University, using a technique based on a high-accuracy data acquisition measurement system. The two different methods show consistent results, validating the accuracy of these two techniques for transport ac loss measurements of superconducting coils. Multiple voltage taps are utilized within the coil to study the details and distribution of the ac loss in different sections of the coil. Losses are also measured with a flux diverter made of ferromagnetic material to analyze its effect on the ac losses.