Characteristics Comparison Between HTS Air Core and Partial Core Transformers

This paper presents the characteristics comparison between an HTS air-core transformer (ACT) and an HTS partial-core transformer (PCT) by experiment and simulation. Two types of transformers were fabricated and tested in liquid nitrogen at 77 K. Fundamental characteristics were obtained by no-load, load, and short-circuit tests. The parameters of the equivalent circuits of the two transformers were also obtained. A field-circuit finite-element method was proposed to analyze the electrical characteristics. In addition, the experimental results were compared with the numerically calculated ones. The results show that the measured critical currents of the transformer with and without the iron core are nearly the same. The measured exciting current and percent voltage regulation of the PCT is smaller than that of the ACT. The PCT has a better short-circuit current limiting function. The numerical results show that the uneven degree of circulating current of ACT is larger than that of the PCT. The loss characteristic was also discussed in this paper.