Fabrication and test of superconducting air-core autotransformer

An experimental superconducting air-core autotransformer (SCACAT) with a rating of 2.5 kVA was fabricated. The configuration of the autotransformer is adopted because it is appropriate for air-core transformers to mitigate the increase of the impedance. The rated voltage and current are 300/150 V and 14/17 A, respectively. The current ratio does not coincide with the inverse of the voltage ratio because of the presence of the large exciting current. No-load, short circuit, and load tests were carried out. The experimental results indicate that, as expected, the exciting current becomes very large. It occupies about 45% of the rated current. In addition, the leakage impedance increases considerably; it becomes about 0.28 pu