Superconducting transformer failure: Testing and investigation

A partial core superconducting transformer, that was built in the Electrical and Computer Engineering Department, was tested under no-load, short-circuit, full-load and a two minute full-load endurance run. The first no-load, short-circuit and full load tests were only partially successful because the accuracy of the meters were not satisfactory enough to confirm the mathematical models. The transformer failed the endurance run; voltage dipping and rapid liquid nitrogen boil-off was observed one minute and a half into the test. An investigative approach was taken to determine the cause of the failure. The radial field at ends of the partial core, was determined not to have caused the tape to go out of its superconducting state. An open circuit test was performed on one of the outside winding which led to the discovery of a shorted turn. The windings and insulation of the transformer were taken apart to visually observe the faulty turns.