Abstract
In our previous paper, we proposed a new indirect method of detecting normal transitions occurring in hightemperature superconducting coils. In this method, sets of pick-up coil pairs arranged outside the cryostat are used in order to electrically measure the occurrence of normal transitions during coil operations. This indirect method has benefits such as high reliability, safe detection and easy maintenance. The principle of locally detecting a normal transition is theoretically explained and the validity of this method is clarified experimentally using a Bi-2223 coil. In this paper, it is experimentally confirmed that this measuring method can be used to detect normal transitions in windings of a high-temperature superconducting transformer with 500 VA around which there are small leakage magnetic fields due to an iron core. In addition, a method for detecting normal transitions in windings of the transformer during transformer load changes is proposed and the validity of the method is demonstrated experimentally.
