This paper presents the results of my experiments that may open a new path for advanced applications by using continuous closed superconducting YBCO loops. I examined a novel arrangement of a perfectly closed superconducting loop made of HTS wire in DC and AC flux transformer. I designed a self-limiting transformer with this solution. At the same time I also tested the operation of the continuous YBCO loop developed with my own technology. In the first experiment I used YBCO superconducting rings made from a bulk. Later I used superconducting wire. I could carry out these experiments because earlier I had elaborated the machining of the YBCO bulk and wire.