Electromagnetic properties of large capacity superconducting cables in a 1000kVA-class superconducting transformer

We have designed and fabricated a 1000 kVA-class power transformers with iron core in a room-temperature space to test the electromagnetic properties of kA-class superconducting cables as the secondary winding. The test cable is a triply-stacked multi-strand (6x6x6) type. The elementary strand has 19,050 NbTi filaments of 0.63 μ m diameter in CuNi matrix. The maximum current of the cable in no-load operation was 5.16 kA(peak). The attained level of the secondary current is 59 % of the critical one on the load line. A higher operation current was achieved by uniforming the current distribution in the multiply-stacked cable and the current transfer between the cable and copper current terminals. In load tests, the capacity of the transformer attained to 577 kVA at the secondary current of 3.00 kA within a restriction of the primary power supply. The structure of the large-capacity cables is also discussed by taking account of an adiabatic stability in longitudinal field.