Study of 6 MVA superconducting generator

In the field of electric machinery, the superconduction in generators has been noticed as it has the highest possibility of realization, and the many tests on the trial manufacture have been carried out. In case of applying the superconduction technique to generators, superconducting wires are used for magnetic field windings. Superconducting wires cause alternating current loss such as hysteresis loss, therefore it is not advantageous to use superconducting wires for armature windings through which alternating current flows. In case of applying superconduction to field windings, new techniques must be applied to cool rotors rotating at high speed down to extremely low temperature. High efficiency can be expected even when the power required for cooling is added, because there is no exciting loss in windings. Very high magnetic field can be generated with superconducting field windings without using iron cores, and electric loading can be made large, therefore the weight and size of generators can be reduced to 1/2 or 1/3 as compared with conventional ones. Fuji Electric Co., Ltd. has manufactured a 30 KVA superconducting generator before, and this time, succeeded to manufacture a 6,250 KVA superconducting generator after 3 year research. The basic construction of this generator, the rotor cooled with liquid helium, the stator, and the results of the test operation are described. (Kako, I.)