Development of a coreless HTS synchronous generator operating at sub-cooled liquid nitrogen temperatures

This paper presents the current design concepts for a 100kW high temperature superconducting synchronous generator currently being designed at the University of Southampton, UK. The new generator will use the same conventional 2-pole 3-phase stator that was used in the HTS synchronous generator previously constructed at Southampton. The windings consist of 18 pancake coils made from BiPb2223 superconducting tape with a nominal current of 180A at 77K, provided by Sumitomo Electric Industries, Ltd. Tests were performed to determine the mechanical strain limits of the tape. The rotor has no central core, but magnetic pole pieces are used to improve the waveform of the generator. The coils are separated by magnetic diverter rings to reduce the normal field in the tape. The coils and diverter rings are supported by fibreglass formers that extend to the centre of the rotor so that they can be located by the through bolts that hold the stack together. A stainless steel tube encapsulates the rotor to provide a chamber for liquid nitrogen to flood the rotor.