High temperature superconducting demonstration synchronous generator with a coreless rotor: design, build and test

In the past couple of years significant funding has been directed in the USA towards applications of high temperature superconductivity for electric motors and generators, especially in naval applications. In the UK we are the only group which can claim significant advances in this promising technology for power applications. We propose to build on our achievements under the previous grant GR/N21253/01, and benefit from the dramatic improvements in the technology of HTS tapes, by designing and building a coreless rotor (using the same stator). Preliminary estimates based on careful field modelling suggest that savings in weight of the rotor of at least 60% should be expected and we are confident, as in the previous design, that we can achieve necessary fields using liquid nitrogen or air cooling (at 64K) without the need to reduce the temperatures to 25-30K, which is the standard approach in other designs but which reduces significantly cryogenic efficiency. The coreless design / which is the ultimate goal in the design of HTS machines / will be possible thanks to our innovative use of flux diverters which protect BSCCO tapes from excessive fields; such diverters will not be necessary when superconductors with better field performance become available. We consider the HTS technology to have matured to the level that that the next generation demonstrators, like the one suggested in this proposal, can be attempted.