Basic concepts, status, opportunities, and challenges of electrical machines utilizing high-temperature superconducting (HTS) windings

An overview of the different approaches towards achieving a marketable application of a superconducting electrical machine, either as synchronous motor or generator, will be given. This field ranges from relatively small industrial drives to utility generators with large power ratings, from the low speed and high torque of wind power generators and ship propulsion motors, to high speed generators attached to turbines. Essentially HTS machine technology offers several advantages such as compactness (weight and volume reduction), increased efficiency, and other operational benefits. The machine features have to be optimized with regard to the specific application, and different concepts were developed by internationally competing teams, with Siemens being one of them. The achieved status in these fields will be summarized, pointing to the specific technical challenges to overcome. For this purpose we have not only to consider the technology of manufacturing the HTS rotor winding itself, but also to check requirements and availability of supporting technologies. This ranges from new challenges posed to the non-superconducting ("conventional") components of such innovative HTS machines, manufacturing superconducting material in the coming transition from 1st to 2nd generation HTS tape, cryogenic technology including material behavior, to new and challenging tasks in simulating and predicting the performance of such machines by computational tools. The question of market opportunities for this technology obviously is a function of all these aspects; however, a strong tendency for the near future is seen in the area of high-torque ship propulsion.