High-temperature-superconducting machines - A high-technology step for large rotating electric machines

The presently available high temperature superconducting materials (HTS) transport electric current at high current densities with negligible electric losses. This makes it possible to create higher-magnetic fields. Using these features in a rotating electric machine it is possible to reduce the over-all dimensions and weight of the machine, to increase the efficiency and to improve additional features of the machine. To address these goals Siemens started three R&D projects to develop, manufacture and test electric machines with high temperature superconducting field windings. A 400 kW synchronous motor was followed up by a 4000 kVA high speed generator. A 4000 kW high-torque motor will be the third step. Additional to the application in electric machines it is possible to use the substantial advantages of high temperature superconducting materials for passive magnetic bearings. These are operating without any control device of the magnetic field. Siemens started the development of heavy load HTS bearings in parallel to the development of HTS machines.