Super motor becomes a variable speed drive

Europe`s first high-temperature superconducting motor has begun to operate as a speed-controlled drive following the installation of a converter section. Until now, the synchronous motor, which has been under test for a year at Siemens` Erlangen research centre, has been tested on the mains as a generator as well as a motor.

Originally, an auxiliary drive was needed to start the machine, but using the converter, it is now possible to run up the motor from a standstill at variable frequencies.

Test results so far have met or exceeded the motor`s design specifications. For example, its designed rating was 380kW, but it has produced a continuous output of 450kW - and as much as 600kW for short periods. It has also shown that it can cope with large variations in load. The rotor, with its HTS windings, has proved itself capable of handling overloads.

Although the motor was not optimised for efficiency, its losses are lower than those of a conventional motor of a similar rating, even when the cryogenic cooling system is taken into account.

Superconducting motors and generators could be a quarter of the size of conventional machines. Potential applications include lightweight ship propulsion systems, variable speed drives for industry, wind-driven generators, and high-speed machines which could be coupled directly to a gas turbine without needing a gearbox.

Siemens` research into HTS machines is being sponsored by the German ministry of research and education.