Last month, Siemens’ Research Centre at Erlangen in Germany started up the first motor in Europe with a winding made of high-temperature, superconducting material.
High-temperature superconductors can carry high-density current with virtually no loss. Power output is more than double that of conventional motors of a similar size made with copper windings, while losses are halved.
Suitable applications for the compact, superconductor motor are mainly those which call for space- and energy-saving, such as on ships or oil platforms. The technology is also suitable for gas turbines, making it possible to build high-speed generators which can be coupled directly to a turbine without the need for a gear box.
Until recently, it has been necessary to reduce temperatures to minus 273 degrees Celsius, just above absolute zero, in order to obtain a superconducting effect from a superconducting material. This required the use of liquid helium, which is very time-consuming and costly to manufacture.
With high-temperature superconductors, however, such an effect can be obtained at around minus 190 degrees Celsius. The higher transition temperature significantly reduces the cooling effort required, thereby making superconductor technology an economically viable proposition.
There are also advantages for the entire mechanical structure of the drive. For instance, the rotor can be smaller than one in a conventional motor. And even the iron teeth which conduct the magnetic field in conventional motors become superfluous. The result is a saving in weight and volume combined with lower noise emission.
The high-temperature superconduction technology is currently being tested with a trial motor. The rotor with superconducting coils is mounted in a motor housing with an air-gap stator winding. The rotor is cooled in a closed circuit system. During experimental operation in motor and generator modes the trial motor has reached a continuous power output of 400 kilowatts.
The project was sponsored by the Federal German Ministry for Education and Research (BMBF).