Siemens recently became the first manufacturer in Europe to start up a high-temperature superconductor (HTS) motor at its Research Center in Erlangen, Germany. Sponsored by the Federal German Ministry for Education and Research (BMBF), this project involves testing high-temperature superconduction technology with a trial motor. The rotor (with superconducting coils) is mounted in a motor housing with an air-gap stator winding. Then, it is cooled in a closed circuit system. During experimental operation in motor and generator modes, the trial motor reached a continuous power output of 400kW, which is equivalent to about 550 hp.
Why commercialize this technology? According to American Superconductor, Westborough, Mass., high-temperature superconductors can carry high-density current with virtually no loss. Power output is more than double that of conventional motors of similar size with copper windings, while losses are halved. Suitable applications for the compact, superconductor motor include those calling for space- and energy-saving machines, such as ships or oil platforms. The technology is also suitable for gas turbines, making it possible to build extremely high-speed generators, which can be coupled directly to a turbine without the need for a gear box. Below the transition temperature, the electrical resistance of superconducting materials disappears. Until now, it has been necessary to reduce temperatures to –273°C, just above absolute zero, to obtain the superconducting effect. This required the use of liquid helium, which is very time-consuming and costly.
With high-temperature superconductors, electrical resistance disappears at around –190°C. This enables virtually loss-free current conduction with a considerably lower line diameter, greater efficiency, and higher magnetic field strength.
According to American Superconductor, Siemens’ progress on HTS motors is good news for the industry. Along with the 1,600 hp HTS motor demonstrated by Rockwell and American Superconductor last year, and the 5,000 hp HTS motor demonstrated by AMSC in July, it points to the momentum developing in the creation of a market for HTS motors and generators and HTS wire sales.
