Technology news: April 2006
Superconducting bearing is `world`s first`
At this month`s Hannover Fair, Nexans SuperConductors (NSC) and Siemens demonstrated what they claim is the world`s first superconducting bearing for industrial applications. Siemens commissioned NSC to develop the prototype bearing for a 4MVA superconductor generator that it is building.
The bearing (shown above) uses high-temperature superconductors (HTSs), cooled to temperatures below -210°C, to suspend a rotating shaft in a magnetic field. The prototype can carry a radial load of up to 690kg at speeds of up to 3,600 rpm. The rotor, incorporating permanent magnets, runs in a bore with a gap of just 1mm. Shaft vibrations induced by resonant frequencies are attenuated by an electrodynamic damper.
The rugged HTS bearing is maintenance- and wear-free and, unlike active magnetic bearings, is said to be inherently safe without needing extra sensors or software.
The HTS bearings are expected to open up new applications, and to improve existing ones, in areas such as high-speed drives, generators, and compressors. They could, for example, be incorporated into variable-speed compressors designed to optimise production processes.
Another promising application is for high-speed flywheels which store electrical energy temporarily in the form of rotational energy. When power is needed, the rotating mass drives a generator to feed current back into the power supply. The non-contact HTS bearings will allow these flywheels spin faster, thus boosting their power densities. The bearings would also avoid energy losses caused by friction. NSC expects to have a bearing of this type ready by the end of this year.