5MW super motor passes tests; 36MW version on the way

A prototype 5MW high-temperature superconductor (HTS) motor has successfully completed an initial test programme conducted by the US Navy to determine the suitability of the technology for ship propulsion.

During the tests, the 5MW machine (below) - designed and built jointly by American Superconductor (AMSC) and by Alstom Power Conversion in the UK - was operated at full-speed (230 rpm) for 21 hours and achieved a steady temperature in both the stator and rotor. It was also subjected to torque variations of up to 10%, to simulate conditions in a moderately strong sea.

AMSC is now building a 36.5MW motor with Northrop Grumman, which is due to be delivered to the US Navy for testing next year. This machine will be powerful enough to propel a ship.

HTS motors could be one third of the weight and half the size of conventional copper-based motors of a similar power and torque rating. This would create much more room for passengers and cargo on board ships. They are also expected to be more efficient and to need less maintenance

AMSC designed and built the HTS rotor and the cryogenic refrigeration for the 5MW motor, while Alstom designed and built the stator and drive electronics.

American Superconductor`s chief executive Greg Yurek expects to announce the first commercial customer for a marine HTS motor during 2006.

• Rockwell Automation has demonstrated the first HTS motor to use second-generation HTS wires and coils, which should be cheaper to produce and to keep cool than first-generation wires. The 1.5kW Reliance Electric motor contains 14m of the ceramic-based wire which remains superconducting at liquid nitrogen temperatures (-196°C). First-generation wires need to be cooled about 40 degrees further, using more costly media such as liquid helium.