U.S. Navy tests large superconductor motor

The U.S. Navy has successfully power-tested a superconducting motor producing 49,000 hp.
Superconducting technology allows for the design of motors that have very high power outputs relative to their size and weight.
The first full-power test of the motor, conducted in January 2009 at the U.S. Navy’s Integrated Power System Land-Based Test Site in Philadelphia, confirmed the 49,000-hp (36.5-megawatt) output.
A pair of these motors could be used to power a large Navy combat ship like the DDG-1000 series destroyers. This motor doubles the Navy’s power-test record for an electric motor of any design.
The motor was jointly developed by Northrop Grumman and American Superconductor Corp. (AMSC).
The new motor uses American Semiconductor’s high temperature superconductor (HTS) technology to achieve very high efficiency by eliminating virtually all resistance to the flow of electrons.
“This motor weighs about 75 tons compared to 300 tons for a tradition copper wound electric motor," said Jason Fredette, director of investor relations for AMSC. “This weight savings is of great interest to the Navy."
This new electric motor technology also has applications for commercial vessels such as LNG tankers and cruise vessels. These types of commercial vessels have the power demands and size to make a superconducting propulsion motor feasible, and of course propulsion that is of lighter weight and smaller size benefits vessels of all types, giving them the ability to carry more cargo and sail faster, but actual use is several years away. “Currently we are looking for partners for ventures in the commercial market," said Fredette.
Fredette explained that the “high" temperatures that characterize this technology are high only in a relative sense.
“We are talking about temperatures in the 50 to 80 kelvin range or about minus 300° Fahrenheit," he said. “Lower temperature superconductors (less than 50 kelvins) require the use of expensive cryogenic equipment and are mainly used today in medical MRI machines."
An HTS motor has many of the same components as a standard electric motor. For example the stator (electromagnet) serves the same function. It is the rotor (rotates inside the stator) that is totally different. It is wound using a hair-thin wire that has a nickel-tungsten substrate on which is coated a ceramic material called yttrium barium copper oxide, or YBCO. This wire is cooled by an external refrigeration system using gaseous helium.
“The superconductor wire can carry 150 times the power of similar sized copper wire. The motor provides the U.S. Navy with a truly transformational capability relative to size, stealth, endurance and survivability, providing our Navy with a clear performance advantage for years to come," said Dan McGahn, senior vice president and general manager of AMSC.
Typically a system using an HTS motor would have a gas turbine driving a generator that would power the motor.
AMSC and Northrop Grumman shared the work, with AMSC serving as the prime contractor for the research and development phase.
Running an HTS electric motor in reverse would create a generator and that is of great interest in wind turbine technology that is looking for smaller, more efficient generators to produce electricity.
By Professional Mariner Staff