September 28, 2004
Milestone for superconductor motor
American Superconductor Corporation (NASDAQ:AMSC)reports that its prototype 5-megawatt (MW) High Temperature Superconductor (HTS) ship propulsion motor has been demonstrated successfully at full load, under steady state operational conditions, at the Center for Advanced Power Systems (CAPS) at Florida State University in Tallahassee.
The motor was developed under contract with the U.S. Navy's Office of Naval Research (ONR) to prove the viability of HTS technology for both military and commercial marine propulsion.
After the 5-MW motor completes load and ship mission profile simulation tests at CAPS, it will undergo additional performance testing at the Naval Surface Warfare Center, Carderock Division in Philadelphia. The Navy will then define further land-based and at-sea testing for this motor.
"We continue to be pleased with these new test results on the 5-MW superconductor motor," said Rear Admiral Jay Cohen, Chief of Naval Research. "The HTS ship propulsion motors we have been developing continue to perform above our expectations and are providing an important new option for future Navy propulsion systems."
HTS motors are as little as one-third the weight and one-half the size of copper-based motors of the same power and torque rating, which means Navy ships can carry more fuel and munitions and have more room for crew's quarters and weapons systems. Commercial ships can carry more passengers and cargo.
In addition, HTS motors operate with higher fuel efficiency and will have lower maintenance costs than their conventional copper counterparts. These advantages promise to be provided at a cost equivalent to conventional motors of the same power and torque rating.
Load testing demonstrates how a motor performs under the stresses and operating conditions it undergoes when powering a vessel at sea. This final development stage of the motor provides engineers and ship propulsion integrators with vital information regarding design options and the operating characteristics of the new superconductor motors.
An important aspect of the new results obtained at CAPS on the 5-MW motor is the validation of AMSC's electromagnetic, mechanical and thermal analytical models for HTS ship propulsion motors--a vital step in the development cycle for advanced electrical machines.
AMSC says the HTS motors it is developing involve no major changes in fundamental motor technology. The machines operate in the same manner as conventional motors, gaining their substantial advantages by replacing copper rotor coils with HTS rotor coils. The rotors of HTS motors run "cold," so they avoid the thermal stresses experienced by conventional machines during normal operation. The inability to achieve proper thermal management has been a key impediment in developing power dense, high torque motors required for naval and commercial marine applications. Stresses caused by heat in other advanced, high power motors often necessitate costly motor repair and refurbishment.
AMSC's 5-MW (6,667 shaft horsepower) HTS propulsion motor rotates at 230 revolutions per minute (rpm) and generates 200,000 Newton-meters of torque at full power. This power and speed rating are typical for copper-based electric propulsion motors currently used in ferries and small cargo ships around the world. This class of superconductor motor also is expected to become a standard power rating for certain military ships.
The 5-MW HTS motor is a subscale version of the 36.5-MW (49,000 horsepower), 120 rpm HTS motor currently being built by AMSC and Northrop Grumman under a $70M three-year contract from ONR. The 36.5-MW motor, which will produce 2.9 million Newton-meters of torque, is due to go through a Detailed Design Review with the Navy in October--the next major step in its development.
On schedule to be delivered in the spring of 2006, the 36.5-MW motor is being specifically designed to provide propulsion power for the next generation of Navy warships.
A motor of this scale also has direct commercial application in large cruise ships and merchant vessels. As an example, two 44-MW conventional motors are used to propel the Queen Elizabeth 2. These motors each weigh over 400 metric tons; the 36.5-MW HTS motor will weigh approximately 75 metric tons. Newer vessels, such as Queen Mary 2, which has a total propulsion requirement of 84-MW, are seen as ideal candidates for HTS motors.