November 4, 2002

Key superconductor component shipped
Becuase of their promise of major size, weight and space saving, superconducting electric motors could well be the next big breakthrough in marine propulsion. That breakthrough may now be a lot nearer. American Superconductor Corporation (AMSC) has completed the manufacture and testing of the rotor assembly for the world's first high temperature superconductor (HTS) ship propulsion motor. AMSC is manufacturing the prototype motor under a contract from the U.S. Navy's Office of Naval Research (ONR).

The rotor assembly has been shipped to the U.K., where ALSTOM's Power Conversion Business has been contracted by AMSC to build the stator and to take care of the final assembly, including factory testing of the complete motor, by July 2003. At that time the Navy will begin testing the motor.

The power rating of the high torque, low speed (230 rpm) HTS motor is 5 megawatts, or 6,500 shaft horsepower. The rotor assembly--the heart of the motor--includes the rotor shaft, torque tube, HTS coils -- wound with AMSC's HTS wire -- a power electronic exciter, and integrated refrigeration components used to cool the HTS coils.

AMSC's HTS rotor windings incorporate a new design that increases the efficiency and the compactness of the motor. The 5 MW/230 rpm HTS motor will be one-half the size and weight of a conventional motor built with copper coils, says AMSC. The electrical losses of this motor will be less than half those of a conventional ship propulsion motor because of the higher electrical efficiency provided by the HTS wires employed.

"The ship propulsion motor we are developing for the U.S. Navy represents a significant milestone in the commercialization of HTS rotating machines," said Dave Paratore, VP and GM of American Superconductor's Electric Motors and Generators business unit. "We believe HTS propulsion motors will revolutionize the commercial marine and naval ship industries because of their significantly smaller size and weight, and their higher electrical efficiency, which translates into significant fuel savings. Our goal is to begin deliveries of 5 MW ship propulsion motors to integrators of commercial ship propulsion systems in two to three years."

In addition to being a critical product development milestone, the low- speed, high-torque 5 MW motor is the power rating required today to propel many types of passenger and merchant vessels. The significant advantages of HTS motors in efficiency, weight and volume relative to conventional motors are expected to enable ship architects, builders and operators to capitalize on more cost-effective designs that allow more cargo or passengers to be transported, and in some applications, and at increased speeds with new hull designs. Better efficiency, less weight, and less space have been characterized as the "Holy Grail of ship designers" by Kvaerner Masa Marine, a noted naval architect and marine consultancy.

Paratore noted that the next key steps in the development of military and commercial HTS ship propulsion motors will be the demonstration of a 25 MW/120 rpm motor. "While our 5 MW motor is already a commercially viable size, we also intend it to be a risk mitigation step toward the development of HTS motors with power ratings up to about 40 MW, which we intend to have as part of our product portfolio along with HTS generators that will supply the electricity to run the motors," said Paratore. "With motor designs at these power ratings, we will be able to meet customer requirements across a broad spectrum of applications and sizes."

AMSC quotes projections that the global market for electric ship propulsion motors will grow from $400 million per year today to $2 billion to $4 billion per year in ten years, a compound annual growth rate of more than 20 percent. A recent study by MSCL Inc., an international maritime consultancy, stated that "Ship builders and naval architects ... all agree that electric drive is becoming the drive system of choice for many new ships of every type and it is expected to become dominant in the market within the next decade."

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