American Superconductor Corporation and Rockwell Automation have announced the successful operation of the world's first 1,000 horsepower (hp) high temperature superconducting (HTS) motor. This new motor was designed to utilize HTS wires instead of copper wires on the rotating shaft of the motor. American Supercon-ductor studies indicate the key benefits of using HTS wires are significant reductions in the size and manufacturing cost of industrial and ship propulsion motors, as well as increases in electrical efficiency.
"The successful demonstration of the 1,000-hp HTS motor is a significant engineering achievement," according to Joseph D. Swann, president, power systems, Rockwell Automation. "Through our participation in this project, Rockwell Automation hopes to further the development of this important energy-saving technology, paving the way for ground-breaking research and development that will contribute to the commercial success of superconductivity."
Industry experts estimate that the current international market for industrial motors with power ratings of at least 1,000 horsepower is approximately $1 billion per year worldwide. The market for electric generators over 30 megawatts, which involve the same fundamental technology as motors, is approximately $2 billion per year.
Large horesepower motors are the workhorses of industry. Today, conventional motors utilize approximately 25 percent of all electric power generated in industrialized countries. The U.S. Department of Energy estimates that higher efficiency HTS motors could save U.S. industry billions of dollars per year in electrical operating costs. These gains in operating efficiency also mean more electricity available for the new digital applications of electricity.
"Our HTS wires not only operate with higher electrical efficiency, they are able to carry more than 100 times the power of copper wires with the same dimensions," said Greg Yurek, chief executive of American Superconductor.
"The higher power density of HTS wires is the basis for disrupting the global industrial motor business -- making it increasingly profitable through reductions in motor manufacturing costs by 25 to 40 per cent. These reductions are achieved through the implementation of innovative designs and reductions by up to a factor of three in the size of industrial motors -- all made possible by HTS technology." The 1,000-hp motor follows demonstrations over the last decade of a series of HTS motors with ever increasing power ratings. Success of the 1,000-hp motor depended on the development of higher performance HTS wire and the creation of new designs for components of the motor.
The 1,000-hp HTS motor was developed under the auspices of the U.S. Department of Energy's (DOE) Superconductivity Partnership Initiative. The intention of the DOE program is the promotion of advanced high efficiency motors based on superconducting technologies.
"Superconducting power technologies can help address concerns about the reliability of the electric grid," said U.S. Energy Secretary Bill Richardson. "DOE's support for these types of projects promotes our mission of efficient, environmentally-friendly energy solutions."
American Superconductor has more recently focused on the design and development of HTS motors that fully leverage the higher power density of HTS wires. The company has already tested key components for its new, patented design for ultra-compact HTS motors. It believes these motors will be much less expensive to manufacture compared with conventional motors that use only copper wires and will be more energy efficient as well. American Superconductor expects to have its first 5,000-hp HTS ultra-compact motor ready for testing in the Spring of 2001. It has already let contracts for manufacture of certain components of this motor, which it sees as the market entry point for HTS motors. The company is also working under a U.S. Navy contract on design concepts for 33,000-hp ship propulsion HTS motors.
Technical Background
Superconductors are materials that carry large quantities of electricity with zero electrical resistance when cooled to very low, or cryogenic temperatures. While superconductors have been known for decades, the only commercial application until recently was in medical magnetic resonance imaging (MRI) devices. These devices utilize low temperature superconductor (LTS) wires.
In 1986, two IBM scientists discovered a new family of superconductor materials that still require cooling to cryogenic temperatures, but that operate at 5 to 20 times higher temperatures than the old LTS materials. The new materials, which are ceramic compounds, have become known as high temperature superconductors (HTS). The lower cost of cooling these new materials significantly enhanced the commercial economics of superconductor applications, and created the possibility of using high power density superconducting wires in electric power applications, such as power cables, motors and generators.
How do superconducting motors differ from conventional motors?
Superconducting motors are a new type of AC synchronous motor that employ HTS (high temperature superconductor) windings in place of conventional copper coils. Because HTS wire can carry significantly larger currents than can copper wire, these windings are capable of generating much more powerful magnetic fields in a given volume of space. Advances in coil design make it possible for a superconducting machine to match the power output of an equally rated conventional motor with as little as one-fifth the size and weight. The smaller size and compact nature of superconducting motors allows them to be manufactured at lower cost than equivalent conventional motors.
Additionally, the replacement of conventional copper rotor windings with non-resistant HTS coils results in sharply reduced electrical losses in the rotor and armature. Conventional motors are made primarily of iron, which makes them heavy and increases the frictional load seen by the motor bearings. All iron can be eliminated when constructing superconducting electrical machines with HTS windings. The removal of the iron teeth in the armature not only makes superconducting motors lighter (with lower inertia), it also leaves more room for armature copper, which lowers the electrical losses and also improves machine efficiency. These reductions in losses result in lower operating costs than conventional motors.