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Copper-based casting improves motor technology
By Shelia Watson
Contributing Writer
A copper-based casting technology program, headed by ATI, an affiliate company of the South Carolina Research Authority, and jointly sponsored by the Defensive Logistics Agency and the Army Research Labs in Aberdeen, Md., has shown increased efficiency ratings in electric motors that could have far-reaching effects across several industries.
According to the program’s manager, Chuck Stark, the objective is to develop, demonstrate and deploy applications of die-cast copper and copper-based alloys to make lighter, more efficient motors and component parts.
The program, which has a contract value of $4.39 million over a four-year period, from July 2004 to July 2008, involves designing/redesigning, building and testing copper rotor motors to improve electrical energy efficiency.
Stark explained that copper is a better conductor of electricity and would be preferred over aluminum as the material to put in motors. However, the die-casting process requires much higher heat for copper—1,100 degrees compared with 350 degrees for aluminum—and the tools used to cast copper would not last as long.
“The life of the mechanical die that these got poured into was the driving factor for which material was used,” Stark said. “The manufacturing cost over time would be higher for copper because of the tools having to be replaced so often.”
However, research from the program has resulted in a modified die for use with copper. And the overall effects of using copper are dramatic, Stark said.
“Here’s what happens,” he said. “Motors today have about 90 percent efficiency rating. We’re looking at closing the gap to about 92 to 94 percent efficiency, which is a significant jump.”
Significant is right. The U.S. Department of Energy reports that medium-power induction motors (1 to 125 horsepower) use about 60% of electricity supplied to the U.S. industry—or 23% of the total consumption in the United States. A 1% increase in motor electrical energy efficiency could save up to 9 billion kilowatts per year—or $630 million in electricity (at 7 cents per kW-hr, which underestimates average consumer rates).
Some of the advantages copper has over aluminum include improved efficiency and a lower operating temperature, which will allow the motor to run cooler.
“For every 10 degrees you can lower the temperature, you can increase the life of the product by 50 percent,” Stark noted.
Besides energy savings and cost savings, there would be potential space savings as well: Because of efficiencies in the manufacturing, the motor can be made smaller and lighter.
Smaller and lighter, Stark said, is preferred for autos, in aerospace applications to increase fuel efficiency and on board a ship, as electric power and space are a premium at sea.
“It’s an attractive piece of engineering for businesses across the spectrum,” he said. “It’s certainly attractive to the manufacturing sector. For the consumer, it’s good to have a more efficient machine that may have a longer life.”
Stark said there will likely be more useful applications for businesses than for consumers.
“Most small engines are used in business,” he said. “A 10-horsepower motor is a big animal. You probably wouldn’t have them in your home, but there are probably lots of them at Detyens Shipyard.”
Areas currently being considered for the copper-based casting products include military applications, particularly with shipboard and aerospace areas; agriculture machinery and tools; and hybrid electric vehicles.
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