sealPurdue News

August 1999

New electrical transformers will improve power quality

WEST LAFAYETTE, Ind. -- An engineering consortium led by Purdue University and the University of Missouri has taken a major step toward replacing the century-old technology behind the numerous, oil-filled power transformers that hang like icons from utility poles in residential neighborhoods.

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The consortium developed a new class of transformers that will smooth out the uneven voltages that plague today's grid and prematurely age electrical hardware ranging from light bulbs to motors to power supplies in electronic equipment. They are designed with so-called "solid state" technology, meaning they rely primarily on semiconductor components such as transistors and integrated circuits instead of the heavy copper coils and iron cores of conventional transformers.

The work is sponsored by Asea Brown Boveri, an engineering and technology company with headquarters in Zurich, Switzerland. A patent recently was issued for the solid-state transformer, which over the next decade is expected to begin replacing existing technology, says Scott Sudhoff, an associate professor in the Purdue School of Electrical and Computer Engineering.

Transformers are essential elements of the power grid; they convert the high-voltage electricity delivered by power lines to the 120-volt supply needed for consumers. Typically, one transformer supplies power to several homes. They come in three varieties: the pole-mounted canisters; ground-level metal boxes commonly painted green or blue; and, rarely, underground transformers.

Although the solid-state transformers may not look very different on the outside, they promise major advantages, most importantly in an area referred to as power quality, which is profoundly influenced by users of the grid. For example, some power equipment in homes, businesses and industry introduces electrical "pollution" that is passed on to neighbors, causing motors in various appliances to run less efficiently, heat up and go slower. The pollution causes voltages to fluctuate, affecting electrical devices such as light bulbs, which flicker and burn out faster. Heavy loads in one user's appliances can reduce the voltage for neighboring users and cause power outages.

"Your neighbor directly impacts your power quality," Sudhoff says.

Solid-state transformers would eliminate all such power-quality problems. They also would reduce the amount of current actually required to supply devices such as electric machinery, cutting down on losses associated with the transmission of electricity throughout the power grid. In addition, solid-state transformers represent an environmental improvement because they do not contain mineral oil, an insulation that can leak and pollute the environment.

Another drawback of conventional transformers is that they continually waste electricity.

"Even if you are away from home and nothing in your house is on, there are still losses in the transformer that go on all the time, and the utility pays for those losses," Sudhoff says, noting that the solid-state variety could reduce such waste.

And, while costs for materials used in conventional transformers are static, the costs associated with their solid-state counterparts are rapidly going down.

The transformers are being developed by the Energy Systems Analysis Consortium (ESAC), made up of Purdue, the University of Missouri-Rolla, the University of Wisconsin-Milwaukee, the U.S. Navy Postgraduate School and the U.S. Naval Academy. Asea Brown Boveri Ltd. owns all rights to the transformer patent.

A paper about the work was presented recently during a utility conference sponsored by the company. The paper was written by Sudhoff, Edward R. Ronan Jr., an engineer at the University of Missouri, Purdue engineer Steven F. Glover, and Dudley L. Galloway, a design engineer at the company's distribution transformer division.

Source: Scott Sudhoff, (765) 494-3246;

Writer: Emil Venere, (765) 494-4709;

Purdue News Service: (765) 494-2096;

NOTE TO JOURNALISTS: Copies of the paper mentioned in this news release are available from Emil Venere at the Purdue News Service, (765) 494-4709,


Scott Sudhoff, left, and research engineer Steve Glover work on a solid-state transformer. High voltage, roughly 7.2 kilovolts, comes in at the bottom of the picture and is converted to the 120-volt household current needed to run the light bulbs at the opposite end of the table. (Purdue News Service photo by David Umberger)

Color photo, electronic transmission, and Web and ftp download available. Photo ID: Sudhoff.transformers

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