Sidebar: Setting a Premium Standard

sidebar: setting a premium standard

In June, the national electrical manufacturers association, or NEMA, launched its Premium efficient electric motor program, to promote and encourage the installation of higher-efficiency motors. "The program was conceived and launched by electric motor manufacturers, including Emerson Electric in St. Louis; Rockwell Automation/Reliance Electric in Greenville, S.C.; GE Motors in Fort Wayne, Ind., and Toshiba International in Houston, among others," said Kyle Pitsor, industry director at NEMA.

Pitsor explained that the new program represents a needed consensus on premium efficiency motors, because each motor manufacturer had its own definition of premium efficiency. So did different utilities that offer rebates to manufacturers, processors, and building owners to install high-efficiency motors. "We based the program specifications—which will be added to the NEMA MG-1 standard—on the type of motor and its output. For example, a 10-hp, six-pole ODP motor would have to convert 91.7 percent or more of its electrical input into mechanical power," said Pitsor.

In general, Premium motors are 1 to 4 percent more efficient than today's "energy-efficient" electric motors. The NEMA Premium designation certifies that the motor meets or exceeds the association's specification, said Pitsor.

According to DOE estimates cited by NEMA, the program has the potential of saving more than 5,800 gigawatt-hours of electricity, while preventing the generation of 80 million metric tons of carbon into the atmosphere, over the next 10 years. This is approximately the equivalent of keeping 16 million cars off the road.

As chairman of NEMA's Energy Management Task Force, Robert Boteler, director of marketing technology products and services at Emerson Electric, was intimately involved with developing the NEMA Premium standard now available on his company's 1- to 500-hp motors. The actual design of Emerson's premium motors predates the logo launch last June.

"We used our own finite element analysis program to redesign our standard motors to deliver premium energy efficiency. Basically, this included adding special laminations to the rotor and stator, and adding more copper in the wire windings, and more aluminum in the rotor, which made the motors longer and larger," explained Boteler.

As a result of the design changes, Emerson's premium motors run cooler, enabling engineers to reduce the size of their cooling fans. This reduced the windage losses that cut motor efficiency. "Also, we reworked our motor bearings and the machining of our rotor surfaces, to increase efficiency," said Boteler.

About 90 percent of Emerson's premium, three-phase, industrial motors produce 50 hp or less for the company's traditional markets—namely, oil refineries, chemical processors, and pulp and paper plants. About 60 percent of those motors are used to power pumps; the remainder power fans and compressors.

While it is too early for Emerson and other manufacturers to have case studies of their NEMA Premium motors, Boteler recently analyzed the energy usage and needs of a local water utility whose pumps were powered by standard electric motors ranging from 40 to 400 hp.

"These motors are about 30 years old, having been rewound several times," said Boteler. "We estimate the cost of replacing them with NEMA Premium motors to be $48,000. The new motors would save $26,900 per year, giving a payback of about one and three-quarter years."