Energy efficiency by the numbers

Legislative and rare-earth-metal pressures add up to long-term savings for motor users.

By J. Stanton McGroarty, CMfgE, CMRP, senior technical editor

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Newer motor and drive technologies

Manufacturers have released technologies that are above premium efficiency, explains Malinowski. “These are not conventional AC squirrel cage induction motors, but motors with permanent magnet rotors, switched reluctance, synchronous reluctance, and other technologies, most requiring a drive for operation,” he says. “Drives are becoming more powerful and sophisticated at a more competitive price. New motor technologies are available that could be more power-dense — more horsepower in a smaller package — or much more efficient. Sophisticated users are adopting sustainable corporate policies based on using efficient technologies, not on lowest first cost.”

J. Stanton McGroarty, CMfgE, CMRP, is senior technical editor of Plant Services. He was formerly consulting manager for Strategic Asset Management International (SAMI), where he focused on project management and training for manufacturing, maintenance and reliability engineering. He has more than 30 years of manufacturing and maintenance experience in the automotive, defense, consumer products and process manufacturing industries. He holds a bachelor of science degree in mechanical engineering from the Detroit Institute of Technology and a master’s degree in management from Central Michigan University. He can be reached at or check out his .

One trend is to adopt a systems approach, rather than individual component replacement, adds Malinowski. “A matched system can be more efficient when sized for the particular application parameters,” he explains. “The system would include all components inside the electric motor: power distribution transformer, smart starter/soft starter/drive, motor, mechanical power transmission components, highest efficiency in driven load, and process control to make it work in harmony with other activities in the plant.”

For some applications, the economic potential of drives is more exciting than that of motor developments, says Douglas Weber, business development manager, Rockwell Automation ( “When you look at variable-speed motors and drives, in most applications the overall process efficiency that is gained by the application of a drive is so large that a gain in efficiency from 95% to 96% in the motor or drive itself is not really that significant,” he explains. “For drives, we've seen a continuous march of slowly increasing efficiency with each new generation. Those efficiency improvements are really driven by the desire to reduce the size, weight, and cost of drives, not directly by increasing efficiency. To reduce size, weight, and cost of a drive, you have to reduce the heat generated inside the drive, along with increasing your ability to remove heat from the drive. Reducing the heat means efficiency is also higher, but that is due to the focus on size, weight, and cost. There also may be a bigger effect going forward coming from the alternative energy space, especially the solar PV market, where the focus on efficiency is understandably much higher.”

Figure 3. Potential might exist for the expansion of variable-frequency drives into additional applications, where they aren’t yet applied.
Figure 3. Potential might exist for the expansion of variable-frequency drives into additional applications, where they aren’t yet applied. (Source: Rockwell Automation)

When you introduce variable speed to an application, you get such a huge benefit that an extra point of efficiency in the motor isn’t all that important, argues Weber. “It's been more of a focus for fixed speed motors,” he says. “However, we’ve seen an increase in interest over the last several years in efficiency, especially in the application of permanent-magnet motors to a broader range of applications. There also is a focus on innovation in new motor technologies by the motor manufacturers to gain additional efficiency. Another new area of focus would be fan efficiency.”

Weber sees potential for the expansion of variable-frequency drives into additional applications, especially retrofits, where they aren’t yet applied (Figure 3). “The biggest opportunity is in using more drives,” he offers. “Beyond that, equipment builders are increasingly looking to use machine efficiency as a marketing point for the equipment they sell. This is much more common today than it was even five years ago, and it’s driving the adoption of energy-efficient motor technology and drives into equipment.”

Integrated drive systems, including drives, motors, gearboxes and couplings from a single source supplier will be a trend for process control and energy savings, explains John Caroff, marketing manager, low voltage motors, at Siemens Industry ( “Offerings like this help end users reduce project development, engineering and commissioning timeframes by having a single point of contact for an entire drive system,” he says.

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