Boosting Your Bottom Line: PMAC Motors Optimize Systems

Permanent-magnet AC motor-control packages can achieve high energy savings when operated under variable loads and high duty cycles. These motors also eliminate rotor losses, enhance speed and torque regulation, and extend motor equipment life, compared with conventional induction motors. Photo: NovaTorque Inc., Fremont, CA, novatorque.com

By Walker Larsen, Program Manager Consortium for Energy Efficiency (CEE)

Proper selection and sizing of motors, controls, transmission, and application equipment, as well as good operations and maintenance practices, help you get the most out of your electric-motor-driven systems. Now, facility operators have opportunities to optimize system performance, thanks to the growing availability of high-efficiency motor technologies packaged with controls. This development could simplify matters for anyone who buys and operates electric motors that serve variable loads.

Motor Decisions Matter recently looked into permanent-magnet AC (PMAC) motors as an interesting example of a motor technology that is usually packaged with controls to optimize performance. With this technology, magnets are embedded directly into the rotor, establishing permanent magnetic fields. PMAC motor-control packages can achieve high energy savings when operated under variable loads and high duty cycles. When compared with traditional induction motors and implemented in proper applications, PMAC motors eliminate rotor losses, enhance speed and torque regulation, and extend motor equipment life. They also have higher power density and smaller frame sizes than induction motors of comparable horsepower, so you can use them where space is limited. This integration of motors and controls will not only help you achieve greater savings, but may also help reduce the complexity of decision making surrounding system components.

We see a similar effort to optimize electric-motor components for energy performance occurring at the federal level. The U.S. Department of Energy (DOE), Washington, recently proposed energy-conservation standards for a subset of commercial and industrial clean-water pumps between 1 and 200 hp. The proposed standards are based on a metric called pump energy index (PEI), which incorporates not just the efficiency of the pump itself, but also the energy use of the motor that drives the pump and any associated controls. The inclusion of motors and controls, and differentiating pumps operating under constant and variable loads, attempts to incorporate system features into minimum energy-performance standards, and may reflect a trend toward component integration to achieve the most efficient outcome.

As high-efficiency technologies converge to optimize performance, it’s likely that motor users will have greater opportunities to purchase and replace motors and drives with packaged components that are designed to complement each other. This is promising from an energy- and cost-savings potential. According to the DOE analysis, the proposed pump-system rule will save approximately the annual energy use of 2.8 million homes and as much as $1.1 billion over 30 years.

For more information specific to PMAC motors, you may view recent webinars that outline the basics of the technology on the MDM Events page at motorsmatter.org. The website also features a supplemental Q&A section that elaborates on the role of controls. MT

wlarsen@cee1.org

The Motor Decisions Matter campaign (MDM) is managed by the Consortium for Energy Efficiency  (CEE1.org), a North American nonprofit organization that promotes energy-saving products, equipment, and technologies. Contact: mdminfo@cee1.org or 617-589-3949.