23 Jul 2024


Nema index compares VSDs to maximise energy savings

The US-based National Electrical Manufacturers Association (Nema) has published a procedure that allows variable-speed drives to be compared to optimise their energy savings. The organisation has also produced a guide that defines a process for validating digital models for predicting the efficiency of electric motors.

Nema’s new MG 10011-2022 standard (Power Index Calculation Procedure – Standard Rating Methodology for Power Drive Systems and Complete Drive Modules) discusses a power index (PI) for power drive systems (PDSs), which can help to cut carbon emissions, enable smart manufacturing technologies, and improve energy savings. A PDS is defined as a motor coupled with a VSD (variable-speed drive).

“In my 30-plus years of promoting motor efficiency, there has never been an opportunity to save energy that comes close to the adoption of the PDS replacing mechanical control technologies,” says Rob Boteler, chairman of Nema’s Motor and Generator Section’s Energy Management Committee, and Nidec’s government relations representative in the US.

The PI value allows PDSs and drives to be compared for optimal energy savings. It can be applied to a variety of motor types and provides an easy-to-use metric, similar to car mpg ratings.

Nema worked with the Northwest Energy Efficiency Alliance (NEEA) to develop the Power Index rating, providing a streamlined method to evaluate the reduction in power and energy savings achievable by using a PDS to control motor speeds.

“This metric will be an important tool for utilities and regulators, who can utilise PI in their incentives programmes to encourage the selection of motors and controls that will result in significant energy savings,” explains NEEA codes and standards engineer Nicole Dunbar. NEEA is an alliance of more than 140 utilities and energy efficiency organisations.

“This standard represents an important change in how we think and talk about the potential energy savings from motors and drives,” adds Dale Basso, who chairs Nema’s Motors and Generators Section and is WEG’s motors manager in North America. “Power drive systems represent the next big opportunity for industry, utilities, and end-users to acquire energy savings from motor-driven systems.”

The standard is available from Nema’s Web site as a free electronic download or for $84 in a hard-copy version.

The second new publication from Nema – MG G2-2021: A Motor and Generator (IS-MG) Section Guide for Validating an Alternative Efficiency Determination Method (AEDM) – defines a process for validating a digital model for predicting the efficiency of electric motors. The process can be used in conjunction with laboratory data to combine the losses of multiple components in more complex systems.

“This guide provides a means to obtain accurate motor efficiency predictions while reducing the number of physical samples requiring testing,” explains Nema’s industry director for industrial systems, Fern Abrams. “It adds value to the industry because the use of validated AEDMs reduces the costs associated with testing and certifying to Department of Energy regulations and other national minimum energy performance standards.”

Nema MG G2-2021 is available from Nema’s Web site as a free download or for $56 in hard copy.

Nema represents almost 325 electrical equipment and medical imaging manufacturers who together employ 370,000 people in more than 6,100 facilities in the US. They produce $130bn in shipments and $38bn in exports every year.

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