Motion Control Resources
- This technical feature is filed under:
What You Need to Know About the New Motor Efficiency Standards
by Kristin Lewotsky, Contributing Editor
Motion Control & Motor Association Posted 06/29/2015
Based on a 2006 study by the US Department of Energy (DOE), roughly 1430 million kWh of energy was used by motor-driven equipment in the United States . In the industrial space, in particular, electric motors accounted for about 17% of total US usage and 62.5% of total US industrial usage. Granted, most of this represented electrical energy converted to work, but some represented losses. Small wonder that as concerns rise around issues like climate change and energy independence, countries around the globe have begun regulating motor efficiency. We define motor efficiency for constant operation, which means that it applies to fixed-speed operation but not to stop-start motion. Continuous-duty-cycle motors that run compressors, fans, and pumps, for example, may fall under the regulations but the servo motors operating that hundred-axis printing line will not.
Don’t get smug, though. There are a number of reasons that Motion Control & Motor Association (MCMA) members and the broader readership of this site need to pay attention to the ongoing process of efficiency regulations: factory floors feature plenty of fixed speed motors, including the ones that run the fans that cool control cabinets; permanent-magnet motors might be an easier replacement motor compared to efficiency compliant induction motors; and permanent-magnet motors might also help machine builders deliver the next level of efficiency in continuous-duty-cycle motors.
The evolution of efficiency
First, a bit of history. In the United States, the Energy Policy Act of 1992 launched the process of regulating motor efficiency with the (sometimes referred to as the integral horsepower rule) . This ruling mandated general-purpose 1-to-200 hp polyphase AC induction motors meet energy efficient performance as defined by the National Electrical Manufacturers Association (NEMA) standard MG 1, table 12-11. In 2007, the Energy Independence and Security Act (EISA) upgraded this regulation, calling for general-purpose 1-to-200 hp motors to now meet the more stringent NEMA Premium Efficiency levels as defined by MG 1, table 12-12. It also broadened the mandate by applying the Energy Efficient requirements to both additional types of 1-to-200 hp motors and to 201-to-500 hp general-purpose motors.
Elsewhere around the globe, similar activities have taken place, with the European Union, Canada, Australia/New Zealand, China, and Brazil all developing their own sets of standards (see figure 1).
In 2010, the effective date of the EISA regulation, NEMA and a group of energy-focused organizations aligned to create the Motor Coalition, working together to create a strategy that would deliver the greatest benefit in terms of energy savings while minimizing the impact on industry and simplifying enforcement.
This group contributed to the development of the next major update to the Electric Motor Rule. One approach would have been to develop a new, higher level of efficiency for induction motors might have compromised product utility and forced expensive, wholesale design changes that delivered only small savings. Instead, the group helped develop a ruling that focused on aggregate savings by closing loopholes and extending coverage to bring a large number of formerly exempt motors under regulation . Effective June 1, 2016 and designed to revise the Code of Federal Regulations 10 CFR Part 431, the new expanded-scope rule requires nearly all single-speed induction motors from 1 to 500 hp, including enclosed 56 frame motors 1 HP and larger, to perform at Premium Efficiency level; in addition, a small number of previously unregulated motor types will now be held to the Energy Efficient standard . This combined with the expanded scope rule promises to reduce carbon emissions by 395 million metric tons and save more than $41.4 billion in energy costs for products shipped from 2016 to 2045.
Those weren’t the only changes. In January 2013, the DOE published the Small Electric Motor Rule that covered select small-form-factor (NEMA 48, 52 and 56) motors. In June 2014, the DOE clarified the rule to apply to open, drip-proof motors, with the changes effective March 2015. The update applies to single-phase and polyphase motors rated from ¼ hp to 3 hp, and is sometimes referred to as the fractional horsepower rule – which is incorrect, for obvious reasons. The initial version of the regulation applies to continuous-duty motors. A host of definite and special purpose motors enjoy an exemption from the rule, including totally enclosed non-ventilated (TENV) , totally enclosed, fan-cooled (TEFC), submersible, liquid cooled, encapsulated, nonstandard mountings, etc.; however, polyphase 1HP and above will be covered by the integral rule in June 2016.
At a glance, the Small Electric Motor Rule appears to exclude more components than not, and contain more than a few ambiguities . Then again, so did the initial versions of the Electric Motor Rule. With every successive iteration, however, performance levels increased and the coverage area broadened. Look for the same evolutionary process in the case of fractional horsepower motors.
It’s important to note that these regulations place the responsibility for compliance on the manufacturer, not the customer. Purchasers simply need to specify the motor with the performance application but they also need to take care that their vendors are aware of the location to ensure that they deliver a compliant product.
Techniques for increasing efficiency include using lower-loss electrical steel, the use of additional laminations or cast steel rotors, and additional copper windings. Those changes increase costs. They also can produce motors with longer or larger diameter frames. This can be a particular problem for small motors, which typically get applied in space-constrained applications that may not fit larger housings.
“That’s the concern that we have tried to voice to the DOE from the beginning, that small motors are placed in tight spaces and we don’t have magic,” says Dale Basso, motors manager, WEG Electric Corp. (Jaraguá do Sul, Brazil). “If the customer has squeezed it in and we have to make the motor bigger to make it more efficient, the user in the field buying a replacement is going to suffer. OEMs are going to have to redesign equipment to make everything fit but their end customer is the guy who is really going to hurt because they have a $2,000 piece of equipment and they want a new $200 motor. Instead of just being able to replace it, they now have to buy a new piece of equipment.”
The OEM or end user then faces a series of choices. They can stockpile their existing motors prior to the effective date of the ruling, assuming they take action in time. This is only a stopgap, however, not a real solution. Alternatively, they can physically change the system. For an OEM building a new machine, or even one revising an existing design platform, this can range from merely inconvenient to difficult and expensive. In the case of deployed equipment, though, making modifications can range from challenging to impossible.
Instead of changing the machine, they might look for a specialty motor, but given that most motor manufacturers focus on products they can make in volume, getting a handful of these motors to use as replacements can be both difficult and expensive. Permanent magnet motors provide an alternative. On the up side, they do offer the efficiency, but they also increase cost. Still, weighed against the alternatives, they may be a choice worth considering.
The next generation
Crafting standards and regulations is a thankless business; no sooner has the latest version been released than work begins on the next iteration. In the case of the Small Motor Rule, the next revision will cover enclosed motors and extend to lower powers. Not just major manufacturers but OEMs and end-users need to get involved to ensure that the result is both useful and realistic. “We can’t just leave it up to the DOE to invent things on the fly because when that happens, we end up with rules that are very difficult for us, and the end users,” says Rob Boteler, manager of government relations at Nidec Motor Corp. (St. Louis, Missouri) and chairman of the energy management committee for the NEMA Motor and Generator Section.
On the bright side, it’s an iterative process, notes John Malinowski, senior manager for industry affairs at Baldor Electric Co. (Wallingford, Connecticut) and past chairman of the NEMA Motor and Generator Section. Initial drafts would focus on induction motors but as test methods and product definitions become more defined, future passes can focus on advanced technologies like switched reluctance, permanent magnet, synchronous reluctance and electronically commutated motors. “It’s likely that the motors covered are going to be continuous-duty motors only and probably not include incremental motion servo motors,” he says. “But a lot of those companies make permanent magnet motors that are used for continuous type applications with servo technology, so those companies may be interested in participating in the standards to develop.”
Meanwhile, the efficiency march continues for integral horsepower motors. WEG, for example, is already at work on motors to meet the anticipated efficiency levels IE5 rating, which is above NEMA’s forthcoming Super Premium standard (see figure 2). Interestingly, one of the approaches for delivering the required performance appears to be working with permanent-magnet technology, for example in applications like pumps and fans running at variable speeds with light partial loads.
In a standard induction motor, the rotor represents roughly 25% of losses. Using a permanent magnet design can eliminate most of that loss. Meanwhile, the approach also provides another way to increase efficiencies. Standard induction motors deliver peak efficiency while operating at full speed and load. When the load drops, efficiency decreases significantly. For a motor running at three quarter speed in fan application, for example, the motor runs at one half load, which reduces efficiency by several percent. In the case of a permanent magnet motor, the efficiency remains quite consistent. Lower losses means less heat to dissipate. Previously, heat generated in the rotor had to be radiated across an air gap and then dissipated by the winding and the frame – the greater the amount of heat, the bigger the motor. Less heat to dissipate means it’s possible to shrink the frame size. “It’s important that OEMs and end-users can replace the old motor with a new motor the same size,” says Basso. “Using permanent magnets takes it to a new level where now you can actually decrease the size of the motor and move up to an IE4 level.”
Permanent magnets, particularly rare-earth magnets carry higher cost, of course. That can be offset by the lower weight, however. Basso sees using this approach to move to IE5 levels and beginning to apply variable-frequency drives to many of these formerly fixed-speed applications.
That said, motors in general are already highly efficient and are approaching the practical limit. The next part of the strategy will involve a systems-level approach for essential applications like fans, pumps and compressors. In these cases, the components that squander the most energy are not the motors but the other elements such as bearings and gears. The effort is already underway to craft a new set of standards that could be in place as early as 2019 or 2020. “That could change a lot of the componentry that OEMs might buy to install in their machines, and it’s going to change the systems that the end users buy that would be retrofit for what they’ve already got installed,” says Boteler. “Everybody needs to be mindful of what’s kind of hanging out here over their heads. Things are going to change.”
Thanks go to Eric Eekhoff, electrical design engineer and Ed Tullar, sales manager at Groschopp Inc. (Sioux Center, Iowa) for useful background conversations.
- Premium Efficiency Motor Selection And Application Guide, US Department of Energy, DOE/GO-102014-4107, February 2014. A detailed, quantitative overview of the category.
- Electric Motors standards portal, US Department of Energy. Discover a treasure trove of information about the regulation, including the actual document itself.
- The Impact of the Integral Horsepower Amended Rule, NEMA, April 2014. A summary of what the rule means for users, which motors qualify and which do not.
- Small Electric Motor standards portal, US Department of Energy. This page provides access to the standard, recent updates, test procedures, and ways to apply for waivers.