EEMODS '11—efficient motor systems conference: standards, new technologies
Energy Efficiency in Motor Driven Systems (EEMODS)—a notable international conference on electric motors, drives, and numerous related systems—drew some 150 attendees from industry, academia, government, research labs, and other service organizations to Alexandria, VA (greater Washington, D.C. area) during Sept. 12-14, 2011, to discuss, debate, and promote advances in energy-efficient technologies. This part 2 of two articles covers developments in efficiency standards and newer motor technologies.
Frank J. Bartos, P.E.
Held for the first time in the Americas, EEMODS `11 consisted of parallel presentation tracks, panel discussions, and several table-top exhibits. As explained in part 1 of the conference coverage (Ref. 1), “systems” aspects of efficient motor-driven equipment is drawing deservedly increased attention from developers and providers of the underlying technologies. Meanwhile, work continues to further advance the efficiency of motors.
MEPS around the world
Motor minimum efficiency performance standards (MEPS) formed the topic of one of EEMODS’ panel discussions. Andrew Delaski, ex-director of ASAP (appliance standard awareness project)—a broad-based coalition of agencies to promote energy efficiency of various appliances—stated, “Savings from standards grow over time from accumulated results and from [an influx of] new equipment.”
Because the U.S. Department of Energy is required to periodically amend existing standards, a likely upcoming change will be expanded definition of motors covered, followed by fewer exceptions to the definition. “Much better results are expected from an increased scope of motors covered than trying to further increase efficiency of existing motor classes,” Delaski added.
Sarah Hatch, senior project officer, Australian Government Dept. of Climate Change and Energy Efficiency, spoke about the MEPS environment and experience in Australia—a country with strong advocacy for efficient equipment regulation, where MEPS are mandatory and manufacturers and suppliers must register their products. “Ongoing education and compliance are likewise part of Australia’s E3 (equipment, energy, efficiency) program,” Hatch stated.
Among comments of Paolo Bertoldi, European Commission Directorate, JRC, Institute for Energy, were upcoming regulations from the European Commission that will require reporting of product efficiencies at 50% and 75% load, in addition to full load. “Overall, the objective of MEPS is to phase out the least efficient products,” Bertoldi said.
Dr.-Ing. Peter Zwanziger, of Siemens AG and CEMEP (European Committee of Manufacturers of Electrical Machines & Power Electronics), spoke about first experiences of CEMEP with new IE-class low-voltage ac motors as defined in International Standard IEC 60034-30. (See more at Ref. 2 about effective dates of European Union regulations based on IE classes for motors. IE refers to international efficiency.) Market penetration of IE2 motors (1st phase of regulation) has been held down by applications that fall outside of the ruling, among other factors. Zwanziger called the European market transformation “on track but in need of strong market sweeteners” and noted that some customers are interested in even higher (IE4) class motors for their new systems.
Looking ahead, Zwanziger noted that future legislation must not block the influx of permanent magnet (PM) motors, often cited as a prime IE4 candidate, while induction motors remain protected as “an economical but effective technology.” See more below, about alternative efficient motors.
How MEPS will likely impact system design was discussed by Phillipe Juhel of CAPIEL, (European low voltage switchgear and controller manufacturers association) France, in “Does the new EU regulation for energy-efficient motors change the way to design a system?” First phase of the recent EU regulations has gone into effect in mid-June 2011 (see Ref. 2).
Among CAPIEL’s findings were that reasonably short payback periods apply for IE2 and IE3 motors when running for 800 hours or more per year, as measured in reduction of life-cycle cost (LCC). Moreover, IE3 motors should be considered for use first in high-duty applications, where they can reduce environmental impact and may also reduce LCC.
“It’s not always obvious to use variable-speed drives (VSDs) with efficient motors,” Juhel said. “It depends on the application and system involved.” He gave an example of an airport horizontal belt-conveyor application using a 2.2 kW, 4-pole gear motor. The motor driven direct on line consumed less energy than when under VSD control, for operations up to 300 start/stop cycles per hour. “It was a case of lower power consumption at constant speed but higher consumption during startups,” Juhel noted.
Moving beyond MEPS
The presentation, “When enough MEPS is enough: Conflict of resource utilization between system efficiency gains and MEPS,” by Neil Elliott of ACEEE (American Council for an Energy-Efficient Economy) was part of another panel discussion. While continued efficiency standards activities remain useful, Elliott suggested moving beyond MEPS to system approaches. Motors, pumps, lights, some appliances, etc. have already been covered. “We’re beginning to hit the point of diminishing returns with components as MEPS become more and more incremental,” he said.
Use of the private sector’s limited resources might gain more results from developing newer technologies. Elliott contrasted a static approach of “perfection” (for example, developing the perfect induction motor) versus a continuous and changing approach of “excellence” that involves systems and energy management—where the big savings exist.
Other areas of potentially large energy savings were pointed out by Bruce Benkhart, director of Applied Proactive Technologies, in his presentation “Whole System Approach to Improving Efficiency in Industrial Facilities.” Benkhart listed candidates for energy savings such as direct-drive PM motors, change of gearing type, more VSDs applied to motor control, synthetic lubrication, etc. Use of helical gearing rather than worm gearing, for example, can be up to 20% more efficient. Bringing the majority of motor systems (more than 2/3) with centrifugal or variable-speed loads under VSD control could result in 5-50% energy savings. About 60% of the total motor population fits that type of loading, according to Benkhart.
Motor rewind issue
Overall, motor population efficiency is expected to increase through attrition of older units. However, attrition may take decades due to long product life and motor rewind policies, among other factors, Benkhart explained.
Rewinding of old motors is often a fact of life for machines rated 50 hp (37 kW) or larger. This rule-of-thumb in industry happens because of substantial first cost of the motor and inherently higher original efficiency of larger units.
This hindrance to greater market penetration by new, energy-efficient motors was noted by other EEMODS presenters. Some limitation on rewinding after a certain age of the motor may be a future development. One of the presenters, Conrad U. Brunner—director of A+B International, Switzerland, and operating agent for 4E EMSA, (Electric Motor System Annex)—proposed eliminating motor rewinds after 20 years of service life to accelerate influx of more efficient motors.
Alternative efficient motors
The venerable induction motor continues to serve as the workhorse of electric motors, but other technologies are coming on stage. “Advanced/alternative motor (AAM) technologies market implementation,” presented by Rob Boteler, consultant for Nidec Motor Corp., provided insight on the approach OEMs take to adopt AAM technologies for their motor-driven systems. “Accelerating the adoption rate of new technology is proving difficult and must include service, supply, and other considerations,” Boteler said. AAM technologies also involve risk assessment and a need to assure customers that claims of energy savings are deliverable.
“Energy savings for cost reduction rate only third-place motivation when OEMs consider new technology purchases,” Boteler noted. Initial cost and improved system performance came in ahead of energy savings considerations.
Careful evaluation and total understanding of the process application is needed to make the best motor technology decision. This can range from speed, torque, duty cycle, and controls to environmental specs, interfacing, life expectancy, agency approvals, and more. Another possible item to consider: Could a low-efficiency gearbox be eliminated from the system, for example.
Alternative efficient motor technologies include permanent magnet (PM) synchronous motors, which offer the best specific torque per volume; switched reluctance (SR) motors may provide a future impact, Boteler explained.
SR motor technology also received attention in “Electric motors for the modern world—a look at new motor technologies,” presented by Satish Rajagopalan of EPRI (Electric Power Research Institute). Renewed interest in SR motors comes from absence of permanent magnets in the design, which makes them an alternative to motors requiring costly (and scarce) rare-earth magnets. Notable usage has been in the medium-power market (<300 kW), such as household appliances and automotive applications, according to Rajagopalan. However, SR motors have some noise, torque ripple, and vibration issues that need to be minimized for wider application success.
Another IE4-class candidate was the synchronous reluctance motor, which starts like an induction motor, then locks into synchronism at operating speed. “Absence of slip translates to reduced rotor losses, hence higher efficiency,” Rajagopalan said.
Ferrite magnets for efficiency
Permanent magnet motors offer higher efficiency than induction machines—and maintain their efficiency over a wide torque/speed range, but rare-earth PMs pose a cost challenge, noted John Petro, founder and CTO of NovaTorque Inc. The company’s initial design to develop a new IE4-plus efficiency motor was based on neodymium-iron-boron (Nd-Fe-B) magnets, but “we saw high cost of rare-earth magnets coming,” Petro said.
Instead, a PM motor with equivalent benefits was developed using less costly ferrite magnets, as described in Petro’s paper, “Exceeding IE4 efficiencies with cost-effective ferrite magnet PM motors.” However, the new design required compensation for the 3:1 lower power density of ferrite versus Nd-Fe-B magnets, explained Petro. An axial motor with conical air gap, allowing for flux concentration and a special stator design contributed to obtaining 91.7% efficiency at 20 Nm output at 1,800 rpm—as well as 93% efficiency for a smaller motor capable of 10 Nm output at 1,500 rpm (see diagram).
The design is scalable upward (more easily) or downward for motor size, Petro explained. Commercial availability of these motors is pending.
Ferrite PM Motor
Source: NovaTorque Inc.
Efficiencies for NovaTorque’s motors indicated above include that of the drive, since PM motors can’t be run directly on line. One tradeoff with this design is a substantially heavier motor due to larger mass of ferrite magnet needed.
Updating, harmonizing standards
“New EU-mandate & IEC 60034-30 energy classes” by Martin Doppelbauer, Prof. at Karlsruhe Institute of Technology, Germany, updated developments concerning the major multi-part International Standard IEC 60034. Latest (2nd) edition of standard’s part 30 (IE code classes) has been approved; parts 30-2-1 (motor efficiency measurement and testing) and 30-2-3 (harmonic loss testing due to converter power supplies) are slated for approval in 2012 or 2013.
IE4 motor efficiency class is now formally included in the 2nd edition of IEC 60034-30 standard. A still higher IE5 class has been proposed but no qualifying commercial motor is available, according to Doppelbauer. However, such a motor is envisioned to be able to lower losses by 20% compared to IE4 class.
Motor size range covered in IEC 60034-30 has been widened to now include the range of 0.12-500 kW, for 50 Hz units. Higher power ratings up to 800 kW will have flat efficiency limits. More motor types are now included: all fixed-speed, wound-rotor synchronous, single-phase designs, and virtually all brake motor types; as well as variable-speed PM synchronous motors, within the speed range of 1,000-5,000 rpm. To avoid loopholes, operating cycle and temperature range definitions, among others, have been tightened in the latest version of IEC 60034-30.
Switched reluctance, dc motors, and electronically commutated motors are not formally part of the standard but can be included if tested for efficiency with a drive. Future standards will cover this issue.
Upcoming standards will also look at line-fed versus converter-fed motors. The latter include the effect harmonic losses due to the drive and will need an efficiency assessment to factor-in use of a sine filter. IEC 60034-2-3 will look at test methods for determining losses and efficiency of converter-fed motors using VSDs. Future standards will address increasingly wider systems. One example is IEC 528xx, which will cover efficiency of VDSs, power drive systems, and complete drive systems, Doppelbauer noted.
In “Harmonized standards for motors & systems: global progress report and outlook,” Conrad U. Brunner—A+B International and operating agent for 4E EMSA—summarized various accomplishments of energy-efficiency organizations and companies. Brunner cited continued global expansion of MEPS with coverage accounting for approximately 45% of electricity generation and about 70% of electricity usage. Standard operating conditions have also been more specifically defined for motor output, operating losses, life span, and load factor, among others.
Overall, fewer exception to motor standards are now allowed; for example, explosion-proof and gear motors, brakes, and operation at >40 C and higher than 1,000 m elevation. Harmonized testing for motor efficiency has been approved. “The 2012 revision of IEC 60034-2-1 will have one preferred test method for motors up to 1 MW output,” Brunner emphasized.
A new RFID tag has been specified to allow tracking of individual IE-class motors. This is in addition to the name plate that shows efficiency class and nominal efficiency in conformance with European Ecodesign requirements.
Brunner summarized what’s needed from energy-efficiency providers to spur further gains:
- Help OEMs understand life-cycle cost
- Include variable load efficiencies in MEPS
- Develop system MEPS (for pumps, fans, compressors, etc.)
Since its inception in 1995, EEMODS has been staged in Europe, Asia, and now in North America. The next, 8th edition in 2013 will be held in Rio de Janeiro, Brazil.
See related article:
Frank J. Bartos, P.E., a Control Engineering contributing content specialist. Reach him at braunbart(at)sbcglobal.net.
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