Copper in energy efficient motors

The high [[electrical conductivity]] of [[copper]] is an important design factor that helps to improve the energy efficiency of [[motors]]. This is important because motors and motor-driven systems are very significant consumers of [[electricity]], accounting for 43%-46% of all global electricity consumption and 69% of all electricity used by industry.<ref name=Waide>Energy‐efficiency policy opportunities for electric motor‐driven systems, International Energy Agency, 2011 Working Paper in the Energy Efficiency Series, by Paul Waide and Conrad U. Brunner, OECD/IEA 2011)</ref>

Inefficient electric motors waste electrical energy. Since most electricity is generated from [[Fossil-fuel power station|fossil-fueled power plants]], motors and motor-driven systems are indirect contributors to [[greenhouse gas emissions]] produced by these plants. Hence, there are compelling economic and environmental reasons to increase the use of energy efficient motors.

This article discusses how copper helps to improve the electrical energy efficiencies of motors. The advantages of copper as an [[electrical conductor]] in the [[stator]] and [[Rotor (electric)|rotor]] are discussed, as is a new copper [[die-casting|die-cast]] rotor technology that was developed specifically for [[premium efficiency]] motors. The article also introduces motor legislations implemented around the world that focus on energy savings and reduced [[carbon footprint]]s that can be achieved with energy-efficient motor systems. The article focuses on [[Induction motor|AC induction motors]] because they are frequently specified to power industrial machinery.

==Electric motors transform electrical energy into mechanical energy==
An [[electric motor]] is an [[electromechanical]] device that uses [[magnetic attraction]] and repulsion to produce controlled [[rotational motion]]. In an electric motor, [[electrical energy]] delivered by a [[power source]] is converted into [[mechanical energy]]. This is accomplished when one set of [[electromagnet]]s mounted on a fixed assembly (or [[stator]]) attract the opposite polarity of electromagnets on a rotating assembly (or [[Rotor (electric)|rotor]]). The [[magnetic field]] produced by the stator rotates in space by the application of an electric current, thereby causing the rotor to rotate with it. In turn, the rotor drives mechanical loads coupled with it.

By transforming [[electrical energy]] into [[mechanical energy]], electric motors are able to power a wide range of [[machinery]] and consumer products.

==Electrical motor efficiency==
Motors and motor driven systems are huge consumers of [[electricity]]. They are estimated to account for 43%-46% of all global electricity consumption as well as 69% of all electricity used by industry.<ref name=Waide />

Since most electricity is generated from [[Fossil-fuel power station|fossil-fueled power plants]], motors and motor driven systems are, in an indirect sense, major contributors to [[greenhouse gas]] emissions produced by these plants.

Electric motors do not transfer 100% of the input electrical energy into [[kinetic energy|kinetic mechanical energy]]. A certain percentage of electrical energy is “lost” during the conversion to mechanical energy. These losses, which are manifested as electrical power losses ([[waste heat]] due to the electrical resistance of the [[Coil|windings]], conductor bars and end rings), magnetic core losses, stray load losses, mechanical losses, and brush contact losses, reduce what is known as the “[[Premium_efficiency#Definition_of_motor_efficiency|energy efficiency]]” of motors. The electrical power losses account for more than half of a motor’s total losses.<ref name=CD-ROM>{{cite web|title=High efficiency motors and transformers CD-ROM # A6121|work=Electrical: Energy Efficiency|publisher=Copper Development Association Inc.|accessdate=20 March 2012|url=http://www.copper.org/publications/pub_list/energy_efficiency.html}}</ref>

This is a problem for several reasons. First, inefficient electric motors waste electrical energy, thereby increasing electrical demand and associated electricity costs required to power motors. Second, when electricity is generated by oil- or coal-fed power plants, the burning of [[fossil fuel]]s produces [[carbon footprint]]s from the usage of [[natural resources]] and the emissions of [[greenhouse gases]]. Electrical energy losses from inefficient motors, therefore, waste precious [[natural resources]], cause increased emissions of [[greenhouse gases]], and increase [[operating cost]]s (i.e., increases utility bills). Third, [[waste heat]] from inefficient motors increases maintenance and decreases the life of the motor.

For these reasons, there are compelling economic and environmental needs to evaluate the benefits of energy efficient and [[Premium efficiency#Premium efficiency electrical motors|premium efficiency electric motors]] versus their standard counterparts.

===Increasing the electrical energy efficiencies of motors===
Until the energy crises in the 1970s, most general-purpose motors were designed to provide rated output and operating characteristics at reasonable cost. Efficient operation was at best a secondary consideration. As energy prices began to rise, manufacturers began to develop improved motors known as "high-efficiency" and "energy-efficient".<ref>{{cite web|url=http://www.copper.org/applications/electrical/energy/motor_text.html|title=Introduction to Premium Efficiency Motors|publisher=Copper Development Association Inc.|accessdate=20 March 2012}}</ref>

A well-designed motor can convert over 90% of its input energy into useful power for decades.<ref>{{cite web|title=Motors|publisher=American Council for an Energy-Efficient Economy|url=http://www.aceee.org/topics/motors|accessdate=20 March 2012}}</ref> When the efficiency of a motor is raised by even a few percentage points, the savings, in [[kilowatt hour]]s (and therfore in cost), are enormous. For example, it has been estimated that if all countries adopted best [[Minimum Energy Performance Standard]]s (MEPS) for industrial electric motors, by 2030 approximately 322 [[terawatt]]-hours of annual electricity demand would be saved. As an additional environmental benefit, this savings in electric demand corresponds to a saving of 206 million tons of [[Carbon dioxide emissions|CO₂ emissions]].<ref name=Waide />

The electrical energy efficiency of a typical industrial induction motor can be improved by: 1) reducing the electrical losses in the [[stator]] windings (e.g., by increasing the cross-sectional area of the conductor, improving the winding technique, and using materials with higher [[electrical conductivity|electrical conductivities]]), 2) reducing the electrical losses in the rotor coil or casting (e.g., by using materials with higher electrical conductivities), 3) reducing magnetic losses by using better quality magnetic steel, 4) improving the aerodynamics of motors to reduce mechanical windage losses, 5) improving bearings to reduce friction losses, and 6) minimizing manufacturing tolerances.<ref name=Bloomsbury>The emerging electrical markets for copper, Bloomsbury Minerals Economics LTD, July 6, 2010</ref>

In addition to energy savings, other benefits of high efficiency motors over standard motors include: 1) cooler operating temperatures due to lower heat generation, resulting in lower maintenance and a longer life, 2) improved tolerance to voltage variations and [[Harmonics (electrical power)|harmonics]], 3) extended manufacturers’ warranties, and 4) rebates and tax incentives in some regions from utilities and municipalities.

===Tools to evaluate motor efficiencies and lifetime costs===
As part of its initiative to enhance the efficiency of motors, the [[United States Department of Energy]] created a free online computer [[software]] tool to help motor purchasing agents make informed buying decisions over the entire lifecycle of motors under consideration. The software, called MotorMaster+,<ref>{{cite web|title=MotorMaster+ International|publisher=U.S. Department of Energy|work=Advanced Manufacturing Office|url=http://www1.eere.energy.gov/manufacturing/tech_deployment/software_motormaster_intl.html|accessdate=20 March 2012}}</ref> contains data on 25,000 different motors. The software helps buyers select a motor based on list price, motor efficiency, payback analysis, and return on investment. It also enables an organization to examine its motor population or any individual motor as part of an overall repair and replacement plan.

By selecting any two motors and inputting unit energy costs and usage profiles, the software calculates [[life cycle cost analysis]] and [[greenhouse gas emissions]] reductions from using premium motors versus standard motors. Older operating motors with low efficiencies can also be evaluated for replacement. These motors cannot be rewound to exceed their original electrical efficiency design standards.

Another free tool, called MotorSlide Calculator™, can help calculate approximate annual savings in choosing a [[National Electrical Manufacturers Association]] (NEMA)<ref>{{cite web|publisher=The Association of Electrical Equipment and Medical Imaging Manufacturers|title=NEMA Premium Motors|url= http://www.nema.org/gov/energy/efficiency/premium|accessdate=20 March 2012}}</ref> premium electric motor (or any level of efficiency) versus a lower efficiency model.<ref group=Note>[http://www.productiveenergy.com/calculator/motorslide1.asp Online Motor Slide Calculator] from Productive Energy Solutions, LLC</ref>

==AC electric induction motors==
Motors have evolved into a variety of types according to user requirements, design, and production costs. Examples include: [[AC motor]]s, including AC [[induction motor]]s; [[DC motor]]s; and [[Universal motor|universal motors]]. Of these major categories of motors, there are many types (see [[Electric motor#Categorization of electric motors|Categorization of electric motors]] for a good introduction about various types of motors.)

This section will address copper in energy-efficient alternating current (AC) [[induction motor]]s because these types of motors are widely used in industrial drives.

The main parts of an [[induction motor|AC induction motor]] are the fixed housing body ([[stator]]), a rotating assembly ([[Rotor (electric)|rotor]]), and [[electromagnet]]s consisting of coils of [[Copper wire and cable|copper]] or [[aluminium wire]] around a core of magnetic steel.

Copper and aluminium can both be used in the stator coils, although copper coils are the standard as they are more flexible and they enhance motor [[Electrical efficiency|electrical efficiencies]] due to their higher [[electrical conductivity]]. In standard induction motors, instead of being wound in coils, the rotor conductors are [[Die casting|die-cast]] in the shape of a [[Squirrel-cage rotor|squirrel cage]] within a core of magnetic steel. Aluminium die-cast rotors are the standard material but copper die-casting of rotors is an improved new technology that is increasingly used to enhance motor energy efficiency. Induction motors can be designed with wound-rotor motors instead of a squirrel-cage. In a wound-rotor motor, the rotor winding is made of many turns of insulated wire.<ref>{{cite web|title=Wound rotor induction motors|work=All About Circuits|url=http://www.allaboutcircuits.com/vol_2/chpt_13/8.html|publisher=Sunstone Circuits|accessdate=20 March 2012}}</ref><ref>{{cite web|title=Wound rotor induction motor|work=Fundamentals of Power Engineering|url=http://www.ee.lamar.edu/gleb/power/Labs/Lab%2013%20-%20Wound%20rotor%20induction%20motor.pdf|accessdate=20 March 2012}}</ref><ref>{{cite web|title=Electric motors|work=Encyclopædia Britannica. Encyclopædia Britannica Online|publisher=Encyclopædia Britannica Inc.|date=2010|url=http://www.britannica.com/EBchecked/topic/182667/electric-motor/45824/Construction-of-induction-motors#toc45827|accessdate=20 March 2012}}</ref>

Other advantages to using copper rather than aluminium in AC motors include:<ref name=Waide />
* Lower [[coefficient of expansion]] for copper: aluminium will creep and move approximately 33% more than copper.
* Higher [[tensile strength]] for copper: copper is 300% stronger than aluminium and thus able to withstand high [[centrifugal force]] and the repeated hammering from current‐induced forces during each start.
* Higher [[melting point]] of copper: copper can better withstand thermal cycling over the life of the motor.

==Electrical conductivity in motor coils==

An electric current running through a simple straight wire creates a magnetic field defined by [[Ampère's_circuital_law|Ampere's Law]], but the field is relatively weak. Current running through insulated [[Copper wire and cable|copper]] or [[aluminium wire]] wound into a [[helix]] creates much stronger magnetic fields that causes a motor to turn.<ref>{{cite web|title=Contracting Helix|work=National High Magnetic Field Lab|url=http://www.magnet.fsu.edu/education/tutorials/java/contractinghelix/index.html|publisher=National High Magnetic Field Laboratory|accessdate=20 March 2012}}</ref>

To increase the strength of the magnetic field further, the coil can be wound from a longer length of wire and/or from a thicker diameter wire. Winding the coil around a cylinder of soft [[iron]] or other [[Ferromagnetism|ferromagnetic]] material can magnify the magnetic field by a factor of about 300 in common materials.

While the cylinder, commonly referred to as a “core,” magnifies the magnetic field, it is the coil that creates the field. The more wire in the coil (or coils), the stronger the magnetic field. The higher the electrical conductivity of the coil material, the stronger the magnetic field. The stronger the magnetic field, the more powerful the motor.

Electrical conductivity is a key operating parameter in determining which type of material to use in a motor’s coil. Wires made from better electrical conductors result in a more efficient transfer of electrical energy into mechanical energy. Poorer conductors generate more heat when transferring electrical energy into mechanical energy. In essence, more energy is wasted as the electrical resistance of the coil increases.<ref name=eurocopper>{{cite web|url=http://www.eurocopper.org/copper/electricmotors.html|title=Electric Motors (for 14 to 16 year-olds)|work=Physics - Electric Motors|publisher=European Copper Institute|accessdate=20 March 2012}}</ref>

[[Silver]] has the highest electrical conductivity of all metals (6.30×10^''7'' [[Siemens (unit)|siemens]]/meter at 20°C). However, silver is an expensive [[precious metal]] and is therefore not considered as a coil conductor material for motors.

[[Copper wire and cable|Copper]] has the second highest electrical conductivity of all metals (5.96 × 10^''7'' [[Siemens (unit)|siemens]]/meter at 20°C) and is much more affordable. Copper is commonly used in motors, including the highest quality motors because of its high electrical conductivity. Copper is an excellent metal to use for a motor's coils because: 1) it has less electrical resistance than almost any other non-precious metal; 2) it is easily made into wires; 3) it is not too expensive; 4) it can perform and survive at high temperatures; and 5) it can easily be recycled when the motor needs to be replaced.<ref name=eurocopper />

[[Gold]] is the third highest electrically conducting material (4.52 × 10^''7'' [[Siemens (unit)|siemens]]/meter at 20°C). Gold is an extremely expensive precious metal so it is not considered as a conductor material in motors.

The fourth highest electrically conducting material is [[aluminium]]. Aluminium has a much lower electrical conductivity than copper (3.5 × 10^''7'' [[Siemens (unit)|siemens]]/meter at 20°C) but is used in motors due to its lower cost.

===Copper coils increase motor electrical energy efficiencies===

Copper’s greater conductivity versus other materials enhances the electrical energy efficiency of motors.<ref name="engineerlive">{{cite web|title=IE3 energy-saving motors, Engineer Live|url=http://www.engineerlive.com/Design-Engineer/Motors_and_Drives/IE3_energy-saving_motors/22687/|publisher=Engineerlive.com|accessdate=2012-11-07}}</ref><ref name=Engineers /><ref name="drives">{{cite web|title=Ultra efficient motors have copper rotors; Drives and Controls|date=April 2006|url= http://www.drives.co.uk/fullstory.asp?id=978|publisher=Drives.co.uk|accessdate=2012-11-07}}</ref> For example, to reduce load losses in continuous-use induction-type motors above 1 horsepower, manufacturers invariably use copper as the conducting material in windings. Aluminium, because of its lower electrical conductivity, may be an alternate material in smaller horsepower motors, especially when the motors are not used continuously.

In general, older, standard-efficiency motors have higher losses than [[premium efficiency|premium motors]] that meet more current energy standards.<ref name=CD-ROM /> &nbsp;One of the design elements of premium motors is the reduction of heat losses due to the electrical resistance of the conductors. To improve the electrical energy efficiencies of induction-type motors, one design consideration is to reduce load loss by increasing the cross section of the copper coils. Increasing the mass of copper in a coil increases the electrical energy efficiency of the motor.

A high efficiency motor has more copper in the stator winding than its standard counterpart. For example, a 10 [[horsepower]] [[premium efficiency]] motor uses up to 75% more copper than a similar-sized motor with a standard efficiency.

For these reasons, early developments in motor efficiency focused on reducing electrical losses by increasing the packing weight of stator windings. This made sense since electrical losses typically account for more than half of all energy losses, and stator losses account for around two‐thirds of electrical losses.<ref name=Bloomsbury />

==Copper die-cast rotors==

The [[rotor (electric)|rotor]] is the rotating part of the motor. Rotor losses, an important form of power losses in induction motors, are largely but not entirely proportional to the square of the [[Induction_motor#Slip|slip]] (slip is the difference between the rotational speed of the magnetic field and the actual rpm of the rotor at a given load). Thus, rotor losses are reduced by decreasing the degree of slip for a given load. This is accomplished by increasing the mass of the rotor conductors (conductor bars and end-plates) and/or increasing their conductivity, and to a lesser extent by increasing the total magnetic field across the air gap between rotor and stator.<ref name=CD-ROM />

The electrical efficiency of motors can be improved by replacing the standard aluminium electrical conductor in the motor rotor with copper, which has a much higher electrical conductivity. Until recently, [[die-casting|die-cast]] motor rotors were produced only from aluminium while researchers worked on solving technological issues with copper pressure die-casting. Today, copper pressure die-casting is a proven technology and thousands of die-cast copper motor rotors are produced annually for motor applications where energy savings are prime design objectives.<ref>''Systematic Design Approach for a New Series of Ultra‐NEMA Premium Copper Rotor Motors'', by Fuchsloch, J. and E.F. Brush (2007), in EEMODS 2007 Conference Proceedings, 10‐15 June, Beijing.</ref><ref>{{cite web|title=Copper Motor Rotor Project, by the Copper Development Association|url= http://www.copper.org/applications/electrical/motor-rotor|publisher=Copper.org|accessdate=2012-11-07}}</ref>

The use of copper in place of aluminium for conductor bars and end rings of induction motor rotors results in improvements in motor energy efficiency due to a significant reduction in I^''2''R losses. Motor modeling by a number of manufacturers has demonstrated that motors with copper rotors yield overall rotor loss reductions from 15 to 20% compared to aluminium.<ref>{{cite web|title=Technology transfer report: The die-cast copper motor rotor; by the Copper Development Association Inc. and the International Copper Association Ltd|url=http://www.copper.org/applications/electrical/motor-rotor/pdf/technology_transfer_report.pdf|publisher=Copper.org|accessdate=2012-11-07}}</ref><ref name="drives" />

The advantages of motors with copper motor rotors on an equivalent basis with aluminium include the following:
* Motors have longer lives: they generate less heat and reduce thermal stresses, including those on insulation, which enable them to operate longer.<ref>{{cite web|title=Insulation system thermal life expectancy vs. total operating temperature, Marathon Electric-Generators|url=http://www.marathonelectric.com/generators/docs/manuals/thermal-life.pdf|publisher=Marathonelectric.com|accessdate=2012-11-07}}</ref><ref>{{cite web|title=Motor temperature ratings, The Cowern Papers|url=http://www.motorsanddrives.com/cowern/motorterms4.html|publisher=Motorsanddrives.com|accessdate=2012-11-07}}</ref>
* Motors are smaller: the increased electrical conductivity of the copper rotor material plus the need for a smaller volume of steel enables the motors to be shorter in length.
* Motors have 1‐5% higher energy efficiency ratings, so therefore consume less energy.<ref name=Bloomsbury />
* Motors have lower overall manufacturing costs.<ref name=Bloomsbury />

Currently, market penetration of copper rotor motors is mainly in low-voltage industrial motors ranging from {{nowrap|1 - 100 kW}}. There is a potential market for copper rotor motors in small fractional horsepower applications, but this has not yet come to fruition.<ref name=Bloomsbury />

In the U.S., a growing number of commercially available, general-purpose induction motors with die-cast copper rotors exceed [[National Electrical Manufacturers Association]] (NEMA) [[premium efficiency]] standards and display at least 10% lower total electrical losses than an average NEMA Premium® motor of the same size, as defined by US Department of Energy’s MotorMaster+ software tool (see: [[Copper in energy efficient motors#Tools to evaluate motor efficiencies and lifetime costs|Tools to evaluate motor efficiencies and lifetime costs]]).

For example, ultra-efficient motors up to {{nowrap|15 kW}} exceed NEMA Premium® standards.<ref>{{cite web|title=Low voltage AC motors, Siemens AG, "Industry leading, die cast copper rotors are available, 1-20 HP with GP, SD and IEEE841 motors, offering efficiencies higher than NEMA Premium® requirements|url=http://www.industry.usa.siemens.com/drives/us/en/electric-motor/nema-motors/Literature-and-technical-resources/Documents/NEMA%20Sel-Price%20Guide%202012.pdf|publisher=Industry.usa.siemens.com|accessdate=2012-11-07}}</ref> This was achieved by combining low resistive (I²R) losses of high-conductivity copper [[Squirrel-cage rotor|squirrel]] cages with optimized stator designs.

Two series of high-efficiency motors with copper rotors are offered by a German manufacturer<ref>{{cite web|title=SEW Eurodrive|url= http://www.seweurodrive.com/|publisher=Seweurodrive.com|accessdate=2012-11-07}}</ref> whereas a French manufacturer<ref>{{cite web|title=FAVI S.A., in Hallencourt, France|url=http://www.favi.com/download.php?fich=rotor/Plaquette+-+ang.pdf|publisher=Favi.com|accessdate=2012-11-07}}</ref> produces die-cast copper rotors for a wide variety of applications and manufacturers.<ref>{{cite web|title=MachineDesign.com; Copper shines in motor rotors|date=August 18, 2009|url=http://machinedesign.com/article/copper-shines-in-motor-rotors-0818|publisher=Machinedesign.com|accessdate=2012-11-07}}</ref><ref>{{cite web|title=Grundfos Producing Motor Rotors on Machines that use JVL Step Motor Drivers|url=http://www.jvl.dk/default.asp?Action=Details&Item=490|publisher=Jvl.dk|accessdate=2012-11-07}}</ref><ref>{{cite web|title=Ultra efficient motors have copper rotors (mentions Electrolux); Drives & Controls|url=http://www.drives.co.uk/fullstory.asp?id=978|publisher=Drives.co.uk|accessdate=2012-11-07}}</ref><ref>{{cite web|title=Super-efficient motors with copper rotors enter U.S. market; CDA news release|date=April 12, 2006|url=http://www.copper.org/applications/electrical/motor-rotor/pdf/SiemensNAMarketEntry.pdf|publisher=Copper.org|accessdate=2012-11-07}}</ref>

Also, the [[U.S. Army]] now employs {{nowrap|520 volt}} AC induction motors with die-cast copper rotors on a hybrid drive system on each axle of its severe-duty trucks. This has resulted in fuel economy increases of up to 40%.<ref>{{cite web|title=Die-cast copper rotors as strategy for improving induction motor efficiency; IEEE Xplore digital library|url=http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F4548154%2F4562569%2F04562636.pdf%3Farnumber%3D4562636&authDecision=-203|publisher=Ieeexplore.ieee.org|accessdate=2012-11-07}}</ref><ref>{{cite web|title=Copper motor rotors give Army trucks a boost; Machine-Design.com|date=March 8, 2007|url= http://machinedesign.com/article/copper-motor-rotors-give-army-trucks-a-boost-0308|publisher=Machinedesign.com|accessdate=2012-11-07}}</ref><ref>{{cite web|title=Copper rotors boost hybrid truck efficiency by 40%, Drives & Controls|date=February 2007|url=http://www.drives.co.uk/fullstory.asp?id=933|publisher=Drives.co.uk|accessdate=2012-11-07}}</ref>

Several motor models with cast aluminium rotors also exceed NEMA Premium® efficiencies. These models are considered by some to be not as advantageous as copper rotor models because they require more material in the stator.<ref name=CD-ROM /><ref>{{cite web|title=Optimization of motor design; Copper Development Association Inc.|url=http://www.copper.org/applications/electrical/motor-rotor/process_01.html|publisher=Copper.org|accessdate=2012-11-07}}</ref> Also, copper rotors enable designs with higher efficiency levels than NEMA Premium® (i.e., the so called "NEMA Super-premium" and beyond).

To optimize the electrical conductivity of copper die-cast rotors, it is necessary to use copper alloys with very low levels of [[impurities]]. Even low levels of most impurity elements will significantly increase the electrical resistivity of copper. Alloys C10100 (99.99% Cu, 0.0003 P, 0.0010 Te) and C11000 (99.90% Cu, 0.04% O) are recommended for die-casting copper rotors. Both these alloys have electrical conductivities of 101% International Annealed Copper Standard (IACS).<ref>{{cite web|title=Select copper material: Composition, purity, and alloying elements|url= http://www.copper.org/applications/electrical/motor-rotor/process_02_21.html|publisher=Copper.org|accessdate=2012-11-07}}</ref>

{| class="wikitable"

|+Alloys recommended for [[die-casting]] copper rotors<ref>{{cite web|title=Optimization of motor design: Copper metal properties|url=http://www.copper.org/applications/electrical/motor-rotor/process_01_11.html|publisher=Copper.org|accessdate=2012-11-07}}</ref><ref group=Note>[http://www.copper.org/applications/electrical/motor-rotor/process_10.html Information regarding the melting and pouring of copper metal into die-casting machines for copper motor rotors] from The Copper Development Association Inc.</ref>

! Parameter !! Copper alloy C10100 !! Copper alloy C11000
|-
| [[Electrical conductivity]] || 101% IACS || 101% IACS
|-
| [[Electrical resistivity ]] || 17.1 nΩ•m || 17.1 nΩ•m
|}

==Energy-efficient legislation impacting motors==
Manufacturers, in coordination with various manufacturing associations and in conjunction with voluntary government initiatives, have developed a wide range of motors with increased electrical efficiencies. At the same time, governmental and inter-governmental agencies seeking to achieve energy savings and reduce [[carbon footprint]]s from more efficient industrial motor systems have issued increasingly stringent standards and regulations requiring users to buy high- and premium-efficiency motors (over various time horizons) instead of standard efficiency alternatives for many applications.

Initiatives exist for nations to move towards [[Minimum Energy Performance Standard]]s (MEPS) for motors. In 2002, five nations adopted MEPSs. By 2011, thirty nine nations (the EU-27, as well as the U.S., Canada, Brazil, Mexico, Costa Rica, China, Korea, Taiwan, Australia, New Zealand, Israel, and Switzerland) will have adopted some form of mandatory MEPS for three-phase electric motors. Motors in these countries account for 70% of global electricity use in motor systems.<ref>Presentation by Conrad Brunner, A+B International, at EEMODS 2011, 13 September 2011, slide 18</ref> If the mandatory MEPSs in these 39 countries were raised to best-practice levels, savings could approach 206 million tonnes of [[carbon dioxide emission|CO₂ emission]]s annually by 2030.<ref name=Waide />

A summary of the worldwide standards of energy efficient motor programs is available.<ref>{{cite web|title=Energy efficient programs; WEG presentation|url=http://www.weg.net/green/_files/Energy-Efficiency-Global-Directives_-_Presentation.pdf|publisher=Weg.net|accessdate=2012-11-07}}</ref> Highlights of motor laws in the U.S. and E.U. are presented below.

===Motor laws in the U.S.===
In the U.S., the combination of [[Minimum Energy Performance Standard]]s (MEPS) by [[Energy Policy Act of 1992]] (known as EPAct 92) and voluntary labeling by [[National Electrical Manufacturers Association|NEMA]] has proved successful.

[[Energy Policy Act of 1992|EPAct 92]] was the first major energy law to require minimum, nominal, full-load motor efficiency ratings for most industrial motors. It set minimum efficiency levels for [[electric motor]]s.<ref>{{cite web|title=American Council for an Energy-Efficient Economy; see Motors page|url=http://www.aceee.org/topics/motors|publisher=Aceee.org|accessdate=2012-11-07}}</ref>
The motors, which came to be known as “EPAct motors”, are still commercially available. Their nominal efficiencies are between one and four percentage points higher than those of the so-called “standard-efficiency motors” that had dominated the market for decades.

The Consortium for Energy Efficiency<ref>{{cite web|title=The Consortium for Energy Efficiency; CEE Forum|url=http://www.cee1.org|publisher=Ceel.org|accessdate=2012-11-07}}</ref> (CEE) and the [[National Electrical Manufacturers Association]] (NEMA) agreed on a joint specification defining a "premium" efficiency motor. Motors meeting minimum specifications are eligible to carry the NEMA Premium® designations. Publications are available that compare NEMA Premium efficiencies versus EPAct minimums.<ref>{{cite web|title=NEMA Premium motors become the minimum efficiency required in December 2010; Copper Development Association, Inc.|url= http://www.copper.org/applications/electrical/energy/motorad_oct01.html#1|publisher=Copper.org|accessdate=2012-11-07}}</ref>

In 2005, the [[Energy Policy Act of 2005]] (EPAct 2005) established NEMA Premium® efficiency ratings as the basis for motor purchases by the federal government. NEMA Premium® motor efficiency ratings are up to several percentage points higher than those of their EPAct predecessors. This law broadened the size range to include motors from 1 to 500 hp.

Based on U.S. Department of Energy data, it is estimated that the NEMA premium-efficiency motor program would save 5.8 terawatt hours of electricity and prevent the release of nearly 80 million metric tons of carbon dioxide into the atmosphere over the next ten years. This is equivalent to keeping 16 million cars off the road.<ref>{{cite web|title=NEMA Premium motors; The Association of Electrical Equipment and Medical Imaging Manufacturers|url=http://www.nema.org/gov/energy/efficiency/premium|publisher=Nema.org|accessdate=2012-11-07}}</ref>

The [[Energy Independence and Security Act of 2007]] (Public Law 110-140, usually called “EISA 2007 Act”),<ref>{{cite web|title=Energy Independence and Security Act of 2007|publisher=U.S. Department of Energy|url=http://www.afdc.energy.gov/afdc/laws/eisa|accessdate=2012-11-07}}</ref><ref>{{cite web|title=An Overview of the Energy Independence & Security Act of 2007 (EISA)|publisher=ITB Inc.|url=http://www.ibtinc.com/artman/uploads/1/baldor_eisa_overview.pdf|accessdate=2012-11-07}}</ref><ref>{{cite web|title=The 2007 Energy Act: Good news for motor users; Copper Development Association|url=http://www.copper.org/applications/electrical/energy/energy_act_2007.html|publisher=Copper.org|accessdate=2012-11-07}}</ref><ref>{{cite web|title=Energy Independence and Security Act of 2007/Title III/Subtitle A#SEC. 313: Electric motor efficiency standards|url=http://en.wikisource.org/wiki/|publisher=En.wikisource.org|accessdate=2012-11-07}}</ref> the most recent law regulating motors, took effect in 19 December, 2010 and affects all new motors purchased after that date.<ref name=Engineers>{{cite web|title=Engineers: Restart your motor specifications - Federal minimum standards for nominal full-load motor efficiencies take effect for motors manufactured after Dec. 19, 2010|author=Michael Ivanovich and John Malinowski|url=http://www.csemag.com/index.php?id=1398&cHash=081010&tx_ttnews&#91;tt_news&#93;=23975|publisher=CFE Media|accessdate=20 March 2012}}</ref> Title III, Section 313 of the Act increases the mandated efficiency of electric motors in commercial and industrial applications and expands the range of motors to be regulated. Included in EISA is major provision for improving the minimum required energy efficiency in all integral horsepower motors.
EISA covers:
* 1-200 horsepower motors: The law eliminates EPAct level motors and requires that [[National Electrical Manufacturers Association]] (NEMA) premium efficiency level motors must be manufactured after December 19, 2010. These motors use more copper and steel than their less-efficient counterparts. Motors made prior to this date can still be sold and installed but manufacturers cannot make new motors less than the premium efficiency standard.<ref name=Engineers />

* 200-500 horsepower motors: The law requires minimum EPAct efficiency motors and advises that NEMA premium motors be considered for heavy duty cycle higher power cost applications.

* Other special purpose motors (e.g., (vertical pump motors) are included in the legislation as well.

Rebates may be available for premium efficient motors, depending on the project and its location (search the database [http://www.dsireusa.org here] for applicable rebates). &nbsp;A summary of the new EISA standards for motors can be found at: &nbsp;[http://www.nema.org/media/pr/20080327a.cfm NEMA Premium Efficiency Levels Adopted as Federal Motor Efficiency Performance Standards]. &nbsp;Further details about NEMA premium motors is available at: &nbsp;[http://www.nema.org/gov/energy/efficiency/premium NEMA Premium Motors]

===Motor laws in the E.U.===
Up to 2010, the E.U. had established voluntary programs, resulting in a significantly lower percentage of high efficiency motors on the market than in the U.S. A brief history of motor laws in the E.U. follows.

In 1998, the European Committee of Manufacturers of Electrical Machines and Power Electronics (CEMEP)<ref>{{cite web|title=European Committee of Manufacturers of Electrical Machines and Power Electronics|url= http://www.cemep.org/|publisher=Cemeo.org|accessdate=2012-11-07}}</ref><ref>{{cite web|title=Electric motors and variable speed drives|url=http://www.cemep.org/fileadmin/downloads/CEMEP_Motors_and_VSD.pdf|publisher=Cemeo.org|accessdate=2012-11-07}}</ref> issued a voluntary agreement of motor manufacturers on efficiency classification, with three efficiency classes: Eff 3 for Standard Efficiency, Eff 2 for Improved Efficiency, Eff 1 for High Efficiency. Two years later, the modern era of efficient motors in the E.U. began as the voluntary agreement between European Motor Manufacturer Association and the European Commission took effect.<ref name=Bloomsbury />

In June, 2005, the [[European Parliament]] adopted a Commission proposal for a Directive on establishing a framework for setting eco-design requirements (such as energy efficiency requirements) for all energy consuming products in the residential, tertiary and industrial sectors.<ref>{{cite web|title=Ecodesign for energy-using appliances; Europa: Summaries of EU legislation|url= http://europa.eu/legislation_summaries/other/l32037_en.htm|publisher=Europa.eu|accessdate=2012-11-07}}</ref>

The current, mandatory, efficiency level across a wide power rating range required of motors sold in Europe is embodied in the EU [[Minimum Energy Performance Standard]] (MEPS) scheme, introduced in July 2009.<ref name=Bloomsbury /> &nbsp;The EU MEPS not only raises the efficiency standard of motors sold in Europe, it also links Europe’s requirements to international standards. EU MEPS covers 2-, 4- and 6-pole single speed, three-phase induction motors in the power range 0.75 to 375 kW, rated up to 1000 V and on the basis of continuous duty operation.<ref name=Bloomsbury />

High efficiency motors (Eff1) represent only 12% of the market in the EU today.

==International standards for electric motor efficiency labeling==
A new international standard for electric motor efficiency labeling was introduced in 2008 (and revised in 2011) by the [[International Electrotechnical Commission]] (IEC). This standard, [[IEC 60034]]-30, defines energy efficiency classes for single-speed, three-phase, and 50 Hz and 60 Hz induction motors.<ref>{{cite web|title=IEC 60034-30 standard on efficiency classes for low voltage AC motors: Technical note; ABB|url=http://search.abb.com/library/Download.aspx?DocumentID=9AKK104295D4689&LanguageCode=en&DocumentPartID=&Action=Launch|publisher=Search.abb.com|accessdate=2012-11-07}}</ref><ref>{{cite web|title=Webstore: International Electrotechnical Commission (IEC)|url=http://webstore.iec.ch/webstore/webstore.nsf/Artnum_PK/41970|publisher=Webstore.iec.ch|accessdate=2012-11-07}}</ref><ref>{{cite web|title=Global efficiency standards for 3-phase AC motors; Specifications from IEC 60034-30|url=http://be2.sew-eurodrive.com/download/pdf/16900812.pdf|publisher=Be2.sew-eurodrive.com|accessdate=2012-11-07}}</ref> The standard is designed to unify motor testing standards, efficiency requirements, and product labeling requirements so that motor purchasers worldwide have the ability to easily recognize [[premium efficiency]] products. On 22 July 2009, Commission Regulation (EC) No 640/2009 implementing Directive 2005/32/EC stated that in the E.U., with a few exceptions for special purposes, drive motors shall not be less efficient than the IE3 efficiency level ([[premium efficiency]]) as of 1 January 2015.

Rotor losses in IE3 systems are considerably reduced by using copper instead of aluminium as the conductor material for the squirrel cage. The slip under load, which is proportional to the rotor losses, is significantly decreased compared with aluminium motors. Unlike aluminium motors, IE3 motors with a copper rotor do not require an increased amount of iron or need merely a moderate increase.<ref name="engineerlive" /><ref>{{cite web|title=IE3 motors ensure 10% efficiency increase, says NORD; Eureka: The site for engineering design|date=May 8, 2010|url= http://www.eurekamagazine.co.uk/article/26816/IE3-motors-ensure-10-efficiency-increase-says-NORD.aspx|publisher=Eurekamagazine.co.uk|accessdate=2012-11-07}}</ref> Other measures can also be taken to save energy in IE3 motors.

There is a 3‐4% energy efficiency difference between IE1 and IE3 standard motors, but the differences, and the absolute level of efficiency, depend on the output of the motor relative to its rating.

IE3 is a new classification, but one that has been recognized by NEMA in the U.S. It generally applies to large, industrial motors. In Europe, this grade of motor will only become mandatory in some applications in 2017. In the U.S., the required introduction date was 19 December, 2010 for larger motors; smaller motors will become mandated in 2017.

The U.S. and a few other countries have already introduced legislation requiring IE2 standard motors in certain applications. Many others have plans to introduce such rules. In Europe, IE2 became the obligatory standard on 16 June, 2011. For some motors, this is also true of China in 2011, although for other motors a minimum IE1 standard will be introduced in that year replacing earlier, less rigorous, requirements.

{| class="wikitable"
|+Comparison of International Motor Efficiency Standards<ref name=Bloomsbury />
! [[International Electrotechnical Commission]] / EN 60034-30 !! EU [[Minimum energy performance standard|MEPS]] !! CEMEP<ref>{{cite web|title=CEMP; European Committee of Manufacturers of Electrical Machines and Power Electronics|url=http://www.cemep.org/|publisher=Cemep.org|accessdate=2012-11-07}}</ref> (European voluntary agreement) !! [[Energy Policy Act of 1992|US EPAct]] !! Other, similar national regulations
|-
||IE3 Premium efficiency ||nowrap|IE3 Premium efficiency || ||Identical to NEMA Premium efficiency
|-
| IE2 High efficiency || IE2 High efficiency || Comparable to EFF1 || Identical to NEMA Energy efficiency/EPACT || Switzerland, Canada, Mexico, Australia, New Zealand, Brazil, China
|-
| IE1 Standard efficiency || || Comparable to EFF2 || Below standard efficiency || Switzerland, China, Brazil, Costa Rica, Israel, Taiwan
|}

A time table of minimum performance standards for the various motor efficiency levels in various countries is presented below:

{| class="wikitable"

! Efficiency levels !! "Mandatory" [[Minimum Energy Performance Standard]]s (MEPS) for industrial electrical motors!! "Voluntary" [[Minimum Energy Performance Standard]]s (MEPS) for industrial electrical motors
|-
|nowrap| Super premium (IEC Class 4) || Advocacy commenced || Advocacy commenced
|-
| Premium (IEC Class 3) || USA (2010), Canada (2010), Mexico (2010), EU (2015-2017), Japan (2015) || China (2011), Korea (2012), India (2014)
|-
| High (IEC Class 2) || ANZ (2006), Korea (2008), Brazil (2009), China (2011), EU (2011), Taiwan (2013) || India (2011)
|-
| Standard (IEC Class 1) || Available in Africa, Asia, Latin America, Europe || Available in Africa, Asia, Latin America, Europe
|-
| Below standard || Available in Africa, Asia, Latin America, Europe || Available in Africa, Asia, Latin America, Europe
|}

Once a consensus regarding the classification of the efficiency of motor driven systems is achieved, manufacturers and users can then move to create a labeling scheme. With time, legislation on standards may follow. For the present, though, legislation‐based installation of higher efficiency motors will be limited to stand alone motors.<ref name=Bloomsbury />

==Notes==
{{Reflist|group=Note}}

==References==
{{Reflist|30em}}

==External links==
* [http://www.motorsystems.org Electric Motor Systems (EMSA)]
* [http://www.aosmithmotors.com/uploadedFiles/AC-DC%20manual.pdf The AC’s and DC’s of Electric Motors, A.O.Smith]
* [http://www.copper-motor‐rotor.org/process_01.shtml Copper Development Association (2007), Copper Rotor Motor Project]
* [http://www.leonardo-energy.org/ Leonardo Energy: The Global Community for Sustainable Energy Professionals]
* [http://www.aceee.org/topics/motors/motor-book Energy-Efficient Motor Systems: ''A Handbook on Technology, Program, and Policy Opportunities'', 2nd EDition] (a definitive book on energy efficiency in motors) by the American Council for an Energy-Efficient Economy
* [http://www.cemep.org/ European Committee of Manufacturers of Electrical Machines and Power Electronics]
* [http://www.managenergy.net/resources/360 European Commission/Energy: Manage Energy]
* [http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:191:0026:0034:EN:PDF EC COMMISSION REGULATION No 640/2009; implementing Directive 2005/32/EC of the European Parliament and of the Council with regard to ecodesign requirements for electric motors]
* [http://www.aceee.org/topics/motors American Council for an Energy-Efficient Economy]; see Motors
* [http://www.nema.org/gov/energy/efficiency/premium/ NEMA Premium Motors]
* [http://www.motorsmatter.org/index.asp Motors Decisions Matter] This is a US-based public-awareness campaign that provides support for companies interested in motor management.

{{DEFAULTSORT:Copper in energy efficient motors}}

[[Category:Electric motors]]
[[Category:AC motors]]
[[Category:Energy conservation]]
[[Category:Energy policy]]
[[Category:Copper]]