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Efficiency becomes standard

Electric motor Minimum Energy Performance Standards (MEPS) are now well established across Australia. Yet on a global scale, the world of MEPS could be seen as disjointed and incomplete. New global standards, new directions and innovative research into total drive-train energy minimisation aim to remedy this situation.

The Australian introduction of Minimum Energy Performance Standards (MEPS) for electric squirrel-cage induction motors is, in some respects, old news. This Australian Greenhouse Office (AGO) initiative, which was first legislated in October 2001, represented an important first step for Australia. Since this inauguration, both the Australian and international MEPS scene have been anything but stagnant. A great deal of work has been–and continues to be–undertaken around the world to refine and enhance MEPS policy and rulings.

The 2001 MEPS legislation was set out in the Australian standard AS/NZS 1359.5-2000 Rotating electrical machines – General requirements Part 5: Three-phase cage induction motors – High efficiency and minimum energy performance standards requirements. This prescribed two ‘levels’ of performance for electric motors: ‘MEPS-efficiency’ (the minimum legal standard), and a ‘high efficiency’ (HE) level. At this stage, there was some alignment between the Australian ‘high efficiency’ (HE) and ‘MEPS-Efficiency’ levels with the European ‘EFF1’ and ‘EFF2’ levels.

In April 2006, the two Australian efficiency levels were ratcheted up a notch. A revised edition of the standard (AS/NZS1359.5:2004) saw the HE levels specified in AS/NZS 1359.5:2000 effectively become the new MEPS levels (often referred to as ‘MEPS2’, and aligned for two- and four-pole motors with the European ‘EFF1’), coupled with an entirely new, and more-stringent, ‘high efficiency’ (HE) level. This new HE level targeted a further 15 per cent reduction in losses on the 2001 MEPS ‘high efficiency’ (EFF1) levels.

MEPS2006 improves on the positive impact of MEPS2001. In the long-term, it should reduce total Australian energy consumption by 8900GWH, and cut the country’s greenhouse emissions by 7.7MT [4].

Clarifying the issues

With the introduction of MEPS2006, Australia is now one of the world leaders in regulating electric motor energy efficiencies. The ruling is mandatory and applies to all two-, four-, six- and eight-pole electric squirrel-cage induction motors ranging from 0.73 to 185kW. There is now wide industry acceptance of the standard, with the majority of Australian motor users specifying MEPS-compliant motors when purchasing.

On the downside, Australia’s position as a net importer of electric motors has meant that we have been exposed to some confusing messages in the market place. This stems from the current lack of direct ‘matching’ of motor efficiency standards throughout the MEPS world.

In Europe, the electric motor industry body–the European Committee of Manufacturers of Electrical Machines and Power Electronics (CEMEP)–defines two standards for electric motor: ‘increased efficiency’ EFF2 and the higher standard ‘high efficiency’ EFF1. These are currently voluntary requirements and are only specified for two- and four-pole motors ranging from 1 to 100kW. In the US, the Congress’s 1992 Energy Policy Act (EPAct) defined the ‘EPAct’ standard motor, and later (in 2004) the ‘NEMA premium’ standard. The lower standard EPAct motor is sometimes generically referred to as ‘high efficiency’. The US standards are mandatory, and apply to two-, four- and six-pole motors ranging from 0.75 to 150kW. Curiously, this standard applies to horizontal foot-mounted motors, providing loopholes that currently allow many US motors–for instance, flange mounted motors–to remain non-compliant.

This global mismatch causes problems. An example is the broad and ambiguous use of the term ‘high efficiency’. Australian MEPS2 (‘minimum efficiency’)-compliant motors are essentially equivalent, efficiency-wise, to European EFF1 and US EPAct motors. Both the latter are often referred to in their respective countries as ‘high efficiency’, yet AS/NZS1359.5:2004 defines ‘high efficiency’ as a much higher grade, equating to what other countries would refer to as ‘premium efficiency’. The domestic transition of our standards definition in 2006–where Australia’s ‘high efficiency’ standard was redefined as ‘MEPS-compliant’–has probably helped fuel this confusion.

Further confusion arises from the differing power ratings covered by the various international standards. For example, the Australian standard covers 0.75 to 185kW, while the European CEMEP agreement covers 1 to 100kW. This has lead to some confusion. For instance, some end users have specified EFF1 for 0.75kW motors, but while 0.75kW motors are covered by Australia’s ‘MEPS2’ standard, they do not fall under the European EFF1 definition.

Unfortunately, some less-than-ethical electric motor manufacturers have taken advantage of this definition confusion, to more positively position their product. The best and most straightforward path through this maze is to ensure that any motor under consideration is compliant with AS/NZS1359.5:2004, and falls into either the ‘MEPS’ or ‘high efficiency’ category according to this standard. In Australia, all motors coming under the scope of the AS1359.5:2004 must be registered for sale with state regulators. A full list of motors regulated and registered for MEPS can be found on the Government web site:

Harmonising the standards

The electric motor world suffers more inconsistencies in definitions and standards, most notably in the way that motor efficiencies are measured and benchmarked.

In simple terms, the energy losses that occur in electric motors can be broadly broken down into three categories:

• ‘Constant’ losses–Iron, friction/bearing and windage losses

• ‘Load’ losses–I2R losses in stator and rotor windings

• ‘Additional’ (or ‘stray’) losses–Losses produced by load current in active iron and non-conductor metal parts; eddy current losses in winding conductors.

In world-class electric motor designs, so-called ‘optimised motor design’ addresses these loss areas individually and in detail (see figure 1). Stator slot design is improved to achieve more copper in the stator slots, while winding geometry is changed to reduce stator resistance losses. Active material in both the stator and rotor are increased, while lamination steel quality is improved and thinner laminations used to reduce iron losses. Fan design is improved and low-friction bearings used to reduce friction and windage losses. In the rotor, copper can be used in place of aluminium, and slot design and end-ring design improved to reduce rotor resistance. The end result is a motor of superior efficiency.

It must be noted, however, that the increase in active material in motors with improved efficiency leads to physically larger motors for the same power rating. Manufacturers have tried to minimise this size increase by further optimising the design of motors and, for example, using copper as the rotor material instead of the more common, but higher resistance, aluminium.

Just how motor efficiency and losses–particularly the additional losses–are measured has, to-date, been a further source of global confusion. Until recent times, this confusion was reflected in the Australian Standard AS/NZS1359.102 Rotating Electric Machines — Methods For Determining Losses & Efficiency. The standard describes two methods of motor loss and efficiency testing: ‘Method A’ and ‘Method B’. Method A is based on the US standard IEEE 2B and IEC61972. It involves the accurate and direct measurement of the additional load losses. Method B is based on the old European IEC34-2 standard, and assumes a fixed 0.5 per cent for additional load losses. In effect, AS/NZS1359.102 has ‘a foot in both camps’.

In October 2007, this confusion began to clear with the publication of a new International Electrotechnical Commission (IEC) standard–IEC60034-2-1–which defines a number of efficiency and loss methods, each categorised according to the corresponding level of measurement uncertainty. This new standard, which is expected to be adopted globally, goes a long way towards harmonising global motor efficiency testing practices. While it will be up to each country to determine which method it will adopt, it is expected that here in Australia we will err towards the direct measurement method (equivalent to Test Method A), with the method of least uncertainty.

Similarly, the actual motor efficiency benchmarks are now being addressed on a global scale. A draft IEC standard (IEC 60034-30) proposes to harmonise motor efficiency levels into four distinct groups (see figure 2). Based on the test methods defined in IEC60034-2-1, this new standard will address induction motors from 0.75 to 370kW, in two-, four- and six-pole design and is expected to be published in 2009.

The upside of such global testing and benchmarking normalisation is the benefit to consumers of electric motors who play on a global stage, particularly large international corporations and OEMs. These groups will be able to purchase and rationalise motor stocks drawn from global sources, knowing that they comply with globally recognised standards. As a net importer of motors, this scenario would represent a big win for Australian users. The comparison of motor efficiency levels worldwide would be much clearer.

Beyond MEPS

Perhaps more exciting, is research and development work being undertaken by global industry bodies that goes beyond the bounds of the electric motor itself. This work is exploring the domain of what is often described as ‘total drive efficiency’.

While current MEPS-compliant electric motors realise a two to three per cent efficiency improvement over old ‘standard’ efficiency motors, it is valuable to see how such figures sit within the context of a total drive train efficiency upgrade. While MEPS compliance is vital, it is equally vital to look beyond the motor itself and consider the drive train as a whole.

Figures 3 and 4 depict a real-world example of such a total drive train efficiency upgrade, drawn from the Australian mining industry. The top-most illustration in Figure 3 shows the pre-upgrade conveyor head-drive installation of a very old system. Originally, the drive train comprised a MEPS-compliant motor, coupled to the head-drive via a vee-belt, worm-gear unit and chain/sprocket drive. The inherent efficiencies across the three-stage drive train resulted in an overall drive efficiency of 60.8 per cent.

A high efficiency helical-bevel gear unit, close coupled to the MEPS-compliant motor, replaced this inefficient drive train. The resultant efficiency of this replacement assembly was 88 per cent. Most important are the energy savings achieved as a result of this almost 30 per cent efficiency improvement. Based on an energy cost of $0.10/kWh, the new installation saves almost A$2500 per annum in reduced energy costs. The estimated return on investment in this particular scenario is around two to three years. There would also be a significant reduction in greenhouse gas emissions.

It should be noted that the average life expectancy of a typical induction motor can be around 20 years [1]. As a result, the energy savings determined here offer commercial benefits well beyond the ROI period.

More telling is just how this total drive train efficiency might vary if MEPS compliant motors were not used. Using a pre-2006 MEPS-compliant motor (non-compliant by today’s rulings), the total drive train efficiency with the close-coupled helical-bevel gear unit would only drop to 86 per cent. This figure is still significantly higher than the vee-belt/worm-gear/chain/sprocket combination with MEPS-compliant motor. This underscores the importance of looking beyond the motor itself, considering the entire drive train and using modern techniques in drive application.

A further consideration is the application of frequency inverter technology, used in conjunction with high efficiency electro-mechanical systems. Studies have shown that pumped flow regulation systems can achieve significant efficiency improvements by replacing traditional ‘single-speed pump plus throttle valve’ technology with a pump driven by a variable speed inverter [2]. This efficiency improvement can reduce energy consumption to a fraction of what would be required, if the pump speed regulation is coupled with high efficiency motors, pumps, couplings and piping systems.

Such ‘total drive efficiency’ perspectives are central to studies currently being undertaken by a wide range of influential industry groups and conferences. These include the European Commission’s Energy Usage Product Directive, the International Copper Association’s Energy Efficiency in Motor Drives Systems (EEMODS), and the Asia-Pacific Partnership on Clean Development and Climate (AP6) initiative. The latter is most important from an Australian environment perspective, as it represents the major industrial groups in our region: Australia, China, India, Japan, Korea and the United States.

Such industry groups are seeking out energy saving opportunities within specific electric motor application areas such as fans, pumps, HVAC, compressed air systems, refrigeration and so on. The results of such studies will pave the way for the future, and could represent the foundation for a new wave of global ‘total system MEPS’ standards.

Towards the future

The electric motor statistics that most clearly point the way for future developments are, surprisingly, those that talk more of the total life-cycle economics of the electric motor, rather than any resultant reduction in megatonnes of greenhouse gases. A 2007 study from the European Commission’s Energy Usage Product Directive notes that energy costs for an electric motor in continuous operation represents 96 per cent of its total life-cycle costs [1]. Capital cost of the motor itself represents just 2.5 per cent. This is largely because of the inherent robustness and longevity of the squirrel-cage induction motor–the same study pegs the motor’s average life at somewhere between 12 and 20 years.

This suggests that the performance-class of the electric motor–and the design of drive train to which it is coupled–need to be carefully selected and implemented. Initial capital expenditure will typically be a negligible factor in terms of total life-cycle expenditure. By contrast, the very nature of the technology applied, both at the motor level and across the total drive train, could have huge ramifications both environmentally and economically.

It is apparent that MEPS standards are now moving swiftly towards global harmonisation. In addition to the harmonising impacts of the IEC60034-2-1 global test methods and the IEC 60034-30 motor efficiency levels, the US targets a closing of its EPAct loopholes in around 2011, and Europe hopes to make EFF1 a mandatory motor requirement in the same year. The MEPS world is fast moving towards a uniform standard. The next major challenge will be to address total life-cycle/total drive train efficiency issues. This, then, is an important direction for electric motor MEPS development as we go forward.


[1] EUP Lot 11 Motors, Report No. 3, Analysis of existing technical and market information, ISR- University of Coimbra, Aníbal T. de Almeida et al, April 2007

[2] Motor Challenge – Energy Efficient Motor Driven Systems, European Copper Institute, April 2004

[3] Australia & New Zealand Standard AS/NZS 1359.5: 2004, Rotating electrical machines—General requirements. Part 5: Three-phase cage induction motors—High efficiency and minimum energy performance standards requirements

[4] Regulatory impact Statement for Minimum Energy Performance Standards for Electric Motors, Syneca Consulting, December 2003

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