Since 1 January 2015, rules governing the efficiency of new, low-voltage electric motors permitted for sale in the European Union have changed. Virtually all three-phase induction motors (two-, four- and six-pole) in the range 7.5–375kW must now be certified to IE3 (premium efficiency). Only applications running with a variable speed drive (VSD) are still allowed to source IE2 (high efficiency) motors – although there is a small list of exceptions, including for example ATEX (notified hazardous area) motors.
This is the second phase of EU MEPS (the European Minimum Energy Performance Standard), under European Commission regulation EC 640/2009 (amending Regulation EU 4/2014), and covers motors rated up to 1,000V. It supersedes the first phase of the scheme, implemented back in June 2011, which prescribed IE2 efficiency for motors with a rated output from 0.75 to 375kW. The next phase, on 1 January 2017, will extend the ruling to include motors down to 0.75kW – again with the proviso that IE2 be permitted for VSD-based applications.
Automation giant ABB is reminding engineers that existing IE2 motors do not have to be decommissioned and replaced, as the ruling is not retrospective. Furthermore, users' stocks of IE2 motors can still be used, despite the expired deadline. However, any new IE2 motors for any application – existing or new – will require a VSD. That said, ABB motors and generators business unit manager Dave Hawley advises that using VSDs not only delivers EU MEPS compliance, but also almost always results in massive energy cost reductions. Just as important, VSDs can enable more precise and reliable motor speed and torque control, and hence lead to improved production operations and flexibility, as well as product quality.
"While the energy-saving benefits of VSDs are well documented, the productivity improvements that can be achieved are less well publicised," comments Hawley. And dispelling myths around complexity of set-up, commissioning and operation, he also points to VSD features now more commonly available, such as pre-installed VSD configuration macros (particularly for pumps and fans), wiring error protection software, and intelligent control panels – designed to simplify operator interaction.
So much for the top level stuff: what do the new rules mean in more practical detail? What, for example, happens if operators purchase IE2 motors (available perfectly legally) but install them on applications not running under VSD control, in breach of the new regulations? Probably not a lot, given that the body policing such EU rules in the UK is the National Measurement Office, which will be focusing its attention on motor manufacturers and dealers selling the equipment, rather than engineering and procurement managers buying it. In some other member states that have no similar official body, it's hard to see how any enforcement might work. And there appears to be no prescribed penalty.
Drive or no drive?
Andy Glover, WEG's product manager for LV motors in Europe, makes the point that controlling what end users do with electric motors is nigh on impossible – particularly given that the vast majority of motors are sold into OEMs or via distributors. "We attach a CEMEP [European Committee of Manufacturers of Electrical Machines and Power Electronics] standard label which, for an IE2 motor, clearly states that it must be used with a drive. But in the end we can't oversee what they do."
WEG's solution is to "err on the side of caution" and maximise stocks of IE3 motors for sale. Others are taking slightly different approaches. Siemens, for example, last year launched new IE3 and IE4 (super-premium efficiency) induction motors – including its award-winning modular Simotics FD (flexible duty) range – based on the same frame sizes and shaft dimensions as its earlier IE2 units for easy retrofit.
Julijana Ristov, Siemens business manager for LV motors and drives, says these are now core, adding that the company no longer sells IE2 motors – other than by special arrangement with its factory. What's more, she adds that Siemens has maintained prices for IE3 electric motors at IE2 levels. "So why buy IE2 when you can get all the advantages of IE3 for the same money?" And she means not only the obvious energy savings, but also that the new motors are VSD-ready (as opposed to some older motors that suffered damage when used with inverters, due to inadequately insulated bearings).
Either way, the vast majority of reputable plants and factories will follow the rules – not just because of the risk to corporate reputations, nor even for the green advantages. The plain fact is that IE3 motors do save money. Looking at the numbers, a small 0.75kW machine (not mandated to IE3 until 2017) sees an improvement from 79.6% efficiency at IE2 to at least 82.5% to qualify for IE3 under IEC 60034-30-1 Ed 1.0 (2014). For a 30kW motor, IE2 requires 92.3% efficiency, while IE3 must offer a minimum of 93.6%. And for a large 160kW device, you're looking at 94.9% for IE2, rising to at least 95.8% for IE3.
Those differentials may not look huge, particularly on the larger machines. However, the latter are big power consumers and, if (only if) they're running near continuously over several years, small percentages coupled to the increased reliability associated with newer IE3 class motor designs, equate to very substantial savings. That's because, as ABB's LV motors product group manager Keimo Kalliosaari states, on average, motors consume 12–15 times their purchase price in electricity alone every 12 months.
Look at it this way: ABB calculates that a 45kW motor priced at £1,700 and running at 94.1% efficiency for 6,000 hours per annum will cost £2,105,454 over a 20-year lifetime (assuming realistic electricity pricing and downtime costs). That's around 1,175 times its purchase price. Which is why he suggests that users stop worrying about the upfront costs and remember what matters – total cost of ownership. "Think of motors' total costs as comprising 1% purchase price, 35–45% running costs and 45–55% the cost of not running," advises Kalliosaari.
ABB, Siemens and others all offer online ROI (return on investment) calculators that let you plug in your industry and motor application details, and give a good estimate of energy, CO2 and cost savings, as well as payback period. They also price up the benefits for applications switching to VSDs in place of traditional DOL (direct-on-line) starting.
Those will invariably show that the savings from installing a drive to reduce motor speeds – especially on quadratic loads, such as pumps and fans – far outweigh anything likely to be achieved by stepping up the motor efficiency ladder. That's why the regulations are framed to allow IE2 motors with VSDs. As Glover puts it: "The legislators obviously understood that VSDs offer a powerful route to major energy savings. Moving up to IE3 then results in relatively marginal improvements." But, as stated, still worthwhile.
Nuisance tripping
However, coincidentally, VSDs (and soft starts) also solve a potential nuisance tripping problem where IE3 motors are concerned. That's because they eliminate the need for LV switchgear – and specifically circuit breakers – as used in DOL configurations. Mark Harrison, Siemens product manager for Sirius LV control gear, explains that, whereas inrush currents on IE2 motors are usually seven or eight times rated current, those for IE3 machines can be much higher.
"Our research on 3,000 IE3 motors of various sizes and from a range of manufacturers shows that the starting current can rise to 10 times," he says. That is due to the typically elongated rotor, greater material content, the recued air gap, etc. What's more, Siemens' study also suggests that many motors will see an inrush spike up to 20-times full load current for the first quarter cycle (20–40msec). So, given that circuit breakers are typically sized to release at 13-times rated load, there is a risk that DOL starters may trip.
Be warned. Siemens' solution for the vast majority that still use DOL motor starting has been to offer upgraded IE3-ready control gear, with beefed up contactors (using improved silver alloy tips) and, importantly, with tolerances tightened beyond the standard IEC 60947 requirements. Harrison explains that these enhancements, coupled with Siemens' decision to produce overlapping ranges, means that engineers can accurately size circuit breakers to handle the greater inrush spikes yet still maintain full motor protection.
What about the other key issues relating to moving up from IE2 to IE3 motors – particularly price implications, footprint variance, weight changes and any impacts on robustness and hence longevity? Clearly, setting aside Siemens' stance, price delta is going to vary according to manufacturer and motor size. However, IE3 motors are now essentially commodity items, so volumes are significant and competition fierce. That being the case, best estimates are a maximum 10–20% price hike – figures that are easily self financing from energy savings.
However, that's not always the case. "For most motors, manufacturers are able to offer IE3 power and speed rating in the same frame size as their IE2 counterparts," advises Glover. "But others will require a larger frame and better cooling, which in turn means more, and higher-grade active materials – laminations and copper – that are bound to cost more." And he adds that price increases are likely to be highest for the smaller motor ranges, if only due to the complexity of manufacture. "We're cramming more into a smaller enclosure."
Those observations answer the question about footprint: for the vast majority, frame sizes won't alter so, mechanically, retrofitting will be straightforward. Don't be surprised to see longer motors though (up to 10%). Many will show slightly deeper end shields to accommodate the extended rotor windings, but that still won't change the footprint or the shaft dimensions, all of which are standardised.
Nor will it alter the motor weight significantly: best estimates for a mid-range, four-pole motor rated for 1,480 rpm suggest approximately 1kg increase. And remember, the likelihood is that, because IE3 motors size-for-size run slightly cooler and with reduced mechanical stresses, key components, such as the bearings and insulation, should last longer.
IE4 motor efficiency package
Trade-offs between achieving energy reductions and improving motor control intelligence are a thing of the past with ABB's SynRM (synchronous reluctance) IE4 super-premium efficiency motor and variable speed drive (VSD) combination packs. That's the claim from the automation giant, which explains that SynRM combines all of the energy-saving benefits of permanent magnet technology together with the familiarity of an induction motor, paired with an ABB industrial VSD running the latest process control software.
ABB's motor has no conventional rotor windings, so runs cooler than traditional induction motors, with power losses typically 40% down. Two versions are available: one comprising a motor the same physical size as a standard IE3 induction motor but operating at IE4 efficiency; the other, dubbed High Output and typically two frame sizes smaller, but running at IE3.
Either way, the result is significantly better power density and higher energy efficiency, while lower temperatures mean longer bearing life and extended maintenance re-greasing intervals. Compared to permanent magnet motors, SynRM is also lighter, less expensive and easier to repair.
As for the VSD, that is required to control this motor type and is available in several variants. For example, the drive for water and wastewater (ACQ810) comes in 0.37–500kW power ratings, while the industrial drive (ACS880) is rated 0.55–2,800 kW. Each has functionality appropriate to the industry, with features such as: direct torque control (DTC), designed for high-precision motor torque and speed; and safe torque-off for isolation. There are also safety functions that comply with the Machinery Directive and programming tools for process control.