Efficiency drive

Mandatory efficiency standards for industrial three-phase induction motors will be announced this month, when the European Parliament and Council accept draft regulations agreed in March by the Commission. The legislation will see requirements for higher efficiency two-, four- and six-pole electric motors being phased in from 16 June 2011 – although brake motors, machines used above 400oC and those under ATEX hazardous area rules in, for example, the process industries, are bound to be exempt. The changes are part of Europe's ongoing push to reduce carbon emissions under the EuP Directive: EcoDesign Requirements for Energy Using Products. They have been driven by the realisation that motors consume a staggering 65% of electricity at industrial sites – a fact made plain when you consider that each motor, on average, consumes its entire purchase price in energy within the first month of operation. The intention, according to the EC, is that by 2020, electricity savings across Europe will be equivalent to the entire annual energy consumption of Sweden. British industry alone is expected to save £200 million and at least 1 million tonnes of CO2 per year. So, like it or not, the writing is on the wall: within the next couple of years, all factories will have to buy higher efficiency electric motors, no doubt at premium prices. Or will they? In the first wave, all low-voltage motors for sale will have to conform at least to high efficiency class IE2 (equivalent to today's best Eff1 voluntary code), as defined under the harmonised IEC efficiency standard 60034-30, introduced last year. Phase two will follow in January 2015, when all new industrial motors in the 7.5 to 375kW range, purchased in the EU, will have to meet IE3 (premium efficiency) – unless used with an efficiency-enhancing variable speed drive (of which more later), in which case cheaper IE2 motors will still be allowed. Then finally, in 2017 phase three will require factory managers to buy IE3 efficiency rated motors right down to 0.75kW – almost certainly ushering in ultra high efficiency technologies, such as permanent magnet and switched reluctance. Is it going to cost British industry? Initially, probably yes: higher efficiency motors are currently more expensive. However, as ABB general manager of drives and motors Steve Ruddell says, there are also incontrovertible benefits, not only in terms of cheaper running costs (generally estimated at between 1.5% and 7%, depending on kW rating), but also reduced maintenance, due, for example, to the fact that higher efficiency motors run at lower temperatures, which translates into longer bearing and winding life. What's more, there are any number of applications where high efficiency motors can change the game: for example, operating as direct-drive units, so eliminating the capital and installation costs of conventional induction motor and gearbox combinations. It's also the case that permanent magnet (synchronous) motors offer better control at slower speeds and don't need speed feedback – meaning opportunities for higher accuracy and more resilient operation in some applications. Indeed, there is an argument that high efficiency – rather than cheapest – motors should have been the default choice for many years, even on general duties. Either way, Ruddell actually believes the new legislation is too little, too late: "We should have had this earlier. It's such a shame that we're now having to legislate after China, India and the US," he says. And he adds that ABB is aghast at some of the exclusions. "We believe the legislators have missed a trick. Hazardous area Ex d [flameproof] and n [non incendive] electric motors, for example, should have been included. They're used 24/7 in the oil and gas, chemical and pharmaceutical sectors, so they're very big electricity consumers." He also questions the EC's decision to limit its second phase to 375kW motors, commenting that high efficiency LV machines have been available for duties up to 1MW for some time – and that older motors in this range are big polluters. And he has one other major concern: "This legislation is not going to be retrospective, so what happens when existing electric motors fail? Will the EC allow motor rewinds to the old standards – which will be less efficient than as-new anyway? If so, since we estimate there are 11 million industrial LV motors out there, rewinds will hugely slow down the process of CO2 reduction. We believe that motors coming to the end of their life should be scrapped." Setting aside vested interest, these are valid points, largely echoed by Ian Ritchie, managing director of maintenance, repair and overhaul components manufacturer Brammer, who argues that there is no reason to wait until 2011 to examine your motor usage – or, for that matter, the benefits of using variable speed drives. "With help available from the Enhanced Capital Allowance Scheme and interest-free energy efficiency loans through the Carbon Trust, investing now in this area will have an immediate positive impact, in terms of reducing energy use and emissions, and enhancing production efficiency and competitiveness," he insists. Abbey Corrugated, which manufactures specialist board for a range of industry sectors, is one firm already convinced of the benefits of IE2 high efficiency motors. With energy one of its biggest costs and hundreds of electric motors at its Blunham, Bedfordshire site, the company is now only specifying IE2 products when it replaces motors. Process improvement manager Paul Gale says his calculations suggest between £1,000 and £10,000 savings per motor over a 10-year lifecycle, depending on the size of the motor. "As one of just 12 pathfinder companies for the new Carbon Trust standard on energy efficiency, we are committed to taking whatever steps are necessary to reduce energy consumption," says Gale. "It's clear that IE2 motors are the way to go, particularly in light of the new legislation." And with up to 20 motors being replaced at Blunham each year, he predicts significant savings over the next decade. But it's not just about motors. Just as important are the variable speed drives (VSDs) – and not just for phase 2 of the new legislation. Why? Because, although they too consume energy, it's peanuts compared to the 30%-40% (sometimes far more) they typically save on pump, fan and conveyor applications. Also, drives themselves have witnessed huge improvements in recent years – making installation and commissioning far simpler, while often improving operational flexibility. Also, many VSDs now have built-in PID controllers to cope even with quite advanced pump and fan automation, without buying or installing separate controls. As for the difference drives can make, look no further than these three: Plymouth-based semiconductor manufacturer X-Fab UK, API in Stockport and Romiley Board Mill in Manchester – each with very different applications, but all making the case for VSDs crystal clear. X-Fab, for example, reckons it has been saving £31,400 per year since installing ABB HVAC drives to run six 37kW fan motors on three cooling towers. And that's not including reduced maintenance costs in terms of replacing broken drive belts. Originally, the fans were star/delta connected and arranged in cascade format, switching to follow demand. According to Ted Judge, X-Fab's senior facilities engineer, that resulted in the final fan turning on and off, sometimes every 10 minutes, and drawing significant start-up current. Now, however, two fans start on the first towers at 20Hz; then as more cooling is required, the building management system brings in the next two and finally the remaining two. For further cooling, all six fans can run together under VSD speed control between 20 and 50Hz. Judge claims that the £15,000 installation provided payback in only six months. "I hadn't used drives much before Drive Control [the local ABB HVAC company] came along to give me a demonstration. I now see that using VSDs is the most effective way for us to save energy. I have a 10-year plan for how to reduce energy at this site and it will mainly be achieved with drives. 70% of electricity here at the plant is used by motors so there is vast potential." Meanwhile, engineers at a newly refurbished web laminating line in Stockport, operated by API, say they have doubled productivity and cut energy costs by 45%, following installation of their VSDs. Blackburn-based Optima Control Solutions developed the new system, completing its installation and commissioning of Parker Hannifin AC890 drives in just three weeks. Optima managing director Michael Hill explains that, originally, the laminator used a mechanical system with machine shafts or rollers being driven from PIV (positively infinitely variable) gearboxes, powered by dc motors with belts and pulleys. It was unreliable, difficult to maintain, expensive to run, and made product changeover a lengthy process that generated considerable scrap, since each PIV had to be manually adjusted. Also, the system provided poor control over web tension – meaning it couldn't be used on the lighter and more specialised films and foils now mostly now used by API. Optima replaced the common mechanical drive system with a series of drives, each controlling its own roller section with discrete control loops. Now, 13 closed-loop ac vector motors, each under VSD control and with a common dc bus, provide efficient power management – with energy naturally balanced between units under load and those that are regenerating when braking. Says Hill: "The drives have helped us make considerable improvements to machine functionality, to reduce set-up times and make it easier to operate. For example, as standard the drives [have] tension control, and the ability to control line speed set-points and set speed ratios between drives. They also have onboard I/O, which we used for speed set-points or load cell signals." He adds that the new system has made product changeovers quick and simple, using recipes stored in a new touchscreen HMI. Operators can now control individual web tensions for each section of the machine, he says – also enabling API to run a much wider range of materials through the refurbished line. It's a similar story at Romiley Board Mill, which manufactures paperboard from recycled fibre. Technical manager Ernie Domville says the firm increased paper output by 10%, with the help of ABB machinery drives on three electrically-driven machine sections, which are now synchronised with the rest of the paper machine, in turn driven by a line shaft. He explains that the firm wanted to increase output by adding a new dryer section to its paper machine. However, to avoid costly mechanical modifications to the line shaft, the new section needed to be electrically driven, while the new configuration of the machine also required independent speed control for its existing calendar and reel-up sections, using sectional drives. Making that work with modern, intelligent drives turned out not to be particularly difficult. In operation, the first drive now receives feedback from an encoder on the line shaft, and this set point is then cascaded from one drive to the next. Each drive then controls the speed of a 37kW ABB high efficiency ac motor in sync with the overall machine line shaft. In a conventional set-up, a PLC would have managed each of the three sections independently, each driven by a dc drive. But with the control capabilities of these drives, that wasn't necessary. "All functions for sectional speed control and communications are within each drive, which means that a controlling PLC is not required," confirm Domville. All convincing stuff. However, one final thought: if you're in any way concerned about a possible hidden environmental cost in terms of production of the drives themselves, consider this statistic, from ABB's Steve Ruddell. "The eco payback of a drive, compared with the emissions from manufacturing it, is just one day of operation."