July/August 2019

48 n MOTORS July/August 2019 www.drivesncontrols.com How can motors achieve ‘IE5’ efficiencies when there’s no standard? O ver the past few decades, electric motor-makers have enhanced their designs so that efficiency has improved significantly. This has been driven by the introduction of the IE standards for motor efficiency – the most recent being the IE4 classification which came into force in 2011. At that point, it was inevitable that the idea of an even higher standard, IE5, would be mooted. So far there is no official IE5 specification, but there are draft consultation proposals that basically call for a 20% improvement over IE4 motors. Several manufacturers have used these to develop their next generation of high-efficiency motors and are promoting them as being “IE5-ready”. As well as bringing ecological benefits, higher efficiency motors are also cheaper to run (if not purchase – more on that later), so they offer an immediate bottom-line benefit to users. This is particularly important for motors that run continuously or for long periods, while – naturally – bigger motors generate bigger savings. There are several possible approaches for improving motor efficiency, including the use of rare-earth magnets and reluctance motor technologies. However, most of these are expensive or have other drawbacks, such as complexity of design. The technology that is currently leading the way in efficiency improvements from a price and practicality point-of-view is the permanent magnet (PM) motor. These are similar to traditional induction motors, but they use permanent magnets rather than windings in their rotors. They generate a constant motor flux and thus improve full- load efficiency. Furthermore, the rotor is smaller and lighter, which leads to a smaller motor size, which can have benefits in terms of mounting and access for maintenance. The lighter rotor is also more precisely controllable, which explains why PM rotors are used in high-precision servomotors. Unlike induction motors, PM motors can only operate in conjunction with a variable-speed drive or inverter. However, this is not a disadvantage because the inverter allows adjustment of the shaft speed, so that it can be matched to the requirements of the application – and slower speeds result in significant energy savings. Drives are also commonly used on conventional motors to achieve improved control and energy efficiency, so the difference can be marginal on this point. Two key reasons are often cited for not installing high-efficiency motors: they tend to be more expensive to buy; and there are extra costs incurred during installation. However, the price premium is reducing and will continue to drop as PM motors become more common. Also, if installation is done in conjunction with a scheduled service or shutdown, costs are minimised. High-efficiency motors’ greatest ecological and economic gains will be achieved in applications with high duty cycles and where speed control can be controlled automatically to match demand – such as process pumps and ventilation fan drives, and conveyors in busy manufacturing plants and distribution centres. In short, motor manufacturers who follow the IE5-ready route are pre-empting standards that will certainly become legal requirements in the foreseeable future. And these “IE5” efficiency motors could help to achieve the UK government’s bold climate- stabilising target of net-zero carbon emissions by 2050. n Although no specification has been agreed yet for what constitutes an IE5 efficiency motor, several motor manufacturers are already offering machines that, they assert, meet IE5 requirements. David Ede, business development manager at TEC Electric Motors, explains what’s going on. TEC Electric Motors is one of several motor suppliers that are offering“IE5”motors even though no formal standard has been agreed for this efficiency class

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