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Motors & Drives


4 For buyers of plant and machinery who appreciate that the cost of ownership is more significant than the purchase price, energy efficiency is a very important factor. Alistair Rae reports on the European Minimum Energy Performance Standard scheme for electric motors, and highlights some of the most efficient motors currently available.


Looking ahead to the next generation of energy- efficient motors


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ccording to the IEC (International Electrotechnical Commission), industry accounts for approximately 42 per cent of the world’s consumption of electricity, with


around two-thirds of this used by electric motors. Given the need to reduce energy consumption, designers are starting to consider motors that are even more efficient than the units built to comply with current legislation. The efficiency of an electric motor is defined


as the ratio of usable shaft power to electric input power. International standard IEC 60034-30, Rotating electrical machines - Part 30: Efficiency classes of single-speed, three-phase, cage-induction motors (IE-code), lists three motor efficiency classes: IE1 is the base standard, IE2 stands for high efficiency and IE3 for premium efficiency. The standard also mentions a future level above IE3 to be called IE4 super premium efficiency. Even though the standard does not yet provide the full technical specifications, a few manufacturers are introducing IE4 motors. As of 16 June 2011, only motors that meet or


exceed the IE2 level are permitted to be sold and installed in the EU. From January 2015 all motors will need to reach the IE3 level (or IE2 motors


can be used if they are controlled by variable- speed drives). The EU Meps (Minimum Energy Performance Standard) scheme, which mandates compliance with the IEC 60034-30 energy- efficiency classes, covers most two-, four- and six- pole motors rated from 0.75 to 375kW for power supplies at 50 and 60Hz. It is predicted that some 30 million existing


industrial motors in Europe alone will gradually be replaced under the Meps scheme, resulting in energy savings in the order of 5.5 billion kilowatt-hours of electricity each year and a corresponding reduction in carbon dioxide emissions of 3.4 million tonnes.


Motor designs


Before looking at IE4 motors, it is worth reviewing how IE2 and IE3 motors differ from IE1 motors. Dr Sebastião Lauro Nau is responsible for motor research and development at WEG. He explains that IE2 and IE3 motors use low-loss grades of steel for the laminations and more active material - such as steel laminations, copper and aluminium - to reduce the total losses. These lower losses increase energy efficiency and reduce the temperature rise in the motor, which also extends its operating life. Others performance characteristics remain the same as for IE1 motors.


Fig. 1. WEG WQuattro motors integrate a conventional three-phase distributed winding with a rotor featuring an aluminium cage and internal high-energy magnets.


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