Premium efficiency, when used in reference to specific types of Electric Motors (with a rotating shaft), is a class of motor efficiency. As part of a concerted effort worldwide to reduce energy consumption, CO2 emissions and the impact of industrial operations on the environment, various regulatory authorities in many countries have introduced, or are planning, legislation to encourage the manufacture and use of higher efficiency electrically powered motors. This article looks at the development of the premium efficiency standard (IE3) and premium efficiency motors (PEMs) and associated environmental, legal and energy-related topics.
History The oil crisis and the worldwide need for more power, more electrical power, and consequently more power stations have raised energy conservation awareness. In 1992 the U.S. Congress, as part of the Energy Policy Act (EPAct) set minimum efficiency levels (see Table B-1) for electric motors.
In 1998 the European Committee of Manufacturers of Electrical Machines and Power systems (CEMEP) issued a voluntary agreement of motor manufacturers on efficiency classification, with three efficiency classes:
Eff 1 for High Efficiency Eff 2 for Standard Efficiency Eff 3 for Low Efficiency
Premium efficiency electrical motors The term premium efficiency as discussed here relates to a class of motor efficiency. It is thought necessary to introduce this term associated with motors because of forthcoming legislation in the EU, USA and other countries regarding the future mandatory use of premium-efficiency squirrel cage induction type motors in defined equipment.
Reducing energy consumption and CO2 emissions Several statements have been made regarding motor use and the advantages of using premium-efficiency or higher efficiency motors. These include: Based on U.S. Department of Energy data, it is estimated that the National Electrical Manufacturers Association (NEMA) premium-efficiency motor program would save 5.8 terawatts of electricity and prevent the release of nearly 80 million metric tons of carbon into the atmosphere over the next ten years. This is equivalent to keeping 16 million cars off the road. Roughly 30 million new electric motors are sold each year for industrial purposes. Some 300 million motors are in use in industry, infrastructure and large buildings. These electric motors are responsible for 40% of global electricity used to drive pumps, fans, compressors and other mechanical traction equipment. Motor technology has evolved over the last few decades. Superior so-called "premium" products are now available, ready to change the market toward energy efficiency and to contribute in lowering greenhouse gas emissions worldwide. With using best practice energy efficiency of electrical motors can be improved by 20% to 30% on average. Most improvements have a pay back time of 1 to 3 years. This can result in a potential impact on reduction of global greenhouse gas emissions. Electric motor systems consume large amounts of electrical energy and can provide an opportunity for significant energy savings. Energy represents more than 97 percent of total motor operating costs over the motor's lifetime. However, the purchase of a new motor often tends to be driven by the price, not the electricity it will consume. Even a small improvement in efficiency could result in significant energy and cost savings. Investing a little more money upfront for a more efficient motor is often paid back in energy savings. Improving energy efficiency reduces greenhouse gas emissions that contribute to climate change.
Definition of motor efficiency The efficiency of an electric motor is represented by the Greek letter Eta and defined as the ratio of output mechanical power to electric input power and can be calculated using this formula:
η = O u t p u t M e c h a n i c a l P o w e r I n p u t E l e c t r i c a l P o w e r {\displaystyle \eta ={\frac {OutputMechanicalPower}{InputElectricalPower}}}
Since the efficiency is a ratio, as long as the unit of measure is the same for both the output and input power, any unit of measure can be used for this calculation. The shaft power is transferred to the machine driven; the electric input power is what is metered and charged for. Loss in motor efficiency is determined by the difference between the input power and output or shaft power. Ploss = Pin - Pshaft Ploss = losses of electric motor [kW] Motor energy loss is mainly heat caused by many factors, including loss from the coil winding (resistance), loss in the rotor bars and slip rings, loss due to magnetising of the iron core, and loss from friction of bearings.
Premium efficiency motor programs in USA On December 19, 2007, President Bush signed the Energy Independence and Security Act of 2007 (EISA) into law (Public Law 140-110). The National Electrical Manufacturers Association (NEMA) actively participated in crafting major provisions on EISA. A critical provision that NEMA focused on was increased motor efficiency levels. The Motor Generator section of NEMA joined forces with the American Council for an Energy Efficient Economy to draft and recommend new motor efficiency regulations covering both general purpose and some categories of definite and special purpose electrical motors. The Motor and Generator Section of NEMA established the NEMA Premium program for four main reasons:
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