As part of a concerted effort to reduce energy consumption, CO 2 emissions and the impact of industrial operations on the environment, This article looks at the development of the standard efficiency (IE3) and premium efficiency motors (PEMs) and associated environmental, legal and energy-related topics.
The oil crisis and the worldwide need for more energy. In 1992 the US 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:
The term “Premium efficiency” as discussed here relates to a class of motor efficiency. It is thought to be of importance in the EU, USA and other countries regarding the future mandatory use of premium-efficiency squirrel cage induction type motors in defined equipment.
Several statements have been made concerning motor use and the advantages of using premium-efficiency or higher efficiency motors. These include: Based on US 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 the world’s total power used to drive motors, fans, compressors and other mechanical traction equipment. Motor technology has been developed over the last few decades. Superior so-called “premium” products are now available, ready to change the market to energy efficiency and to contribute to lowering greenhouse gas emissions worldwide. Energy efficiency can be improved by 20% to 30% on average. Most recent developments have a pay back time of 1 to 3 years. This in addition means a big potential impact on global greenhouse gas emissions. Electric motor systems consumes 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 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.
The efficiency of an electric motor is defined as the ratio of usable shaft power to electric input power. η word = P shaft ÷ P in η word = motor efficiency [%] P shaft = shaft Power [kW] (in USA HP with factor 1.34) P in = electrical input from power supply [kW] The shaft power is transferred to the driven machine; the electric input power is what is metered and charged for. Loss in motor efficiency is determined by the difference between the power input and output or shaft power. P loss = P in – P shaft P loss = losses of electric motor [kW] Energy loss is caused by many factors, including loss of winding (resistance), loss in the rotor bars and slip rings, loss due to magnetising the iron core, and the loss of friction of bearings.
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) is actively involved in crafting major supplies on EISA. A critical provision that NEMA focused on 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 the use of electric motors. The Motor and Generator Section of NEMA has established the NEMA Premium program for four main reasons:
In June, 2005, the European Union enacted a guideline on establishing a framework for setting-up requirements for energy efficiency in the residential, tertiary and industrial sectors. Coherent EU-wide rules for eco-design will ensure that disparities among national regulations do not become obstacles to intra-EU trade. The guideline does not require direct reference, but rather defines the terms and conditions of the product, and allows them to be improved quickly and efficiently. It will be necessary to establish the eco-design requirements. In principle,
IEC 60034-30 specifies electrical efficiency classes for single-speed, three-phase, 50 Hz and 60 Hz, cage-induction motors that: The standard also reserves an IE4 class (Super Premium Efficiency) for the future. 50 Hz, 4-pole motors For 60 Hz operation, the IE2 and IE3 minimum full-load efficiency values are virtually identical to the North American National Electrical Manufacturers Association. NEMA) Energy Efficient and Premium Efficiency Motor Standards, respectively. (NEMA does not include full-load efficiency values for motors with Totally Enclosed Fan-Cooled and Open Drip-proof Enclosures and from 200HP IEC IE3 efficiency is slightly higher than NEMA Premium Efficiency). The IEC minimum full-load efficiency standards are higher for 60 Hz motors than for 50 Hz motors. This is because the motor torque is constant, I 2 R or winding resistance losses are the same at 50 Hz and 60 Hz. The motor output power, however, increases linearly with speed, increasing by 20% when the frequency is increased from 50 Hz to 60 Hz. In general, the 60 Hz efficiency is about 2.5% to 0.5% greater than the 50 Hz values. The efficiency gain is greater for smaller motor power ratings. To IEC 60034-2-1 testing protocol for testing compliance with these new efficiency standards. North American IEEE 112B and CSA 390 test methods.
On July 22, 2009, Commission Regulation (EC) No 640/2009 implementing Directive 2005/32 / EC states that in the EU, with the exception of some special applications, the motors will not be less efficient than the January 3 efficiency level 2015. In detail: IE3 Premium Efficiency
Design of Premium Efficiency Motors needs special knowledge, experience and test facilities, with precision instrumentation. The task of design is, to obtain the efficiency by minimizing and balancing the single losses, especially those created in the stator coils, the stator iron (magnetizing) and the losses within the rotor by slip. In comparison to standard (eg IE1) electrical motors, more iron and copper material are used. IE3 motors are heavier and smaller than IE1 motors. Typically use of higher slot fill in the copper winding, use of thinner laminations of improved steel properties, reducing the air gap, better design of cooling fan, use of special and improved bearings, etc. can ensure higher efficiency in the motors. The high electrical conductivity of copper versus other metallic conductors enhances the electrical energy efficiency of motors. Increasing the mass and cross section of conductors in a coil increases the electrical energy efficiency of the motor. Where energy savings are premium design objectives, Induction motors can be designed to meet and exceed National Electrical Manufacturers Association (NEMA) premium efficiency standards.
The US Senate Energy and Natural Resources Committee adopted a NEMA-advocated provision that created a premium energy-efficient motor rebate program, also known as a “crush for credit” program, according to the National Electrical Manufacturers Association (NEMA). The program provided a $ 25 per horsepower rebate and a $ 5 per horsepower rebate for the disposal of the old motor. NEMA says, “The last program is needed to cost the difference, more expensive, more efficient, and more inefficient motors. This program allowed the federal government to spend $ 350 million in incentives for the widespread adoption of NEMA Premium motors. The “Crush for Credit” contained in the Senate’s version of the “Energy Policy and Conservation Act” (EPCA) ran for five years, and including the following proposed funding: Key Features of the ECA scheme with capital allowances tax structure, where capital is available. ie the annual taxable profit is only reduced by 1/8 of the total equipment cost. With new ACA, when the money is spent on “Eligible energy efficient capital equipment”, the company can deduct the full cost of this equipment from its profits in the year of purchase, ie the taxable profit is reduced by the full cost of the equipment. “capital equipment” companies can deduct the cost of this equipment from their profits proportionally over a period of 8 years, ie the annual taxable profit is only reduced by 1/8 of the total equipment cost. With new ACA, when the money is spent on “Eligible energy efficient capital equipment”, the company can deduct the full cost of this equipment from its profits in the year of purchase, ie the taxable profit is reduced by the full cost of the equipment. “capital equipment” companies can deduct the cost of this equipment from their profits proportionally over a period of 8 years, ie the annual taxable profit is only reduced by 1/8 of the total equipment cost. With new ACA, when the money is spent on “Eligible energy efficient capital equipment”, the company can deduct the full cost of this equipment from its profits in the year of purchase, ie the taxable profit is reduced by the full cost of the equipment.
* NEMA website for the program