AC Motor Efficiency - A Guide to Energy Savings
What we have done, and what we are doing
|
Introduction
|
Objectives
|
History
|
US Energy Policy Act
|
Part 1: OVERVIEW Recent attention focused on the energy savings potential of the electric motor has resulted in an industry–wide re-examination of motor design and the emergence of motor efficiency as a major user customer concern. Because of the general misunderstanding of the question of efficiency, many motors are being misapplied and users are not receiving what they are paying for, or are not taking advantage of energy savings that may well exist. This paper is intended to state the position of Reliance Industrial Company in regard to the use and application of premium efficient motors. Reliance believes this technology is vital to global competitiveness and must be understood and properly applied to maximize the benefit. In the late 1970’s the energy crisis reached a peak. Long gasoline lines and skyrocketing energy costs sent the world scrambling for legitimate energy savings means. The U.S. Government commissioned studies by the FEA (Federal Energy Administration) which later became the Department of Energy (D.O.E.). One study established that electric motors utilized almost 60% of all of the power generated in the U.S., and in industry, that number jumps to 80%. Some of the top industries are shown in Table 1:
Table 1 Reliance developed the first new generation premium efficient motor, the "XE" Extra Efficient, to meet industries demand for a motor which reduced energy consumption. In the years since the oil crisis, many industries who utilize motors running continuously in a process, such as petro/chemical and paper, have virtually standardized on premium efficient motors and continually seek even greater savings. However, when the gas lines disappeared the interests of some have, again, turned to first cost and less analysis of the savings even though electricity prices continue to rise. This attitude has allowed the energy efficient motor market to become clouded with a proliferation of non-premium products, such as standard efficient motors with stickers which state "High Efficiency" or "Energy Saving Motor" and products with efficiencies in between standard efficient and the best energy efficient product offered by that manufacturer. Recently, pressure is once again mounting to provide only the best product available and this pressure comes from many sources. Some sources you would expect, such as environmental groups and the government, and others you may not expect, such as educational campaigns by utilities and incentives such as rebates on energy efficient motors. When the utilities put up incentive money they will not settle for second best. Why are the utilities interested in energy efficiency when they sell power for a living? The answer is quite simple, saving energy may allow them to avoid or at least delay building new power generating facilities which are very expensive compared to conservation. And with concerns over the environment, the difficulty in bringing new capacity on line is increasing. Since the "XE" motors were introduced in the late 70’s, technology and manufacturing changes have allowed the efficiencies to continue to increase and ongoing development will continue to increase these efficiencies in the future. United States Energy Policy Act On October 24, 1992 President Bush signed into legislation the Energy Policy Act. This act known as "EPAC" established efficiency levels for electrical appliances and equipment including general purpose industrial electric motors. The law goes into effect on October 24, 1997 and defines specific efficiency levels, testing and labeling procedures. All electric motors covered by this Act must meet the nominal full load efficiency as defined by NEMA table 12-10 "Full-load efficiencies of energy efficient motors." The Act sets new standards for general purpose industrial electrical motor efficiency. This higher efficiency should result in a reduction in U.S. energy demand and greenhouse gas emissions. Today, the act covers electric motors characterized by the following:
Regulations surrounding this new law are currently being developed. It is likely that the Department of Energy will broaden the standards to include all standard motors with voltages below 600 volts and motors with mechanical modification or mounting configurations that have no effect on efficiency such as C-face and D-flange motors. Motors for hazardous duty application are specifically included and covered by this efficiency regulation. Motors that are excluded from the law include the following:
There are currently discussions on going as to what constitutes a special purpose and a definite purpose motor. NEMA has recommended that motors such as; brake motors, arbor saw motors, motors with unique customer specific end shields, sleeve bearing designs, thrust bearing designs and encapsulated winding designs be defined as special purpose. NEMA has additionally recommended that definite motors should include totally enclosed non-ventilated (TENV), totally enclosed air over (TEAO), and closed couple pumps designs. Motor designs must be tested in accordance with IEEE 112, method B, which includes a complete dynamometer test. All testing must be conducted using equipment and methods that meet U.S. Department of Energy and National Institute of Standard of Technology (NIST) standards. All motors which are covered by the Energy Policy Act must be labeled accordingly with the NEMA nominal efficiency on the motor nameplate in accordance with NEMA MG 1-12.59 standards. Rather than be characterized as consumers of electric power, it should be pointed out that electric motors convert electrical energy to mechanical energy to do useful work which would otherwise be done with manpower, animal power or other forms of energy. The only power actually consumed by motors is electrical energy, or watts, lost during the conversion process, which takes the form of heat dissipated by the motor’s frame.
Figure 1 graphically depicts a 90.5% efficient 50 HP motor coupled to a load, in this case a pump, requiring 50 HP or 37.3 KW of mechanical input power. The total electric input power is 41.2 KW of which 37.3 KW is converted to mechanical power required by the pump load. This motor actually "consumes" 3.9 KW of power in this conversion process. Overall, the DOE study addressed itself to many aspects of energy efficiency and electric motors - both from the point-of-view of the manufacturer and the end-user. The study served as the basis for a thorough industry re-examination of all aspects of efficiency, including motor design manufacture, efficiency testing and labeling. Reliance responded quickly to industries demands for energy efficient motor products by offering the XE product line - a complete line of premium energy efficient motor products. Reliance also was the first motor manufacturer to offer E-Master - a cost effective full line of motors specifically designed to be in compliance with the Energy Policy Act. The use of these energy efficient products offers substantial reduction in motor watts losses and when applied properly, can reduce the industrial power consumption significantly. In most cases, the motor’s initial price premium can be totally justified in energy savings, and, in many cases using total life cycle costing considerations, the entire motor cost, not just the initial price premium, and be justified. Users of electric motors need education in the energy savings benefits and cost justification methods associated with the application of these energy efficient alternatives. Reliance hopes this paper will provide a basic guideline and better understanding of the potential savings associated with the proper application of the E-Master and XE energy efficient motor products. |
||||
| Copyright ©2007, Baldor Electric Company.
All Rights Reserved. |