Premium efficiency refers to a type of motor efficiency found in certain electric motors that have a rotating shaft.
To help reduce energy use, carbon dioxide emissions, and harm to the environment caused by industrial activities, government agencies in many countries have created or are planning laws to support the making and use of electric motors with higher efficiency. This article discusses the development of the premium efficiency standard, known as IE3, and premium efficiency motors (PEMs), along with topics related to the environment, laws, and energy.
History
The energy shortage and the global demand for more electricity, which requires more power plants, have made people more aware of the need to save energy.
In 1992, the U.S. Congress, as part of a law called the Energy Policy Act (EPAct), required electric motors to meet certain efficiency standards (see Table B-1).
In 1998, the European Committee of Makers of Electrical Machines and Power Systems (CEMEP) agreed to set standards for motor efficiency. These standards included 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" refers to a type of motor efficiency. This term is important to discuss because new laws in the EU, USA, and other countries will require the use of premium-efficiency squirrel cage induction motors in certain equipment.
Reducing energy consumption and CO2emissions
Several statements have been made about using motors and the benefits of using premium-efficiency or higher efficiency motors. These include:
According to data from the U.S. Department of Energy, the National Electrical Manufacturers Association (NEMA) premium-efficiency motor program is expected to 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 amount of carbon saved is equal to keeping 16 million cars off the road.
Approximately 30 million new electric motors are sold each year for industrial use. Around 300 million motors are currently in use in industries, infrastructure, and large buildings. These motors are responsible for 40% of the world’s electricity used to power pumps, fans, compressors, and other mechanical equipment. Motor technology has improved over the past few decades, and better "premium" motors are now available. These motors can help the market move toward greater energy efficiency and reduce greenhouse gas emissions worldwide.
Using best practice energy efficiency methods can improve motor performance by 20% to 30% on average. Most improvements have a payback time of 1 to 3 years. This means there is a large potential for reducing global greenhouse gas emissions.
Electric motor systems use a lot of electrical energy and offer chances for significant energy savings. Energy costs make up more than 97% of total motor operating costs over the motor’s lifetime. However, the purchase of a new motor is often based on price rather than the electricity it will use. Even a small increase in efficiency can lead to major energy and cost savings. Spending a bit more money upfront for a more efficient motor is often repaid through energy savings. Improving energy efficiency helps reduce greenhouse gas emissions that contribute to climate change.
Definition of motor efficiency
The efficiency of an electric motor is shown using the Greek letter Eta (η) and is calculated by dividing the output mechanical power by the input electrical power. This can be written with the formula:
η = Output Mechanical Power / Input Electrical Power
Since efficiency is a ratio, the same unit of measurement can be used for both the output and input power, as long as they are consistent.
The shaft power is sent to the machine being driven, and the electric input power is measured and used for billing. The loss in motor efficiency is found by subtracting the output or shaft power from the input power.
Loss = losses of the electric motor [kW]
Motor energy loss is mainly heat caused by several factors, including loss from the coil winding due to resistance, loss in the rotor bars and slip rings, loss from magnetizing the iron core, and loss from friction in the 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) helped create important parts of EISA. A key part NEMA focused on was raising motor efficiency standards. The Motor and Generator section of NEMA worked with the American Council for an Energy Efficient Economy to write and suggest new motor efficiency rules for general purpose and some definite and special purpose electrical motors.
The Motor and Generator Section of NEMA started the NEMA Premium program for four reasons:
- Electric motors greatly affect the total energy costs for industrial, institutional, and commercial buildings.
- Electric motors have different levels of energy efficiency. The NEMA Premium program helps buyers find more efficient motors that save money and improve system reliability.
- NEMA Premium labeled motors help users improve motor system efficiency as changes occur in how utilities operate.
- NEMA Premium motors and improved systems use less electricity, which reduces pollution from power generation.
Visit NEMA Premium Motors for more information.
A summary of EISA standards for motors:
EU approach to premium efficiency motors
In June 2005, the European Union passed a Directive to create a system for setting eco-design rules, such as energy efficiency standards, for all energy-using products in residential, tertiary, and industrial areas. Consistent rules across the EU will help prevent differences in national laws from blocking trade between EU countries. The Directive does not set specific rules for individual products but outlines conditions and standards for setting requirements related to environmentally important product features, such as energy use. These standards can be updated quickly and efficiently. Specific steps will be taken later to establish the eco-design rules. In general, the Directive applies to all energy-using products except transport vehicles and includes all types of energy sources.
Unifying worldwide efficiency classifications
IEC 60034-30 sets electrical efficiency standards for single-speed, three-phase motors that operate at 50 Hz or 60 Hz. These motors must meet the following criteria:
- Have 2, 4, or 6 poles, which operate at 3,000, 1,500, or 1,000 RPM when used with 50 Hz power
- Produce between 0.75 and 375 kilowatts of power
- Operate at voltages up to 1,000 volts
- Are designed for continuous use or for use with a duty cycle that is 80% or more
The table below lists the IEC 60034-30 (2008) efficiency classes and similar efficiency levels.
The standard sets aside an IE4 class (Super Premium Efficiency) for future use. The following motors are not included in the new efficiency standard:
- Motors made only for use with inverters
- Motors that are fully integrated into machines like pumps, fans, or compressors and cannot be tested separately from the machine.
The graph shows an example of 50 Hz, 4-pole motors.
For 60 Hz operation, the IE2 and IE3 minimum full-load efficiency values are similar to the North American NEMA Energy Efficient and Premium Efficiency motor standards, respectively. NEMA specifies different full-load efficiency values for motors with Totally Enclosed Fan-Cooled and Open Drip-proof enclosures. Starting at 200 horsepower, 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 occurs because motor torque remains constant, so losses from resistance are the same at both frequencies. However, motor output power increases with speed, rising by 20% when frequency increases from 50 Hz to 60 Hz. Generally, 60 Hz efficiency is about 2.5% to 0.5% greater than 50 Hz efficiency. This difference is larger for smaller motor power ratings.
To meet these standards, motors must be tested using the new IEC 60034-2–1 testing method. This method produces results compatible with North American IEEE 112B and CSA 390 test methods. The new standard requires that the motor’s efficiency class and nominal efficiency be labeled on the motor nameplate and included in product literature and motor catalogs in the following format:
New minimum energy performance standards in EU
On July 22, 2009, Commission Regulation (EC) No. 640/2009, based on Directive 2005/32/EC, stated that in the European Union, motors must not be less efficient than the IE3 efficiency level starting January 1, 2015, except for some special uses.
- IE2 efficiency was required by June 16, 2011.
- IE3 efficiency was required by January 1, 2015, for motors ranging from 7.5 to 375 kW. IE2 efficiency was allowed only when used with an adjustable-speed drive.
- By January 1, 2017, all motors from 0.75 to 375 kW must meet IE3 efficiency. IE2 efficiency was allowed only when used with an adjustable-speed drive.
EC 60034–30 defines IE3 Premium Efficiency (%), which is shown in the table.
IE3 Premium Efficiency
Design of premium efficiency motors
Designing premium efficiency motors requires special knowledge, experience, and testing equipment with advanced tools. The goal of the design is to increase efficiency by reducing and balancing different types of energy loss, especially those in the stator coils, the stator iron (magnetizing), and the rotor losses caused by slip. Compared to standard motors (such as IE1), premium efficiency motors (like IE3) use more iron and copper materials. These motors are heavier and larger in size than IE1 motors.
Typically, using more copper in the windings, thinner steel layers with better properties, smaller gaps between parts, improved cooling fans, and stronger bearings can help increase motor efficiency. Copper conducts electricity better than other metals, which improves motor efficiency. Using thicker wires and more material in the coils also increases efficiency. When energy savings are a main goal, induction motors can be designed to meet or exceed National Electrical Manufacturers Association (NEMA) premium efficiency standards.
Commercial rebate programs
The U.S. Senate Energy and Natural Resources Committee approved a plan suggested by NEMA, which created a program that gives money back for buying energy-efficient motors. This program, called the "Crush for Credit" program, provided $25 for each horsepower of a new motor and $5 for each horsepower of an old motor that was removed. The second part of the program helped cover the cost difference between newer, more expensive efficient motors and older, less expensive but less efficient motors. This program allowed the federal government to spend $350 million to encourage the use of NEMA Premium motors.
The "Crush for Credit" plan, included in the Senate's version of the Energy Policy and Conservation Act (EPCA), lasted for five years. It included the following funding amounts:
• $80,000,000 in Fiscal Year 2010
• $75,000,000 in Fiscal Year 2011
• $70,000,000 in Fiscal Year 2012
• $65,000,000 in Fiscal Year 2013
• $60,000,000 in Fiscal Year 2014
In the European Union, several Capital Allowance Schemes help companies buy equipment that includes premium-efficiency motors. For example, in the United Kingdom, the Enhanced Capital Allowances (ECA) Scheme gives tax benefits to businesses that invest in equipment that meets energy-saving standards. The Energy Technology List (ETL) explains the requirements for each type of technology and lists products that meet these standards. The ETL is managed by the Carbon Trust on behalf of the government and has two parts:
- The Energy Technology Criteria List (ETCL), which is reviewed each year to ensure it reflects new technology. It sets the energy-saving requirements for each type of equipment.
- The Energy Technology Product List (ETPL), which is updated monthly on a website. It lists products and technologies that qualify for ECAs.
The ETPL also includes information about the maximum tax benefits companies can claim for products that are part of larger machines or systems that do not themselves qualify for ECAs.
Key features of the ECA scheme include:
• Available to all UK businesses that pay corporation or income tax, regardless of size, industry, or location.
• Provides 100% tax benefits in the first year for buying energy-saving equipment.
• All products listed on the ETPL must meet energy-saving standards outlined in the ETCL.
• Only new and unused energy-saving equipment qualifies for ECAs.
• Tax benefits apply to the cost of buying and installing qualifying equipment, including some installation and transportation costs. More details can be found in the "Claiming an ECA" section.
In Ireland, a similar program called the Accelerated Capital Allowance (ACA), managed by Sustainable Energy Ireland (SEI), allows companies to reduce their taxable income by 100% of the cost of eligible energy-efficient equipment in the first year of purchase. This is compared to 12.5% for non-eligible equipment.
Under the current Capital Allowances tax system, companies can reduce their profits by the cost of "capital equipment" over eight years, meaning the tax reduction each year is 1/8 of the total cost.
With the new ACA program, companies can deduct the full cost of "Eligible energy-efficient capital equipment" from their profits in the year they purchase it, meaning the full cost is subtracted from their taxable profit in the first year.