Energy Independance & Security Act of 2007

The past twenty-plus years focused on the efficiency of “general-purpose” motors. Energy Policy Act (EPAct) of 1992 covered only AC induction motors of 1 – 200 horsepower with rigid mounting bases. The Energy Independence and Security Act of 2007 builds on this legislation and expands coverage through 500 HP. However NEMA energy efficient and Premium® motors are available with many additional mounting configurations and enclosures. Use of Premium Efficient motors can save significant energy – all the more important in today’s higher energy price market. NEMA Premium® defines the minimum efficiency of the motor, not the motor’s mounting configuration. In addition, 250 – 500 HP medium voltage motors are also defined by NEMA Premium® even thought they are excluded from either legislation.

Any motor upgrade should be evaluated by the motor’s life cycle cost, rather than just its purchase price. Figure 1 shows the life cycle cost of a typical AC induction motor consists of only 2 percent for the purchase price and over 97 percent for the energy used over its life.

Thus, looking beyond general-purpose motors can result in significant energy savings.

Low hanging fruit first

The Energy Independence and Security Act of 2007 (EISA) was passed by Congress and signed into law on December 19, 2007. EISA builds upon the previous EPAct (Energy Policy Act of 1992) updating mandated efficiency standards for general purpose, three-phase AC industrial motors from 1 to 500 horsepower which are manufactured for sale in the United States. The U.S. Department of Energy (DOE) is responsible for establishing the rules to implement and enforce EPAct. EISA applies to motors manufactured after December 19, 2010.

The efficiency standards under EISA for each general-purpose rating (Subtype I) from 1 to 200 horsepower that was previously covered by EPAct specifies a nominal full-load efficiency level based on NEMA Premium® efficiency as shown in NEMA MG 1, Table 12-12. All such motors currently under EPAct, manufactured after December 19, 2010, must meet or exceed this efficiency level.

General Purpose Electric Motors (Subtype II) not previously covered by EPAct will be required to comply with Energy Efficient efficiencies as defined by NEMA MG 1, Table 12-11. The term `general purpose electric motor (subtype II)’ means motors incorporating the design elements of a general purpose electric motor (subtype I) that are configured as 1 of the following:
• U-Frame Motor.
• Design C Motor.
• Close-coupled pump motor.
• C-face or D-flange footless motor.
• Vertical solid shaft normal thrust motor (as tested in a horizontal configuration).
• An 8-pole motor (900 rpm).
• A poly-phase motor with voltage of not more than 600 volts (other than 230 or 460 volts.
• 201 – 500 horsepower motors not previously covered by EPAct will be required to comply with Energy Efficient efficiencies as defined by NEMA MG 1, Table 12-11.

Fractional HP and 48 or 56 frame motors are not included in EISA. Only 1 – 500 HP motors with 3-digit frame NEMA numbers (143T-up) included in EISA. This also includes equivalent IEC frame designations.

Generally, the mandated efficiency levels of EISA for Subtype I motors fall at the present efficiencies of existing NEMA Premium® efficient motors for general-purpose 1 – 200 HP motors, such as Baldor’s Super-E®.

The Subtype II 1 – 200 HP and general purpose 201 – 500 HP motors may require manufacturers to raise efficiency of some designs to comply with MG 1, Table 12-11, however many designs may already comply. NEMA Premium® efficient motors will meet or exceed the EISA requirements for either of these motor types.

Several motor configurations are not covered by EISA such as:
• Single phase motors
• DC motors
• Design D with high slip
• Adjustable speed with optimized windings
• Customized OEM mounting
• Intermittent duty
• Integral with gearing or brake where motor cannot be used separately
• Submersible motors

Not every three-phase electric motor from 1 to 500 horsepower configuration falls under EISA, but almost all motors except some special OEM designs with proprietary mounting configurations do. The following motor configurations are exempt from EISA compliance:
• Integral gearmotors
• Integral brake motors
• Inverter duty motors with windings optimized for ASD use that cannot be line-started
• Design D high-slip motors

EISA requires that any custom motors included in OEM equipment that fall within the guidelines of the act will comply with the efficiency levels for that type of motor. Each OEM should prepare for the changes well before December of 2010 and develop designs immediately, particularly when UL or CSA approvals are required.

EISA makes no distinction for duty cycle rating. Again, one has to look at the EPAct definition of “electric motors” and “general purpose” to determine if a particular design falls under the requirements.

The DOE considers motors built to IEC metric frame dimensions equivalent to NEMA T-frame dimension to fall under EISA.

EISA also makes no distinction between stock or custom motors. The determining factor under EISA is whether a particular motor meets the law’s definition of “electric motor”.
EISA also applies to motors manufactured outside of the United States and imported for use. This also includes the electric motors “as a component of another piece of equipment”.

EISA does not apply to motors exported outside the United States, including motors mounted on equipment. The DOE will require these motors or their boxes to be specifically marked “Intended for Export”. Countries outside of the United States are enacting their own Minimum Efficiency Performance Requirements (MEPS) that may require compliance.

EISA does not contain any requirement to replace electric motors in use. Nor does the law affect the repair of older motors already in service.

EISA does not affect any inventories of electric motors. The law only applies to new motors manufactured after December 19, 2010. Motors in inventory on that date can be sold or used as before the law.
Step up to NEMA Premium® motors

More energy savings could be obtained by use of the higher efficiency NEMA Premium® motors as defined in tables 12-12 and 12-13 of NEMA MG-1. NEMA Premium® efficient motors are rated at 1 through 500 HP in low and medium voltage with Design A and B characteristics. These higher efficiencies are used in most North American rebate programs, Federal Energy Management Program (FEMP) and the Energy Policy Act of 2005. Approximately 22 - 25 percent of motors sold in North America now have these premium efficiencies and use of these motors is growing at a higher rate than EPAct motors.

NEMA does not designate the mechanical configuration for NEMA Premium® motors. Manufacturers are supplying them in all usual configurations and enclosures including C-face and vertical pump mount, explosion proof, washdown duty, IEEE 841, etc. Most any application requiring a Design B motor may be supplied with premium efficiency.

Additional benefits beyond reduced electrical use generally include features that provide for longer life and reduced downtime in the application. Lower temperature rise and better balance results in longer grease and bearing life. Cast iron frames with machined mounting bases provide easier alignment and help to reduce noise and vibration. When upgrading the motor, there is also an opportunity to improve the environmental protection of the motor to reduce bearing and winding failures. Many users will argue that savings from reduced downtime is worth much more than energy savings alone.

Rebates and incentives for premium motors are available in many states and all Canadian Provinces. The states having the lowest costs for electricity generally do not have programs to encourage industry to switch to premium motors. Calculations result in paybacks of over two years resulting in decisions to replace on failure. A U.S. Department of Energy report estimated that it would take 18 years to replace all motors on failure. Incentives, tax credits and accelerated depreciation would help industry quickly upgrade to premium motors.


System review for maximum savings

Although electric savings from upgrading to premium motors is significant, analysis of the system generally provides much more savings. The DOE report states that adding and adjustable speed drive to a pump or fan could reduce consumption by 30-50 percent. Payback on adding an inverter for an application like this could be in as little as 6 months without incentives. Generally such an upgrade would be done in conjunction with adding a premium motor. The robust insulation system of NEMA Premium® motors are suitable for use with the Pulse Width Modulated (PWM) waveform supplied by inverters.
If possible the system should be analyzed beyond simple motor replacement. Additional savings are possible by replacing V-belts with energy-efficient cogged belts that could raise system efficiency by up to 3 percent and have quick paybacks of less than 6 months.

If a right angle worm speed reducer is used, changing to an inline helical or right angle bevel reducer could raise the efficiency by 20 – 50 percent. This means that a lower horsepower motor could be used to drive the load resulting in a lower initial price and also less electricity consumed.

Consider upgrading DC motors

Many machines in industry such as plastic extruders continue to rely on DC motors for their main power. Extruders are powered by 40 – 400 HP motors that have efficiency in the 88 - 92 percent range. This is not low, but not as high as NEMA Premium® motors at 94 – 96 percent. The DC motors require an SCR (thyristor) adjustable speed control. Energy savings are possible when switching from a DC to AC motor and drive. Additional savings will be seen from eliminating the brush and commutator maintenance on all DC motors. Plus the newer AC vector controls can offer more accurate process control than older analog DC controls. A 40 HP DC motor with 88% efficiency requires $8,816 worth of electricity ($0.10/kWh) to operate 2-shifts. An AC motor would have 94.5% efficiency and require $8,210 to operate, a $606 per year savings. Additional savings are from elimination of brush and commutator maintenance and eliminating downtime from removing the machine from operation. It may take an hour for brush replacement and three hours to remove the motor and replace it with a spare so commutator service may be performed. At typical downtime of $10,000 per hour, savings from eliminating typical DC maintenance is significant.

Single-phase motor use

Many large capital machines are supplied with three-phase motors for operation. When specifying this equipment, the savvy purchaser would look at life cycle cost and select NEMA Premium® motors where justified. Some machinery may come with PM rotor servos. But some may be supplied with single-phase motors on auxiliary equipment such as a chip conveyor on a high-tech CNC machining center. This single-phase motor is very inefficient and should be replaced with a three-phase motor for electricity savings and to prevent downtime from potential failure of the starting switch or capacitor. Premium efficient motors are available for single phase, but they are not as efficient as general-purpose three-phase motors. Table 1 shows typical efficiency for single and three-phase motors.

Table 1. Comparison of Single vs. Three-phase Efficiencies
Motor Type Typical Efficiency
General-purpose single-phase motor 80.0%
Premium single-phase motor 86.5%
General-purpose three-phase motor 87.5%
NEMA Premium® three-phase motor 90.2%

Usually the worst three-phase motor has a higher efficiency than the best available single-phase motor. Always specify three-phase motors when possible.

Increased productivity and new technology

As energy surveys are completed, benchmarking of units produced per kWh should be established. Servomotors are being used to increase throughput by moving parts from place to place more quickly than a conventional fixed-speed conveyor. These high efficiency servos are replacing many air and hydraulic actuators. Servos also save in maintenance costs and production downtime.

Several manufacturers are producing higher output versions of these permanent magnet rotor motors through 500 HP or more. When compared to NEMA Premium® motors, the efficiencies by be up to 3 percent higher. An additional advantage is in the motor’s size and power density.

Much development has been done using die cast copper rotors instead of aluminum in AC induction motor construction. Although these copper rotors show efficiency improvements over use of aluminum, the author believes that other technologies such as permanent magnet rotors may show greater efficiency improvements. In addition, these PM rotor motors also greatly increase the power density available from a particular frame size. A conventional AC induction motor provides 5 HP from a 180 frame design and a PM rotor can provide 30 HP. Only 20 HP is possible from a conventional AC induction 250 frame motor but 100 HP is available from a PM rotor.

Table 2 compares efficiency available from various motor technologies.

Table 2. Comparison of motor efficiency
Motor Type – 30 HP – 4P Efficiency Annual Cost of Operation
Continuous operation Annual Savings
AC Induction – DOE Avg. 89.2 $21,979 -
AC Induction – EPAct 92.4 21,217 $762
AC Induction – NEMA Premium 94.1 20,834 1,145
AC Induction – Copper Rotor 94.5 20,746 1,233
Internal PM Rotor 94.9 20,658 1,321
Above based on $0.10 kWh

With continuing development of these PM-rotor motors, efficiencies of 98% or more are now possible for 400 – 500 HP motor designs. 4-pole TEFC versions of 250 - 500 HP AC induction motors would be 96.2% efficiency with standard versions in the 95.8% range. Although this doesn't seem like much difference, 3 shifts at $0.10 / kWh with a 400 HP, annual savings would be $1,134 and 11,340 kWh. These new permanent magnet designs are well above NEMA Premium® levels. Some large motors have tested to 98.3% efficiency. A 400 HP at 98.3% would save $5,805 a year over the 96.2% premium motor and $6,939 over the standard efficient motor.

Significant electric savings can be realized by using these permanent magnet motors and servomotors. Efficiency programs should recognize these PM rotor motors as an acceptable solution that would qualify for incentives and rebates.

Conclusion

All of these efforts require a market transformation to evaluating equipment and processes based on life cycle costs rather than first cost. As electric rates continue to increase, more industrial companies are beginning to seek solutions to help reduce their electricity costs. Existing technologies and “best practices” are available to reduce energy consumption by 30 – 50 percent according to the DOE. Many of these solutions are not covered by existing programs and may not even be suitable for custom programs, but need to be added. Adding these newer technologies to programs proposing additional federal tax incentives such as accelerated depreciation would help push along the transformation to more efficient equipment, resulting in less electricity used and less CO2 emissions.

In summary, the key points to remember are:
• Evaluate motor selection based on life cycle cost, not initial price.
• Specify NEMA Premium® efficient motors for continuous duty applications.
• Consider further upgrades to permanent magnet rotor motors for even greater efficiency.
• System efficiency upgrades are possible to maximize potential gains.
• Grooved high-efficiency V-belts.
• Replace DC motors with AC NEMA Premium® efficient motors.
• Consider use of high-efficiency helical or bevel gear reducers.
• Use pump or fan systems analysis tools.
• If possible, specify three-phase motors instead of single-phase motors.
• Newer technologies should be accepted into utility incentive programs.
• Government legislation may add additional tax incentives to reduce payback.

References
NEMA Standards Publication. MG-1 – 2006 Motors and Generators

U.S. Dept. Of Energy, United States Industrial Electric Motor Systems Market Opportunities Assessment, December 2002

M. Melfi, S. Rogers, S. Evon, B. Martin, Permanent Magnet Motors for Energy Savings in Industrial Applications, IEEE Petroleum and Chemical Industry Committee Conference, September 2006