Motor decisions really do matter

by Wendy McTyre

Over its lifespan, what approximate percentage of a motor’s total costs accounts for its electricity costs?

The answer: An astounding 95 percent!

Industrial facility managers are usually surprised to learn that only about 5 percent of the lifetime cost of a motor is represented by other costs, including the purchase price, installation and repair costs.

Illustrated through this example, take a hypothetical 100 horsepower motor, 94.5 percent efficient (EPAct minimum for 1800 RPM, TEFC) with a list price of $8,000. Now assume that motor runs at full load for 6,300 hours per year with electricity costs at 7.5 cents per kWh. The annual electricity costs would be approximately $37,300, nearly five times the purchase price. Over that motor’s typical lifetime of 18 years, the electricity costs would be $671,400. By routinely specifying higher efficiency motors facility, managers can often reduce operating costs.

With the same motor provided in this example, consider that a 1 percent increase in efficiency would result in annual savings of approximately $352 per year. For a motor lasting 18 years, that is a savings of $6,336, or two-thirds the actual cost of the motor. Even greater savings may be possible with higher electricity rates, longer run hours or larger motor populations.

Unfortunately, new motor purchases are often based on availability or short-term economics, not evaluation and planning. By failing to specify higher efficiency motors, companies may miss out on the savings and other benefits.

Managing motors
Faced with competing priorities, plant managers may overlook the opportunity to manage their overall motor costs by effectively managing their motors. And as energy costs continue to rise, plant managers now more than ever need to take stock of the motors in their facilities. Motor management is one place to start.

Motor management is a set of strategies designed to help companies manage their motor populations more effectively by planning ahead for motor failure and incorporating life cycle costs in their decision-making process.

Successful motor management programs are based on some fundamental principles. The building blocks include:

• A motor survey and tracking program
• Guidelines for proactive repair/replace decisions
• A strategic spare-motor inventory for critical applications
• Purchasing and repair specifications
• Predictive and preventative maintenance programs

These principles, along with clear steps for implementation, are laid out in the Motor Planning Kit, one of many resources developed by the Motor Decisions Matter (MDM) campaign. MDM is a national public-awareness campaign sponsored by a diverse group of motor industry stakeholders.

Not having a motor management plan in place can lead to hasty decision-making when motor failure occurs, resulting in higher operating costs for years to come. In contrast, a sound motor management plan helps ensure that repair/replace decisions will be both quick and cost-effective.

One important consideration in the repair/replace decision making process is the use of NEMA Premium motors. As shown in the above example, with electricity costs running around 95 percent of total motor costs, it may be advantageous to specify more energy efficient motors.

Premium efficient motors
NEMA Premium is the most efficient motor designation in the marketplace today. Motors meeting this designation are approximately 1 to 4 percentage points more efficient than motors meeting 1992 EPAct standards, depending on the size and enclosure type.

In addition to energy savings, NEMA Premium motors have other valuable benefits. They generally contain more copper, are made with higher quality materials and have tighter tolerances, often resulting in cooler operating temperatures. This may help pro-long motor life and reduce maintenance costs, which in turn can help boost motor performance and productivity.

When considering a new motor purchase, the initial price of a NEMA Premium motor may be higher than its EPAct counterpart. However, it is also important to factor in how much a higher efficiency motor will save in electricity over its life time. MDM offers simple tools to demonstrate cost savings available with more efficient motors. Based on life-cycle costing, the 1-2-3 Approach software and the Estimated Annual Energy Savings Chart automatically calculate annual operating costs and energy savings for typical motors.

Premium efficient motors are just one way to help improve the bottom line through energy savings and possible improved productivity. Where appropriate, variable frequency drives (VFDs) offer another significant opportunity to reduce energy costs and improve performance.

Variable frequency drives
Many types of equipment do not need to operate at 100 percent capacity all the time. Motors running unnecessarily at full speed waste energy and cut into profits. VFDs can help by matching the motor’s speed to the load, allowing the motor to be continually adjusted relative to the power needed.

In addition to improved motor efficiency, VFDs can often reduce wear and tear on the motor and related components, which may not only reduce maintenance costs but possibly prolong the life of the motor. MidAmerican Energy Company, the largest utility in Iowa, worked with one customer on a VFD installation. The case study below highlights some of the benefits the customer has realized.

A Midwestern rubber manufacturer recently installed a VFD on a 1,500 HP motor used to power an extruder. The VFD not only helped save the company over $40,000 per year in utility bills, it also improved extruder operation. With the VFD, the unit can be brought online at very low revolutions per minute and ramped up, eliminating the need to shut down and clean out the unit after long idle periods. This procedure saves the customer more than 240 man-hours per year in labor costs.

To see the full case study, please visit www.motorsmatter.org. (MidAmerican provides service to electric and natural gas customers in South Dakota, Iowa and Illinois. For more information on MidAmerican’s motor programs, please visit their Web site at www.midamericanenergy.com/motors.)

When VFDs are used with variable torque loads, such as fans and pumps, the energy savings can be significant. Generally the best applications are large motors that can operate for many hours at reduced speed. It is important to talk with a motor service provider to determine whether a drive might be suitable for specific applications.

1-2-3…Go!
Now is the time to save energy, save money and improve plant operations.

Here are a few suggested steps to get going:

• Call a local motor service representative to discuss NEMA Premium motors, repair/replace strategies and other aspects of a motor management plan.

• Contact the local utility service provider to inquire about motor related programs in the area.

• Check out the tools and resources provided by the Motor Decisions Matter campaign.

The Motor Planning Kit, 1-2-3 Approach software, Energy Savings Chart and case studies are available at www.motorsmatter.org.

Motor Decisions Matter (MDM) is a national public-awareness campaign sponsored by motor manufacturers, National Electrical Manufacturers Association (NEMA), Electrical Apparatus Service Association (EASA) and other trade associations, electric utilities, the U.S. Environmental Protection Agency (EPA) and the Department of Energy (DOE). Managed by the Consortium for Energy Efficiency (CEE), MDM promotes energy-efficiency by encouraging commercial and industrial facility managers to use sound motor management as a tool to cut energy costs and increase productivity. It seeks to inform executives and other top-level decision makers about the potential bottom-line savings associated with sound motor planning and the purchase of NEMA Premium motors.

 Back to top                                       Back to Uptime archives