As electricity costs rise, lifecycle cost analysis of motors is influencing more buying decisions, says Baldor's John Malinowski, motor product manager. Consider that over a motor's life, 97.3% of the cost of owning and operating the unit will be for electrical power. With 0.7% allocated for one rewind, that leaves the initial purchase represented by only 2% of the lifetime cost. Here are Malinowski's suggestions on how to start pursuing energy efficiency:
Do a complete motor survey of the facility. List the motors that drive machinery such as conveyors, fans, pumps and machining centers. That will provide a benchmark to determine how much power your electric motors are using.
Upgrade to premium efficient motors wherever possible. The initial price of a motor is approximately 2% of the lifetime costs of operation; therefore it usually pays to purchase the highest efficiency possible. Premium efficient motors often pay for themselves in energy efficiency within the first three years, then continue saving energy for years to come.
How much can you save by upgrading? A 100-hp motor operating continuously with an 85% efficiency rating would use 768,820 kWh (kilowatt-hours) of electricity annually. If you upgrade to a premium efficient motor rated at 95.4%, you could save 83,810 kWh of energy annually. At 7.5 cents per kWh this would mean an annual energy savings of $6,285.75.
Use the "right" motor size for the application. Over time motors in older applications tend to migrate upwards to a higher horsepower rating than is needed. At other times the application's power demand increases and the motor may be undersized for the new load. In either case, energy is wasted. The motor's efficiency and power factor drops off when operated outside of its design load rating of 75% to 100% of the motor's rated load.
John Malinowski, motor product manager, Baldor
Turn off motors when they are not needed. Motors that are turned off use no energy. In some applications, reducing motor operating time by just 10% can save as much energy as upgrading to a premium efficient motor. Motors are designed to be started and stopped. The myth that this will reduce the life of the motor is incorrect unless it exceeds the design-starting specification.
Establish a motor management plan. Motor management is often employed as an MRO management technique. It is far better to know which motors are critical to your operation and what to do about them if there is a failure or impending failure before it occurs. Take into consideration the economic and reliability benefits of upgrading to premium efficient motors whenever possible.
Basic techniques have been developed to determine if the motor should be repaired or replaced if a failure occurs. These techniques can be incorporated as rules of thumb into the plan. Often a permanent identification tag is attached to each motor, which describes the motor and its replacement part number, and tells the technician what to do to the motor when a failure occurs.