BUYING AN ENERGY-EFFICIENT ELECTRIC MOTOR (8)

8. How should I begin a motor efficiency improvement program?

Survey your motors. Gather nameplate information and obtain field measurements (voltage, amperage, power factor, operating speed) under typical operating conditions.

Initially focus on motors that exceed minimum size and operating duration criteria. Typical selection criteria include:
• Three-phase NEMA design B motor
• Non-specialty motor
• 10 to 600 hp
• At least 2000 hours per year of operation
• Constant load (not intermittent, cyclic, or fluctuating)
• Older or rewound standard efficiency motors
• Easy access
• Readable nameplate.


Conduct motor replacement analyses (with MotorMaster+) and divide your motors into the following three categories:

Replace Immediately — Motors Offering Rapid Payback through Energy Savings, Improved Reliability, or Utility Rebates. These include motors that run continuously (typically 8000 or more hours a year), are currently inefficient (including oversized motors), must be reliable, or are covered by attractive utility rebate programs. Order an efficient replacement motor soon and install it at the next available opportunity, such as during a scheduled downtime.

Replace at Time of Failure — Motors with Intermediate Payback. When these motors fail, you will want to replace them with an energy-efficient model. Now is the time to contact motor dealers to review the efficiency and prices of available motors. After identifying the most cost-effective replacement model, you must decide whether to purchase it and keep it on hand as a spare, or wait to purchase it until the existing motor fails. This choice depends on how quickly an energy-efficient motor can be obtained through suppliers, how quickly a failed motor must be replaced, and how many motors of the same size and type are used in your facility.

Leave Present Situation as is — Motors with Extended Payback. These motors are already reasonably efficient or are used less than 2000 hours each year. They can be rewound or replaced with a similar motor.

Motors and drive systems have a long useful life. The cost of running a motor may increase significantly in the future. Energy efficiency improvements that are not justified today may become worthwhile in a few years, so periodically reevaluate paybacks and reliability. It is also important to operate your motor efficiently. Keep the following two issues in mind:

Power Quality. Address power quality problems. To improve motor reliability and efficiency, it is important to maintain the correct voltage and phase balance, identify and eliminate current leaks, and prevent harmonics in the electrical supply. It is a good idea to have an electrical engineer review the electrical system periodically, especially before installing a new motor or after making changes to the system and its loads. Consult the manufacturer before installing any motor under conditions of poor power quality.

Periodic Maintenance. It is important to maintain motors according to manufacturers’ instructions. Although energy-efficient motors with higher temperature-rated insulation may be able to handle higher temperatures and other abuse, there is no reason to reduce maintenance. Motors should have good ventilation and be periodically inspected for increased vibration or power supply problems.

to be continued………

Source : Fact Sheet – US Department of Energy

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