Manufacturers Best Practice Guide
Motors: Basics
The U.S. Department of Energy estimates that motor systems consume approximately 64% of electricity used by the industrial sector. Motor applications vary as widely as the businesses they serve, but common uses include fans, pumps, compressors, and conveyance.
Motors can be incredibly efficient. A well-designed and well-maintained motor system can reach 90% efficiency - meaning that 90% of the input energy gets converted to useful work. Unfortunately, only a small portion of the U.S. motor inventory falls into this category. Poorly maintained motors and fans, load incompatibility and inefficient motors are commonplace and there is ample room for improvement, especially as older motors are retired and replaced. The American Council for an Energy-Efficient Economy (ACEEE) estimates that optimization of electric motor performance can save as much as 25% of total U.S. electricity use. For individual manufacturers, motor drive optimization potentially saves as much as 50% of motor energy use - a significant amount when you consider that motor energy costs can exceed $1 million per year in large industrial plants.
Replacing Worn Motors
Since motors can last as long as 30 years, it is important to replace retired motors quickly, with the most cost-effective new model. Keep regular maintenance records that indicate which motors might be underperforming or otherwise malfunctioning. Be prepared beforehand by comparing the lifecycle costs of different potential replacement motors, and then determine which option is the most cost-effective for your needs. If you have the resources, consider purchasing and storing the replacement motor before the worn motor dies to help minimize any downtime.
Purchasing motors and drives
Work with your purchasing department to create a general purchasing policy that specifies premium efficiency motors. Purchasing personnel may also be helpful in calculating the cost-benefit of different options, and working with motor vendors.
If you have avoided premium-efficiency motors because of higher upfront costs, consider that in some cases utility savings are so great that equipment pays for itself in a matter of months.
Irrigation and other pumps tend to be inefficient whenever overloaded or underloaded. Try to match drive size as closely as possible to expected loads. Dip below 50% load for any pump, and efficiency generally plummets.
If pump loads fluctuate widely or if pumps are often run at partial loads, adding a variable-speed drive may be cost effective since it closely matches output to actual demand. VSD-based pumping systems tend to work best with time-of-use billing schedules and on deep wells with frequent stop-and-start pumping. A quality VSD can help cut down on motor noise, improve production efficiency and eliminate the "voltage sags" (often evident from temporarily dimmed lights) common to motor startup, meaning that the benefits of VSDs extend well beyond just energy savings.
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Leading by Example: California Portland Cement Company
California Portland Cement plants mandate that all new motor replacements meet the latest National Electrical manufacturers Association premium efficiency standards. They are evaluating pneumatic pump efficiencies and implementing a retrofit program to install new high-efficiency compressor motors and drives throughout the company. They are also proactively replacing V-belts with cog or synchronous belts on motor drives, which can improve efficiency by 3% to 5% over V-belts. These measures are helping California Portland Cement cut energy use and save money.