As recently as a few decades ago, manufacturers assumed that energy costs were simply an uncontrollable cost. But such attitudes became outdated with the advent of variable speed drives and power-monitoring technologies capable of making energy a manageable expense -- one that can be controlled by adjusting key processes to use less energy.

The ability to save energy today is considered a given in industrial settings, with tools and techniques to limit energy expenditures now including motor controllers, software, and power monitoring and control devices capable of reducing energy costs and helping manufacturers control costs better than before.

Domestic manufacturers annually spend more than $33 billion on electricity, with motor systems consuming approximately 63% of all electricity. More than half of those motors are used in either fan or pump applications -- key areas with phenomenal potential for energy savings.

Most fan applications do not require the full amount of air movement that fans are designed to produce. So, to vary airflow, fan applications use methods such as:

• cycling (generally used in residential settings and not applicable in industrial settings),


• outlet dampers,


• variable inlet vanes, and


• variable speed drives.

In industrial settings, variable speed/ac drives are generally the most effective means of controlling energy use because they control actual motor speed. Methods such as inlet vanes and outlet dampers only control the amount of air an application receives, not motor speed.

Variable speed drives also can contribute to energy savings for pump applications. Controlling the speed of a pump is accomplished either through throttling the motor (mechanically changing the pump's speed) or employing a drive to control the motor's speed -- and, therefore, the amount of energy used by the pump motor.

Top Five Ways to Save Energy with AC Drives

1. Variable torque loads like centrifugal fans and pumps benefit greatly from ac drives because power draw varies with the cube of speed change. Energy savings are tremendous as speed is decreased. Achieving flow change by methods other than speed change (e.g. valves, dampers, or vanes) offers far less energy savings.

2. For constant torque loads, conversion from mechanical drives (sheaves and gears) can also offer large energy savings because, on average, they are less efficient than electronic drives. In this case, the savings are magnified at larger loads.

3. For loads that must shed energy often (centrifuges, punch presses, winders) regenerative electronic drives can deliver power back to the power system instead of wasting the energy in braking mechanisms. Again, the larger the load, the greater the savings.

4. Electronic drives inherently operate to start loads softly, which not only reduces mechanical stress but can also save extra power charges for peak demand. Most ac electronic drives also improve displacement power factor, which many power companies charge extra for.

5. Many electronic drives offer a special energy-saver mode, which reduces applied voltage under lightly loaded conditions. Although the additional savings are small in comparison to the others listed, large power installations can achieve meaningful savings.