Among the most successful strategies managers have at their disposal for controlling electrical energy use and minimizing utility costs is the use of variable frequency drives
. Incorporating variable frequency drives into applications such as fans, pumps, and cooling towers can reduce energy use up to 50 percent at partial loads by matching motor speed to the changing load and system requirements.
Advances in variable frequency drive technology are putting even more power in the hands of maintenance and engineering managers, who are taking a closer look at the life-cycle costs and potential benefits of variable frequency drive applications for their facilities.
Technology Drives Forward
Electric motors' driving equipment, such as pumps and fans, normally operate at a constant speed. Some form of mechanical throttling — a valve on the outlet, in the case of a pump, or the slats in a louver, in the case of a fan — controlled the water or airflow speed and volume.
Using these flow-control methods, the motor continues to operate at full speed and uses electric energy at the full-load rate, even though it was performing less useful work. In the process, it wasted a great deal of energy.
have introduced a more efficient way to provide load control when the load varies, which is most of the time when moving fluids.
The two most commonly used methods to vary speed electrically, rather than mechanically, depend on whether the drive is alternating current (AC) or direct current (DC). If it is AC, which encompasses most motors, varying the frequency of the electrical energy supplied to the motor controls the speed. Examples include AC motors
driving fans, pumps, and compressors.
Registration date: Oct 31, 2013