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Mechanical / HVACaka: VFDaka: adjustable frequency driveaka: variable speed driveaka: AFD

Variable Frequency Drive

In Plain English

An electronic controller that slows down motors on fans and pumps to save energy when full speed is not needed.

Definition

An electronic device that controls the speed of an AC electric motor by varying the frequency and voltage of the power supplied to it. Variable frequency drives (VFDs) are used on HVAC fans, pumps, and compressors to match equipment output to actual system demand, dramatically reducing energy consumption. Reducing a fan to 50 percent speed cuts power consumption to approximately 12.5 percent due to the cube law relationship between speed and power.

Example

VFDs on the chilled water pumps reduce motor speed from 100 percent to 60 percent during low-load periods, cutting pump energy use by 78 percent.

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