Water and Wastewater Terms Beginning V

A B C D E F G H I J K L M N O P Q R S T U V W Y Z

variable frequency drive (VFD)

An electronic device that is used to vary the frequency of an electric current applied to motor. While the motor is not running, it is first connected to a low-frequency source; then, the frequency is incresaed gradually until the motor and pump (or other driven machine) are operating at the desired speed. This allows operators to precisely control the rotational speed of the motor.