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)

A control system that allows the frequency of the current applied to a motor to be varied. The motor is connected to a low-frequency source while standing still; the frequency is then increased gradually until the motor and pump (or other driven machine) are operating at the desired speed.