The Variable Frequency Driver (VFD) is a type of motor controller that changes the frequency and Powers of the electric motor by supplying voltage. Other names of the VFD are variable speed drive, adjustable speed drive, adjustable frequency drive, AC drive, micro drive and inverter.
The frequency (Hertz) is directly related to the speed of the motor (RPM). In other words, how much fast the frequency is, the torques (RPM) are much more. If the electric motor is not required to operate at full speed in an application, the VFD can be used to reduce frequency and voltage to load of current requirement of the electric motor. While the motor speed requirement changes, the VFD can simply increase or decrease speed requirements of motor.