A variable frequency drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage of its power supply.
The VFD has the ability to control the ramp-up and ramp-down of the motor during start or stop respectively.

There are many reasons why we would want to adjust the speed of a motor.

Save energy and improve system efficiency.
Convert power in hybridization applications.
Match drive speed to process requirements.
low noise levels, for example from fans and pumps.
Reduce mechanical stress on machines to increase their life.

VFD applications

The use of VFDs in industrial and commercial applications.

In industrial applications-

VFDs are used to control the electric cranes, to roller coasters, and mechanical bulls.

In commercial applications-

VFDs are widely used in pumps to control flow and even volume in a tank, as well as in the HVAC industry.