A VSD is a type of adjustable-speed drive used in electro-mechanical drive systems to control AC motor speed and torque.
There are many and diverse reasons for using variable speed drives. Some applications, such as paper making machines, cannot run without them while others, such as centrifugal pumps, can beneﬁt from energy savings.
The beneﬁts of energy savings are not always fully appreciated by many users. These savings are particularly apparent with centrifugal pumps and fans, where load torque increases as the square of the speed and power consumption as the cube of the speed
In general, variable speed drives are used to:
Latch the speed of a drive to the process requirements
Latch the torque of a drive to the process requirements
Save energy and improve efficiency
The needs for speed and torque control are usually fairly obvious.