A Variable Speed Drive (VSD) is an electronic equipment that regulates the speed and torque output of an electric motor. They are used for two major goals:

• Process Control: to match the motor speed to the required tasks and also to compensate the changes;
• Energy Conservation: using the specific value of rotational speed for each application it’s possible to save energy (for example by adjusting the speed of a cooling fan motor to match the temperature of the machinery parts it is cooling).

Historically, adjustable speed drives were developed for process control, but energy conservation has emerged as an equally important objective.

The process control benefits provided by the use of a variable speed drive are:

• Smoother operation;
• A better acceleration control of the motor;
• Possibility to use the same motor with different speed for various process requirements;
• Compensate for changing process variables;
• Slow operation useful for setup purposes;
• Accurate positioning;
• Torque Control.