MAKING THE PROPER CHOICE OF ADJUSTABLE-SPEED DRIVES.

This paper reviews five types of adjustable-speed drives which predominate in process plants. They include: solid-state ac - the drive that is rapidly gaining widespread favor because it saves energy; solid-state dc - the drive that is still the most common in industry overall; mechanical - the simplest answer for many operations calling for variable speed; electromechanical - the choice for some services where precise, fast-changing speed control is critical; and fluid - a rugged drive for handling large loads. New concepts of adjustable-speed drives have been developed because of energy conservation considerations.