Control of Electrical Drives

Electrical drives play an important role as electromechanical energy converters in transportation and most production processes. The ease of controlling electri cal drives is an important aspect for meeting the increasing demands by the user with respect to flexibility and precision, caused by technological progress in industry. Conversely, the control of electrical drives has in the past provided strong in centives to control engineering in general, leading to the development of new other areas of control. This is due to control structures and their introduction to stringent operating conditions and widely varying specifications - a drive may alternately require control of torque, acceleration, speed or position - and the fact that most electric drives have - in contrast to chemical or thermal pro cesses - well defined structures and consistent dynamic characteristics. During the last few years the field of controlled electrical drives has experi enced rapid expansion caused mainly by the advances of semiconductors in the form of power electronics as well as analogue and digital signal electronics, eventually culminating in microelectronics and microprocessors. The in troduction of electronically switched solid-state power converters has renewed the search for ac motor drives, not subject to the limitations of the mechanical commutator of de drives; this has created new and difficult control problems.