In this book we deal with magnetic and electromagnetic devices. Specifically we discuss the theory, design, and analysis of linear motion electric actuators and generators. Whereas actuators are not precisely defined, we may consider them to be as devices which convert a form of energy into controlled mechanical motion. The form of energy may be electric, hydraulic, or pneumatic. In this book we are concerned with electric actuators, which convert electric energy into controlled mechanical motion of limited travel. Electric actuators compare favorably with hydraulic and pneumatic actuators, and are much superior to both in terms of efficiency, controllability, cost, and environmental safety. Of course, electric actuators may be either rotary generating rotary motion or linear leading to linear motion. Furthermore, a linear electric actuator may be direct operating, utilizing electromagnetic or piezoelectric effects to produce force and motion. On the other hand, a converting type of linear actuator uses an electric motor with gears and linkages to produce linear motion. The direct operating type of linear actuators are the subject matter of this book. Most of these devices invariably consist of coupled magnetic and electric circuits in relative motion, although piezoelectric actuators operate on a different principle.

Because the electromechanical energy conversion process is reversible, actuators may be operated as linear electric generators, in which case mechanical energy is transformed into electric energy.