Design and Control for Linear Machines, Drives, and MAGLEVs—Part I

Rotating electric machines have existed for more than 150 years. Their linear counterpart, called linear electric (electromagnetic) machines (LEMs), were introduced at the turn of the last century. They have been conceived to convert electrical energy into mechanical energy (or vice versa) as a direct linear motion through electromagnetic forces. LEMs are reversible devices, meaning that they can work as both motors and generators. Although feasible, li near alternators are currently explored for limited applications (e.g., Stirling motor). On the contrary, linear motors or actuators are electromagnetic devices capable of producing direct (without any link or interposition) li ear motions of the following types: in a unique direction, short -stroke motion, oscillatory motion, and step-by-step motion. Correspondingly, exactly as in the rotating counterpart, different types of linear motors have been devised: linear synchronous motors (LSMs) in its versions with excitation winding, with permanent magnets (PMs) LSMs or without both (linear reluctance motor = LRM), linear induction motors (LIIVls), and linear stepper motors.