Consideration on Eddy Current Reduction Techniques for Solid Materials Used in Unconventional Magnetic Circuits

The use of solid materials in tubular, linear machines has significant manufacturing benefits, as this removes the need for an axially laminated stator. However, this comes at the cost of extra eddy current losses. In this paper, a detailed analysis of the behavior of eddy currents in a tubular permanent magnet machine that comprises unconventional magnetic circuit is given, highlighting the importance of the field distribution and current directions, when compared with conventional magnetic circuits. This analysis is then used to identify and investigate the appropriate eddy current reduction methods for tubular machines, when a solid material stator is being used. Accurate three-dimensional models have been built and then validated on previously built testing setups. Different winding configurations have been accounted. Finally, considerations of these techniques are given when being implemented into an actual, tubular machine design, highlighting the improved performance and losses

Passive electromagnetic damping device for motion control of building structures

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Architecture, 2005.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (leaves 112-115).The research presented in this thesis develops a new device for the passive control of motion in building structures: an electromagnetic damper. The electromagnetic damper is a self-excited device that provides a reaction force to an applied motion. We chose a tubular permanent-magnet linear machine as this new structural damper, and we derive its mathematical model using quasi-static electromagnetic theory. Computer simulations and experimental characterization of a small-scale prototype electromagnetic damper validated the mathematical model of the device. The behavior of the electromagnetic damper approximates that of an ideal damper. We conducted a feasibility study for the application of electromagnetic dampers to full-scale buildings. We used two performance measures: the damping density and the damping cost of the device. Comparing the performance of the electromagnetic damper to that of viscous fluid dampers, the maximum damping density of electromagnetic dampers is, at best, equal to that of hydraulic dampers, but with a price at least five times higher. The permanent magnet's current technology and cost are the limiting factors for the electromagnetic damper.(cont.) However, the electromagnetic damper provides flexibility not available previously to building designers as it can be used as a semi-active damper, as an actuator or as an energy regenerator without physical modifications to the device. Finally, we developed a design methodology for the electromagnetic damper to achieve a specified damping performance and introduced two techniques for the dynamic response analysis of buildings with electromagnetic dampers: One based on frequency domain approximations and one based on state-space models.by Rogelio Palomera-Arias.Ph.D