Permanent magnet configuration in design of an eddy current damper

Abstract

This paper discusses the design of an eddy current passive damper using different configurations of permanent magnets. Motional eddy current damping effect is used for the development of a passive damper. Eddy currents are generated in a conductor in a time-varying magnetic field. They are induced either by movement of the conductor in a static field or by changing the strength of the magnetic field, initiating motional and transformer electromotive forces, respectively. The conceived eddy current damper consists of a conductor as an outer tube, and an array of axially magnetized, ring-shaped permanent magnets (PMs), separated by iron pole pieces as a mover. The relative movement of the magnets and the conductor causes the conductor to undergo motional eddy currents. Using this concept, damping characteristics of the new damper is obtained through analytical modeling, and verified by experimental analysis. The optimum PMs' size and configuration are also derived using analytical and finite element analysis, respectively. A damping coefficient as high as 53 kg/s is achievable with the proposed design specifications.

A hybrid electromagnetic shock absorber for active vehicle suspension systems

“…As mentioned earlier, the axially magnetised PMs in the mover are utilised, achieving a higher thrust force density and higher efficiency than other candidate topologies [20]. This topology also has advantages for ease and cost of manufacturing.…”

“…The assembly comprises a tubular design, as shown in Figure 1, which has less leakage flux compared with the flat design, and is vastly better in utilising the magnetic flux, leading to a higher induced electromotive force (emf) (in the generator mode) and a higher thrust force (in the actuator mode). Axially magnetised PMs in the mover result in a higher force-to-volume ratio rather than radially magnetised ones [20].…”

Magnetic forces between arrays of cylindrical permanent magnets

“…Recently, permanent magnet arrays have been utilized in many applications; among others: eddy current dampers [1,2], magnetic refrigerators [3,4], micropumps [5]. Furthermore, the repulsive force between permanent magnets and superconducting samples is utilized for levitation [6].…”

Design and Damping Analysis of a New Eddy Current Damper for Aerospace Applications

“…Kwag et al (2007) and Bae et al (2009) propose and develop an eddy current shock absorber by using a permanent magnet in a conductive tube and discuss it is more effective than Sodano's model because the radial flux is almost perpendicular to the copper tube surface. Ebrahimi et al (2008Ebrahimi et al ( , 2010 design and analyze an eddy current passive damper with different configurations of permanent magnets. Its damping characteristics are obtained through analytical modeling and verified by experimental works.…”