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Research Papers

# Design and Analysis of a New Type of Electromagnetic Damper With Increased Energy Density

[+] Author and Article Information
Lei Zuo

Department of Mechanical Engineering, State University of New York at Stony Brook, Stony Brook, NY 11794lei.zuo@stonybrook.edu

Xiaoming Chen

Department of Mechanical Engineering, State University of New York at Stony Brook, Stony Brook, NY 11794

Samir Nayfeh

Equilibria Corporation, 472 Amherst Street, Nashua, NH 03063

J. Vib. Acoust 133(4), 041006 (Apr 07, 2011) (8 pages) doi:10.1115/1.4003407 History: Received October 17, 2009; Revised November 03, 2010; Published April 07, 2011; Online April 07, 2011

## Abstract

Eddy current dampers, or electromagnetic dampers, have advantages of no mechanical contact, high reliability, and stability, but require a relatively large volume and mass to attain a given amount of damping. In this paper, we present the design and analysis of a new type of eddy current damper with remarkably high efficiency and compactness. Instead of orienting the magnetic field in a uniform direction, we split the magnetic field into multiple ones with alternating directions so as to reduce the electrical resistance of the eddy current loops and increase the damping force and damping coefficient. In this paper, an analytical model based on the electromagnetic theory for this type of eddy current damper is proposed, and a finite-element analysis (FEA) is carried out to predict the magnetic field and current density. Experimental results agree well with the analytical model and FEA predictions. We demonstrate that the proposed eddy current damper achieves a damping density $(N s/m m3)$ and a dimensionless damping constant as much as 3–5 times as those in the literature. The dependence of damping on velocity and frequency is also examined.

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Copyright © 2011 by American Society of Mechanical Engineers
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## Figures

Figure 1

Illustration of two types of arrangements of magnetic field for eddy current dampers: case (a) uniform magnetic field and case; (b) alternating magnetic field

Figure 2

(a) Eddy current damping of a moving conductor and (b) electric field due to eddy current

Figure 3

Electric field distribution of the conductor plate in (a) unidirectional magnetic field and (b) alternating magnetic field

Figure 4

Illustration of eddy current in a conductor plate moving in an array of alternating magnetic field

Figure 5

Design of a new type of magnetic eddy current damper: (a) assemblies of magnetic array and conductor plates and (b) top view of magnet array

Figure 6

Finite-element analysis of magnetic field: (a) top view of magnetic flux loops and (b) magnetic flux density B on the conductor plane

Figure 7

The eddy current density of a moving conductor plate inside a magnetic field: (a) with alternative pole arrangement and (b) unidirectional magnetic field, where the relative velocity is 0.02 m/s

Figure 8

Measured and calculated magnetic flux intensities along the center of magnets in the horizontal and vertical directions: measured (solid), calculated for static field (dashed), and calculated for the case when the conductors move at a velocity of 0.2 m/s (dot and dashed dot).

Figure 9

(a) Time histories of displacement and damping force and (b) force-displacement damping loops

Figure 10

(a) Schematic view of the vibration system and (b) a vibration system damped with the eddy current damper

Figure 11

(a) Frequency response and (b) time history of the vibration system for ωn=67.5 Hz: with eddy current damping (solid) and without eddy current damping (dashed)

Figure 12

Frequency dependence of damping coefficients

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