Design of a New Type of Eddy Current Damper With Increased Damping Density

2009 ◽  
Author(s):  
Lei Zuo ◽  
Brian Scully ◽  
Samir Nayfeh
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
High Efficiency ◽  
High Reliability ◽  
Large Mass ◽  
Damping Force ◽  
Eddy Current Damper ◽  
New Type ◽  
Packing Size ◽  
The Magnetic Field

Eddy current dampers have advantages of no mechanical contact, high reliability and stability, but also suffer from the disadvantage of large mass and packing size. In this paper we present a new type of eddy current damper with remarkable high efficiency and compactness. Instead of orienting the magnetic field in a uniform direction, we split the magnetic field into multiple ones with alternative directions so as to reduce the electrical resistance of the eddy current loops and thus to increase the damping force. Experimental results demonstrate that an eddy current damper of 100 × 150 × 140 mm3 has a damping coefficient nearly 3000 Ns/m. The damping density [Ns/m/m3] and dimensionless damping constant are 3–7 times higher than those in literature.

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

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Lei Zuo ◽  
Xiaoming Chen ◽  
Samir Nayfeh
Keyword(s):  
Magnetic Field ◽  
Analytical Model ◽  
Eddy Current ◽  
High Efficiency ◽  
High Reliability ◽  
Damping Force ◽  
Element Analysis ◽  
Eddy Current Damper ◽  
New Type ◽  
The Magnetic Field

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.

Modeling of Eddy Current Damper Composed of Spherical Magnet and Conducting Shell

2006 ◽  
Author(s):  
Yoshihisa Takayama ◽  
Atsuo Sueoka ◽  
Takahiro Kondou
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Magnetic Force ◽  
Eddy Currents ◽  
Reaction Force ◽  
Damping Force ◽  
Magnetic Damping ◽  
Conducting Plate ◽  
Direction Of Movement ◽  
Eddy Current Damper

If a conducting plate moves through a nonuniform magnetic field, eddy currents are induced in the conducting plate. The eddy currents produce a magnetic force of drag, known as Fleming's left-hand rule. This rule means that a magnetic field perpendicular to the direction of movement generates a magnetic damping force. We have fabricated the eddy current damper composed of the spherical magnet and the conducting shell. The spherical magnet produces the axisymmetric magnetic field, and the shape of the conducting shell appears to combine a semispherical shell conductor and a cylinder conductor. When the eddy current damper works, the conducting shell is fixed in space, and the spherical magnet moves under the conducting shell. In this case, since there are magnetic flux densities perpendicular to the direction of movement, eddy currents flow inside the conducting shell, and then a magnetic force is produced. The reaction force of this magnetic force acts on the spherical magnet. In our study, eddy current dampers composed of a magnet and a conducting plate have been modeled using infinitesimal loop coils. As a result, magnetic damping forces are obtained. Our modeling has three merits as follows: the equation of a magnetic damping force is simple in the equation, we can use the static magnetic field obtained using FEM, the Biot-Savart law or experiments and the equation automatically satisfies boundary conditions using infinitesimal loop coils. In this study, we explain simply the principle of this method, and model an eddy current damper composed of a spherical magnet and a conducting shell. The analytical results of the modeling agree well with the experimental results.

Analysis and Experimental Evaluation of Inherent Instability in Electromagnetic Eddy-Current Dampers Intended for Reducing Lateral Vibration of Rotating Machinery

1995 ◽  
Author(s):  
Yuri Kligerman ◽  
Asif Grushkevich ◽  
Mark S. Darlow ◽  
Adrian Zuckerberger
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
High Speed ◽  
Experimental Tests ◽  
Rotating Machinery ◽  
Lateral Vibration ◽  
Negative Effect ◽  
Eddy Current Damper ◽  
Analytical Approaches ◽  
The Magnetic Field

Abstract There have been a number of papers published that concern the design and operation of electromagnetic, eddy-current dampers for controlling lateral vibration of rotating machinery. Many of these papers have included analysis approaches and all have been generally effective for low-speed operations. There have been a few reports concerning high-speed (supercritical) operations and many of these have indicated instability problems, but none of these have provided a valid analysis to account for instability. That is, all of the analytical approaches have ignored the disk rotation, relative to the magnetic field, and no obvious sources of instability have been found. In this paper, we will present our work in which we have rederived the analyses of this system in which we have not made the common assumption of no rotation between the disk and the magnetic field. In this case, the potential of instability for supercritical speed operation is clear and, in fact, the equivalent negative damping contribution of the eddy-current damper, under these conditions, has a negative effect on the system even if not fully unstable. We have carefully performed a series of experimental tests which corroborate this analytical approach. Finally, we briefly discuss alternative eddy-current damper design approaches that could be considered to provide effective damping at all speeds and avoid these instability problems.

Analytical and Experimental Evaluation of Instability in Rotordynamic System With Electromagnetic Eddy-Current Damper

1998 ◽  
Vol 120 (1) ◽  
pp. 272-278 ◽  
Author(s):  
Y. Kligerman ◽  
A. Grushkevich ◽  
M. S. Darlow
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
High Speed ◽  
Experimental Tests ◽  
Disk Rotation ◽  
Negative Effect ◽  
Eddy Current Damper ◽  
All Speeds ◽  
Analytical Approaches ◽  
The Magnetic Field

There have been a number of papers published that concern the design and operation of electromagnetic, eddy-current dampers for controlling lateral vibration of rotating machinery. Many of these papers have included analysis approaches and all have been generally effective for low-speed operations. There have been a few reports concerning high-speed (supercritical) operations and many of these have indicated instability problems, but none of these have provided a valid analysis to account for instability. That is, all of the analytical approaches have ignored the disk rotation, relative to the magnetic field, and no obvious sources of instability have been found. In this paper, we will present our work in which we have rederived the analyses of this system in which we have not made the common assumption of no rotation between the disk and the magnetic field. In this case, the potential of instability for supercritical speed operation is clear and, in fact, the equivalent negative damping contribution of the eddy-current damper, under these conditions, has a negative effect on the system even if not fully unstable. We have carefully performed a series of experimental tests which corroborate this analytical approach. Finally, we briefly discuss alternative eddy-current damper design approaches that could be considered to provide effective damping at all speeds and avoid these instability problems.

Model of Eddy Current Damping Mechanism for the Suppression of Beam Vibrations

Aerospace ◽  
2004 ◽  
Author(s):  
Henry A. Sodano ◽  
Jae-Sung Bae ◽  
Daniel J. Inman ◽  
W. Keith Belvin
Keyword(s):  
Magnetic Field ◽  
Theoretical Model ◽  
Eddy Current ◽  
Damping Ratio ◽  
Power Supplies ◽  
Damping Force ◽  
Electromagnetic Damping ◽  
Eddy Current Damping ◽  
Eddy Current Damper ◽  
External Power

The movement of a conductor through a stationary magnetic field or a time varying magnetic field through a stationary conductor generates electromagnetic forces that can be used to suppress the vibrations of a flexible structure. In the present study, a new electromagnetic damping mechanism is introduced. This mechanism differs from previously developed electromagnetic braking systems and eddy current dampers because the system investigated in the following manuscript uses the radial magnetic flux of a permanent magnet to generate the electromagnetic damping force rather than the flux perpendicular to the magnet’s face as done in other studies. One important advantage of the proposed mechanism is that it is simple and easy to be applied. Additionally, a single magnet can be used to damp the transverse vibrations that are present in many structures. Furthermore, it doesn’t require any electronic devices or external power supplies, therefore functioning as a non-contacting passive damper. A theoretical model of the system is derived using electromagnetic theory, enabling us to estimate the electromagnetic damping force induced on the structure. The proposed eddy current damper was constructed and experiments were performed to verify the precision of the theoretical model. It is found that the proposed eddy current damping mechanism increases the damping ratio by up to 150 times and provides sufficient damping force to quickly suppress the beam’s vibration.

STUDY OF PHASE PROPAGATION IN SUPERCONDUCTING ALUMINUM BY ULTRASONIC ATTENUATION MEASUREMENTS

1959 ◽  
Vol 37 (5) ◽  
pp. 614-618 ◽  
Author(s):  
K. L. Chopra ◽  
T. S. Hutchison
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Ultrasonic Attenuation ◽  
Cylindrical Specimen ◽  
Current Theory ◽  
Superconducting Phase ◽  
Rate Of Change ◽  
Time Rate ◽  
Phase Propagation ◽  
The Magnetic Field

The phase propagation in superconducting aluminum has been studied by measuring the time rate of change of ultrasonic attenuation. The time taken for the destruction of the superconducting phase in a cylindrical specimen, by means of a magnetic field, H, greater than the critical field, Hc, is approximately proportional to{H/(H–Hc)} in agreement with eddy-current theory. In the converse case, where the superconducting phase is restored by switching off the magnetic field H (>Hc), the total time taken is nearly independent of the temperature (or Hc) as well as H. The superconducting phase grows at a non-uniform volume rate which is considerably less than the uniform rate of collapse.

scholarly journals Radio Emission Model of a 'Typical' Pulsar

1987 ◽  
Vol 40 (6) ◽  
pp. 755 ◽  
Author(s):  
AZ Kazbegi ◽  
GZ Machabeli ◽  
G Melikidze
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Waves ◽  
Emission Model ◽  
Radio Waves ◽  
Resonance Case ◽  
Pulsar Magnetosphere ◽  
Pulsar Emission ◽  
Dipole Magnetic Field ◽  
New Type ◽  
The Magnetic Field

The generation of radio waves in the plasma of the pulsar magnetosphere is considered taking into account the inhomogeneity of the dipole magnetic field. It is shown that the growth rate of the instability of the electromagnetic waves calculated in the non-resonance case turns out to be of the order of 1/ TO (where TO is the time of plasma escape from the light cylinder). However, the generation of electromagnetic waves from a new type Cherenkov resonance is possible, occurring when the particles have transverse velocities caused by the drift due to the inhomogeneity of the magnetic field. Estimates show that the development of this type of instability is possible only for pulsars with ages which exceed 104 yr. We make an attempt to explain some peculiarities of 'typical' pulsar emission on the basis of the model developed.

Quantitative Research on Cracks in Pipe Based on Magnetic Field Response Method of Eddy Current Testing

2021 ◽  
Vol 36 (1) ◽  
pp. 99-107
Author(s):  
Feng Jiang ◽  
Shulin Liu ◽  
Li Tao
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Quantitative Research ◽  
Three Dimensional ◽  
Impedance Analysis ◽  
Eddy Current Testing ◽  
Element Analysis ◽  
Defect Parameter ◽  
Current Testing ◽  
The Magnetic Field

The quantitative evaluation of defects in eddy current testing is of great significance. Impedance analysis, as a traditional method, is adopted to determine defects in the conductor, however, it is not able to depict the shape, size and location of defects quantitatively. In order to obtain more obvious characteristic quantities and improve the ability of eddy current testing to detect defects, the study of cracks in metal pipes is carried out by utilizing the analysis method of three-dimensional magnetic field in present paper. The magnetic field components in the space near the crack are calculated numerically by using finite element analysis. The simulation results confirm that the monitoring of the crack change can be achieved by measuring the magnetic field at the arrangement positions. Besides, the quantitative relationships between the shape, length of the crack and the magnetic field components around the metal pipe are obtained. The results show that the axial and radial magnetic induction intensities are affected more significantly by the cross-section area of the crack. Bz demonstrates obvious advantages in analyzing quantitatively crack circumference length. Therefore, the response signal in the three-dimensional direction of the magnetic field gets to intuitively reflect the change of the defect parameter, which proves the effectiveness and practicability of this method.

Design of TSV-based Inductors for Internet of Things

2016 ◽  
Vol 2016 (DPC) ◽  
pp. 002111-002130 ◽  
Author(s):  
Bruce C Kim ◽  
Saikat Mondal
Keyword(s):  
Magnetic Field ◽  
Internet Of Things ◽  
Power Electronics ◽  
Eddy Current ◽  
Electronics Packaging ◽  
High Density ◽  
Metal Core ◽  
The Core ◽  
Iot Applications ◽  
The Magnetic Field

This paper describes the design of a Through Silicon Via based high density 3D inductors for Internet of Things (IoT) applications. We present some possible challenges for TSV-based inductors in IoT applications. The current trend towards Internet of Things (IOT), System in Package (SiP) and Package-on-Package (PoP) requires meeting the power requirements of heterogeneous technologies while maintaining minimum package size. 3-D chip stacking has emerged as one of the potential solutions due to its high density integration in a 3D power electronics packaging regime. As an integral part of many power electronics applications, TSV-based inductors are becoming a popular choice because of their high inductance density due to the reduced on-chip footprint compared to conventional planar inductors. Depending on the requirement, values of these inductors could range from a few nanohenries to hundreds of microhenries. Small inductors with a high quality factor are mainly used for RF filter applications, whereas large inductors are used in power electronics packaging. For high inductance it is necessary to use ferromagnetic materials. A conventional ferromagnetic metal core like nickel could offer high permeability, which can help to boost the inductance. However, the magnetic field lines within a metal core induce eddy current which can have multiple adverse effect in power electronics packaging. For example, it has long been known that the current can increase the resistance in transformer winding [1]. Eddy current can also heat up the core of the inductor which makes the heat sink process in 3D packaging even more challenging. One way to decrease the eddy current, is to pattern and laminate the core block into multiple segments orthogonal to the direction of the magnetic field line [2]. Another method is to increase the resistivity of the core material so that the eddy current is limited to a very small magnitude [3].

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