Modeling of a New Active Eddy Current Vibration Control System

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Henry A. Sodano ◽  
Daniel J. Inman
Keyword(s):  
Magnetic Field ◽  
Vibration Control ◽  
Electric Fields ◽  
Eddy Current ◽  
Eddy Currents ◽  
Vibration Suppression ◽  
Frequency Doubling ◽  
Damping Force ◽  
Theoretical Derivation ◽  
Eddy Current Damping

There exist many methods of adding damping to a vibrating structure; however, eddy current damping is one of few that can function without ever coming into contact with that structure. This magnetic damping scheme functions due to the eddy currents that are generated in a conductive material when it is subjected to a time changing magnetic field. Due to the circulation of these currents, a magnetic field is generated, which interacts with the applied field resulting in a force. In this manuscript, an active damper will be theoretically developed that functions by dynamically modifying the current flowing through a coil, thus generating a time-varying magnetic field. By actively controlling the strength of the field around the conductor, the induced eddy currents and the resulting damping force can be controlled. This actuation method is easy to apply and allows significant magnitudes of forces to be applied without ever coming into contact with the structure. Therefore, vibration control can be applied without inducing mass loading or added stiffness, which are downfalls of other methods. This manuscript will provide a theoretical derivation of the equations defining the electric fields generated and the dynamic forces induced in the structure. This derivation will show that when eddy currents are generated due to a variation in the strength of the magnetic source, the resulting force occurs at twice the frequency of the applied current. This frequency doubling effect will be experimentally verified. Furthermore, a feedback controller will be designed to account for the frequency doubling effect and a simulation performed to show that significant vibration suppression can be achieved with this technique.

Analysis and Modeling of Eddy Current Damping for Short-Stroke DC Linear Motor

2013 ◽  
Vol 416-417 ◽  
pp. 300-304
Author(s):  
Dong Hua Pan ◽  
Jia Xi Liu ◽  
Feng Jing Shen ◽  
Li Yi Li ◽  
Ming Na Ma
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Eddy Currents ◽  
Linear Motor ◽  
Force Model ◽  
Equivalent Resistance ◽  
Damping Force ◽  
Conductive Material ◽  
Charge Model ◽  
Eddy Current Damping

Eddy currents induced in a conductor in a changing magnetic field produce a damping force proportional to the heat generated in the conductive material. In this paper, the damping force of short-stroke DC Linear Motor (DCLM) is researched, and then model of damping force is established. In the preliminary work, the analytical expression of magnetic field distribution is obtained by the charge model, so the eddy current inducted in the conductor is calculated. Then the damping force is obtained after the equivalent resistance and inductance of conductors are calculated. The formula of damping force is obtained to optimize damping structure of short-stroke DCLM. The accuracy of damping force model is proved by the experiment.

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.

Development of a New Passive-Active Magnetic Damper for Vibration Suppression

2005 ◽  
Vol 128 (3) ◽  
pp. 318-327 ◽  
Author(s):  
Henry A. Sodano ◽  
Daniel J. Inman ◽  
W. Keith Belvin
Keyword(s):  
Magnetic Field ◽  
Control System ◽  
Eddy Currents ◽  
Vibration Suppression ◽  
Internal Resistance ◽  
Viscous Force ◽  
Damping Force ◽  
Conductive Material ◽  
Damping Effect ◽  
Active Portion

Magnetic fields can be used to apply damping to a vibrating structure. Dampers of this type function through the eddy currents that are generated in a conductive material experiencing a time-changing magnetic field. The density of these currents is directly related to the velocity of the change in magnetic field. However, following the generation of these currents, the internal resistance of the conductor causes them to dissipate into heat. Because a portion of the moving conductor’s kinetic energy is used to generate the eddy currents, which are then dissipated, a damping effect occurs. This damping force can be described as a viscous force due to the dependence on the velocity of the conductor. In a previous study, a permanent magnet was fixed in a location such that the poling axis was perpendicular to the beam’s motion and the radial magnetic flux was used to passively suppress the beam’s vibration. Using this passive damping concept and the idea that the damping force is directly related to the velocity of the conductor, a new passive-active damping mechanism will be created. This new damper will function by allowing the position of the magnet to change relative to the beam and thus allow the net velocity between the two to be maximized and thus the damping force significantly increased. Using this concept, a model of both the passive and active portion of the system will be developed, allowing the beams response to be simulated. To verify the accuracy of this model, experiments will be performed that demonstrate both the accuracy of the model and the effectiveness of this passive-active control system for use in suppressing the transverse vibration of a structure.

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.

Modeling Eddy-Current Damping Force in Magnetic Levitation Systems With Conductors

2017 ◽  
Author(s):  
Mohammad Khodabakhsh ◽  
Mehran Ebrahimian ◽  
Bogdan Epureanu
Keyword(s):  
Permanent Magnet ◽  
Eddy Current ◽  
Eddy Currents ◽  
Magnetic Levitation ◽  
Analytical Models ◽  
Damping Force ◽  
Element Analysis ◽  
Wide Range ◽  
Eddy Current Damping ◽  
Damping Effects

An analytical method is used to develop a model to calculate steady-state eddy-current damping effects in two configurations of magnetic levitation (maglev) systems. The eddy-current based force (eddy-current force) is used for high precision positioning of a levitated permanent magnet in maglev systems. In these systems, the motion of the levitated permanent magnet and changes of the coil’s currents, generate eddy current in the conductors. The proposed analytical model is used to calculate both effects. A conductive cylindrical shell around the levitated object is implemented as a new technique to generate eddy currents in maglev systems. The model is also employed to obtain eddy-current damping effects in a system with a conductive plate beneath the levitated object. The analytical models match results from high fidelity finite element analysis (FEA) with acceptable accuracy in a wide range of operations. Advantages of the two configurations are discussed.

scholarly journals A fast forward solution with a boundary element method for eddy current nondestructive testing

2002 ◽  
Vol 15 (2) ◽  
pp. 205-216
Author(s):  
Hermann Uhlmann ◽  
Olaf Michelsson
Keyword(s):  
Magnetic Field ◽  
Boundary Element Method ◽  
Boundary Element ◽  
Eddy Current ◽  
Eddy Currents ◽  
Order Approximation ◽  
Approximation Schemes ◽  
Constant Field ◽  
The Magnetic Field ◽  
Element Method

Eddy current non-destructive testing is used to determine position and size of cracks or other defects in conducting materials. The presence of a crack normal to the excited eddy currents distorts the magnetic field; so for the identification of defects a very accurate and fast 3D-computation of the magnetic field is necessary. A computation scheme for 3D quasistatic electromagnetic fields by means of the Boundary Element Method is presented. Although the use of constant field approximations on boundary elements is the easiest way, it often provides an insufficient accuracy. This can be overcome by higher order approximation schemes. The numerical results are compared against some analytically solvable arrangements.

scholarly journals General 3D Analytical Method for Eddy-Current Coupling with Halbach Magnet Arrays Based on Magnetic Scalar Potential and H-Functions

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8458
Author(s):  
Xiaoquan Lu ◽  
Xinyi He ◽  
Ping Jin ◽  
Qifeng Huang ◽  
Shihai Yang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Analytical Method ◽  
Eddy Currents ◽  
Scalar Potential ◽  
Fourier Decomposition ◽  
Field Distributions ◽  
Current Coupling ◽  
Current Calculation ◽  
Laplacian Equations

Rapid and accurate eddy-current calculation is necessary to analyze eddy-current couplings (ECCs). This paper presents a general 3D analytical method for calculating the magnetic field distributions, eddy currents, and torques of ECCs with different Halbach magnet arrays. By using Fourier decomposition, the magnetization components of Halbach magnet arrays are determined. Then, with a group of H-formulations in the conductor region and Laplacian equations with magnetic scalar potential in the others, analytical magnetic field distributions are predicted and verified by 3D finite element models. Based on Ohm’s law for moving conductors, eddy-current distributions and torques are obtained at different speeds. Finally, the Halbach magnet arrays with different segments are optimized to enhance the fundamental amplitude and reduce the harmonic contents of air-gap flux densities. The proposed method shows its correctness and validation in analyzing and optimizing ECCs with Halbach magnet arrays.

A new type of damper combining eddy current damping with rack and gear

2020 ◽  
pp. 107754632093711
Author(s):  
Yafeng Li ◽  
Shouying Li ◽  
Jianzhong Wang ◽  
Zhengqing Chen
Keyword(s):  
Eddy Current ◽  
Permanent Magnets ◽  
Air Gap ◽  
Damping Coefficient ◽  
Apparent Mass ◽  
Damping Force ◽  
Equivalent Damping ◽  
Eddy Current Damping ◽  
New Type ◽  
Equivalent Damping Coefficient

A new type of damper combining eddy current damping with rack and gear, which can simultaneously export damping and inertial forces, is proposed. Eddy current damping with rack and gear is supposed to be installed between the building superstructure and foundation to mitigate the seismic response of the building. First, the concept of eddy current damping with rack and gear is introduced in detail and its apparent mass and equivalent damping coefficient are both theoretically investigated. Second, a prototype of eddy current damping with rack and gear is manufactured, and a series of tests on the prototype are carried out to verify its structural parameters. The experimental and theoretical results of the apparent mass of the prototype agree well with each other. The experimental result of the equivalent damping coefficient of the prototype is slightly lower than the numerical results obtained from COMSOL Multiphysics and its maximum relative differences are 11.3% and 13.6% for α = 0° and 45°, respectively. Third, detailed parametric studies on the damping force, including the effects of the thickness of the conductor plate, air gap, and number and location of permanent magnets, are conducted. The results show that the damping force keeps a linear relationship with velocity if it is lower than 0.15 m/s, and with the increase of the velocity, a strong nonlinear relationship between the damping force and the velocity is observed. The available maximum damping force can be increased by decreasing the thickness of the conductor plate and the air gap, increasing the number of permanent magnets. There is an optimal location about the permanent magnets for the available maximum damping force. In addition, the hysteretic curves of the eddy current damping with rack and gear obtained from the test indicate that the ability of energy dissipation is considerable.

The Simulation Study on Temperature Field Distribution of 220 kV Gas Insulated Switchgear

2021 ◽  
Vol 16 (5) ◽  
pp. 797-805
Author(s):  
Bao-Ming Gao ◽  
Zheng-Yu Li ◽  
Jin-Wen Gao ◽  
Hao Liang ◽  
Zhi Yan ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Distribution ◽  
Eddy Current ◽  
Temperature Rise ◽  
Heat Dissipation ◽  
Eddy Currents ◽  
Coupling Effect ◽  
Eddy Current Loss ◽  
Element Analysis ◽  
Current Loss

Under working conditions, the conductive rods in the GIS flow through the power frequency alternating current. Due to the coupling effect of the magnetic field and electric field between the metal aluminum shell and the conductive rod, induced eddy currents are generated in the metal shell of the GIS. The heat generated by the current heating effect of the GIS conductive rod and the eddy current loss of the metal casing will cause the temperature rise of GIS equipment. Due to the limited volume, the heat dissipation capacity of GIS is poor. Excessive temperature rise will accelerate the insulation aging of GIS equipment, and even damage its insulation, which will affect safe operation. In order to obtain the temperature change law of GIS, related influencing factors such as eddy current loss, skin effect, proximity effect, convective heat transfer of SF6 gas, and gravity of SF6 gas are comprehensively considered. The finite element analysis is used to research and discuss GIS magnetic field distribution, eddy current, temperature distribution and SF6 gas velocity. The initial value of the temperature of each part is set to 293.15 K (20 °C), and the temperature in the GIS is calculated to gradually decrease from the inside to the outside under the rated AC current of 3150 A. The temperature at the conductive rod position is the highest at 335.32 K, and the temperature at the housing position is the lowest at 294.65 K.

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