Operation of an Electromagnetic Eddy-Current Damper with a Supercritical Shaft

1994 ◽  
Vol 116 (4) ◽  
pp. 578-580 ◽  
Author(s):  
J. R. Frederick ◽  
M. S. Darlow
Keyword(s):  
Eddy Current ◽  
High Speed ◽  
Eddy Currents ◽  
Squeeze Film ◽  
Future Research ◽  
Rotating Shaft ◽  
Small Disk ◽  
Eddy Current Damper ◽  
Speed Stability

A basic problem inherent with the operation of supercritical shafting is the application of appropriate external damping, which is generally necessary to suppress nonsynchronous instabilities and limit the synchronous response of even a well-balanced shaft. Typically, coulomb or squeeze film-type dampers are used, in which case the damping properties tend to change with temperature, and the necessary contact results in additional torque loading and wear. An alternative damping method currently under investigation is the application of a noncontact electromagnetic damper that dissipates energy through induced eddy-currents generated in a small disk mounted to, and rotating with the shaft (Frederick, 1990). Research is underway on the design and development of a damper of this type that could eventually lend itself to active control applications. The objectives of this investigation are the initial design of a magnetic circuit, an appropriate d-c power supply, and the characterization of preliminary performance experiments on a composite shaft. Damper operation was evaluated during rotating shaft tests and compared to prior tests which involved the use of a permanent magnet eddy-current damper. This Note concerns some interesting results obtained from these preliminary tests. The damper worked well at low speeds, but some high-speed stability problems were encountered. Potential solutions to these problems as well as areas of future research are discussed.

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.

Dynamics of a Rotating System With a Nonlinear Eddy-Current Damper

1998 ◽  
Vol 120 (4) ◽  
pp. 848-853 ◽  
Author(s):  
Y. Kligerman ◽  
O. Gottlieb
Keyword(s):  
Nonlinear Dynamics ◽  
Eddy Current ◽  
Eddy Currents ◽  
Nonlinear Behavior ◽  
Forced Response ◽  
System Response ◽  
Rotating System ◽  
Restoring Force ◽  
Rotating Systems ◽  
Eddy Current Damper

We investigate the nonlinear dynamics and stability of a rotating system with an electromagnetic noncontact eddy-current damper. The damper is modeled by a thin nonmagnetic disk that is translating and rotating with a shaft in an air gap of a direct current electromagnet. The damper dissipates energy of the rotating system lateral vibration through induced eddy-currents. The dynamical system also includes a cubic restoring force representing nonlinear behavior of rubber o-rings supporting the shaft. The equilibrium state of the balanced rotating system with an eddy-current damper becomes unstable via a Hopf bifurcation and exact solutions for the limit cycle radius and frequency of the self-excited oscillation are obtained analytically. Forced vibration induced by the rotating system mass imbalance is also investigated analytically and numerically. System response includes periodic and quasiperiodic solutions. Stability of the periodic solutions obtained from the balanced self-excited motion and the imbalance forced response is analyzed by use of Floquet theory. This analysis enables an explanation of the nonlinear dynamics and stability phenomena documented for rotating systems controlled by electromagnetic eddy-current dampers.

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.

Dynamics of a Rotating System With a Nonlinear Eddy-Current Damper

1997 ◽  
Author(s):  
Yuri Kligerman ◽  
Oded Gottlieb
Keyword(s):  
Nonlinear Dynamics ◽  
Eddy Current ◽  
Eddy Currents ◽  
Nonlinear Behavior ◽  
Forced Response ◽  
System Response ◽  
Rotating System ◽  
Restoring Force ◽  
Rotating Systems ◽  
Eddy Current Damper

Abstract The investigation of nonlinear dynamics and stability of a rotating system with an electromagnetic non-contact eddy-current damper is carried out. The damper is modeled by a thin nonmagnetic disk that is translating and rotating with a shaft in an air gap of a direct current electromagnet. The damper dissipates energy of the rotating system lateral vibration through induced eddy-currents. The dynamical system also includes a cubic restoring force representing nonlinear behavior of rubber o-rings supporting the shaft. The equilibrium state of the balanced rotating system with an eddy-current damper becomes unstable via a Hopf bifurcation and exact solutions for the limit cycle radius and frequency of the self-excited oscillation are obtained analytically. Forced vibration induced by the rotating system mass imbalance is also investigated analytically and numerically. System response includes periodic and quasiperiodic solutions. Stability of the periodic solutions obtained from the balanced self-excited motion and the unbalance forced response is analyzed by use of Floquet theory. This analysis enables an explanation of the nonlinear dynamics and stability phenomena documented for rotating systems controlled by electromagnetic eddy-current dampers.

Self-Powered Eddy Current Damper for Rotordynamic Applications

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Mario Silvagni ◽  
Andrea Tonoli ◽  
Angelo Bonfitto
Keyword(s):  
Eddy Current ◽  
Rotating Shaft ◽  
Electric Generator ◽  
Three Phase ◽  
Rolling Element ◽  
Transformer Type ◽  
Eddy Current Damper ◽  
Self Powered ◽  
Fluid Dampers ◽  
Absence Of Power

The vibration control of rotors is often performed using elastomeric or fluid dampers together with rolling element or hydrodynamic type bearings. Electromagnetic dampers seem a valid alternative to conventional solutions and also to active magnetic bearings (AMBs) because their simpler architecture, size and, if of transformer type, also for the absence of power electronics, position sensors, and any fast feedback loop. However, transformer eddy current dampers require a constant voltage power supply than can be provided by an embedded generator to reduce cost and improve the reliability. The present paper proposes a self-powered damper to fulfill these requirements. A three-phase permanent magnet electric generator (connected to the rotating shaft) generates the required power for the damping device. The generator is connected to the damping circuit by means of tuned impedance and a three-phase rectifier.

Design of a vibration isolation system using eddy current damper

2013 ◽  
Vol 228 (4) ◽  
pp. 664-675 ◽  
Author(s):  
Partha Paul ◽  
Chetan Ingale ◽  
Bishakh Bhattacharya
Keyword(s):  
Eddy Current ◽  
Vibration Isolation ◽  
Eddy Currents ◽  
High Efficiency ◽  
Experimental Studies ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Analysis And Design ◽  
Passive Vibration Isolation ◽  
Eddy Current Damper

This article aims at modeling, analysis and design of a passive vibration isolation system using a magnetic damper with high efficiency and compactness. The experimental set-up was developed for a single degree-of-freedom vibration isolation system, where the damper consists of two elements: an outer stationary conducting tube made up of copper and a moving core made up of an array of three ring-shaped neodymium magnets of Nd–Fe–B alloy separated by four block cylinders made of mild steel that are fixed to a steel rod. The generation of eddy currents in the conductor and its resistance causes the mechanical vibration to dissipate heat energy. The vibration response of the system is obtained starting from a low-frequency range. The proposed magnetic damper achieves a maximum transmissibility value less than two for a natural frequency that is less than 10 Hz and the excitations at higher frequencies are successfully isolated. Numerical and experimental studies were carried out for a range of system parameters which show that isolators based on magnetic damping could be very effective for passive vibration isolation. Further, a theoretical model for an active isolation system is proposed in order to reduce the transmissibility at resonance. It is envisaged that the combined active–passive eddy current damper could be effectively used for vibration isolation.

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.

scholarly journals Modelling and Test of an Integrated Magnetic Spring-Eddy Current Damper for Space Applications

Actuators ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 8
Author(s):  
Efren Diez-Jimenez ◽  
Cristina Alén-Cordero ◽  
Roberto Alcover-Sánchez ◽  
Eduardo Corral-Abad
Keyword(s):  
Mechanical Properties ◽  
Eddy Current ◽  
Permanent Magnets ◽  
High Reliability ◽  
Magnetic Suspension ◽  
Space Applications ◽  
Magnetic Spring ◽  
Eddy Current Damper ◽  
Mechanical Suspension

We present the design, manufacturing, and dynamical characterization of a mechanical suspension made by a passive magnetic spring and an eddy current damper integrated into a single device. Three configurations with 2, 3, and 4 permanent magnets axially distributed with opposite polarizations are designed, simulated, manufactured, and tested. Stiffness of 2410, 2050, 2090 N/m and damping coefficient of 5.45, 10.52 and 17.25 Ns/m are measured for the 2-, 3-, and 4-magnets configurations, respectively. The magnetic suspension provides good mechanical properties combined with excellent cleanness and high reliability, which is very desirable in mechanical systems for space applications.

Precision Motion Control with Active Eddy Current Damper

2010 ◽  
Vol 447-448 ◽  
pp. 493-497
Author(s):  
Chek Sing Teo ◽  
Chea Jack Ong ◽  
C.J. Ho ◽  
S. Huang ◽  
K.K. Tan
Keyword(s):  
Eddy Current ◽  
Eddy Currents ◽  
Vibration Suppression ◽  
Linear Motor ◽  
Precision Motion Control ◽  
Damping Effect ◽  
Eddy Current Damper ◽  
Damper Design ◽  
Precision Motion ◽  
Conducting Sheet

This paper describes the design and proof of concept for an active eddy current damper which is integrated into a single-axis linear motor. Although developments on active eddy current damper are well documented, none has been implemented in a linear motor. The advantage of such a system is two-fold. Firstly, the relative motion between the magnets and the conducting sheet produces eddy currents resulting in an electromagnetic force opposing the direction of motion; which can be utilized to suppress vibrations. Secondly, it is possible to enhance the damping effect of the system; Due to environmental noise, it is normally not possible to increase the D coefficient in a PID controller as much as desirable. The damper is thus able to supplement this damping effect to improve settling time. Here, we will present the damper design as well as the preliminary experiment results for both vibration suppression and motion damping.

Improved Concept and Model of Eddy Current Damper

2005 ◽  
Vol 128 (3) ◽  
pp. 294-302 ◽  
Author(s):  
Henry A. Sodano ◽  
Jae-Sung Bae ◽  
Daniel J. Inman ◽  
W. Keith Belvin
Keyword(s):  
Magnetic Field ◽  
Theoretical Model ◽  
Eddy Current ◽  
Eddy Currents ◽  
Opposite Polarity ◽  
Image Method ◽  
Time Varying ◽  
Transverse Beam ◽  
Eddy Current Damper ◽  
Improved Model

When a conductive material experiences a time-varying magnetic field, eddy currents are generated in the conductor. These eddy currents circulate such that they generate a magnetic field of their own, however the field generated is of opposite polarity, causing a repulsive force. The time-varying magnetic field needed to produce such currents can be induced either by movement of the conductor in the field or by changing the strength or position of the source of the magnetic field. In the case of a dynamic system the conductor is moving relative to the magnetic source, thus generating eddy currents that will dissipate into heat due to the resistivity of the conductor. This process of the generation and dissipation of eddy current causes the system to function as a viscous damper. In a previous study, the concept and theoretical model was developed for one eddy current damping system that was shown to be effective in the suppression of transverse beam vibrations. The mathematical model developed to predict the amount of damping induced on the structure was shown to be accurate when the magnet was far from the beam but was less accurate for the case that the gap between the magnet and beam was small. In the present study, an improved theoretical model of the previously developed system will be formulated using the image method, thus allowing the eddy current density to be more accurately computed. In addition to the development of an improved model, an improved concept of the eddy current damper configuration is developed, modeled, and tested. The new damper configuration adds significantly more damping to the structure than the previously implemented design and has the capability to critically damp the beam’s first bending mode. The eddy current damper is a noncontacting system, thus allowing it to be easily applied and able to add significant damping to the structure without changing dynamic response. Furthermore, the previous model and the improved model will be applied to the new damper design and the enhanced accuracy of this new theoretical model will be proven.

Sign in / Sign up

Export Citation Format

Share Document