Geometric Effects on Eddy Current Bearing Performance

1989 ◽  
Vol 111 (2) ◽  
pp. 209-214 ◽  
Author(s):  
J. A. Tichy ◽  
K. A. Connor
Keyword(s):  
Eddy Current ◽  
Eddy Currents ◽  
Load Capacity ◽  
Complex Mixture ◽  
Journal Bearings ◽  
Magnetic Bearings ◽  
Repulsive Forces ◽  
The Magnetic Field ◽  
Geometric Effects ◽  
Current Journal

The properties of magnetic bearings, particularly those based on repulsive forces due to eddy currents, are determined by a complex mixture of electrical and mechanical length and time scales. A perturbation solution for the magnetic field structure based on careful ordering of these parameters has permitted the effects of realistic gap geometries to be analyzed. The load capacity of eddy current journal bearings is found to be somewhat larger than previously predicted in an earlier paper which used magnetic fields based on constant gap size. The present results may be of interest to those concerned with calculating eddy currents in conventional attractive magnetic bearings.

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 Design of eddy current brake for electric motorcycle braking system

2021 ◽  
Vol 12 (1) ◽  
pp. 41
Author(s):  
Mufti Reza Aulia Putra ◽  
Muhammad Nizam ◽  
Dominicus Danardono Dwi Prija Tjahjana
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Eddy Current ◽  
Eddy Currents ◽  
Motor Vehicles ◽  
Braking Performance ◽  
Braking System ◽  
Fem Method ◽  
The Magnetic Field ◽  
Aluminum Disk

Braking systems in motor vehicles generally use a braking system that utilizes friction. The braking performance will decrease caused by using friction rapidly. To overcome this, as an alternative, an electromagnetic braking system can be used by utilizing eddy currents, such as eddy current brakes (ECB). Eddy currents are generated when the rotor pass the magnetic field of the electromagnet. The research aim is to design an ECB system. The performance of the disk design will be determined in this study. The study is about the tendency of the ECB properties. The finite element (FEM) method is used by modeling ECB performance. The experimental results were used to validate the result. The test showed the results of braking using aluminum disk showed the best performance in 12.03 Nm. From these results, the combination of the disks is needed by an appropriate disk design.

Progress on electrodynamic passive magnetic bearings for rotor levitation

2013 ◽  
Vol 228 (10) ◽  
pp. 1829-1844 ◽  
Author(s):  
JG Detoni
Keyword(s):  
Magnetic Field ◽  
Relative Motion ◽  
Degrees Of Freedom ◽  
Eddy Currents ◽  
Industrial Applications ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Critical Issues ◽  
Repulsive Forces ◽  
Electrodynamic Suspension

Electrodynamic suspension exploits repulsive forces due to eddy currents to produce positive stiffness by passive means, without violating the Earnshaw stability criterion. Systems employing this principle to levitate a rotor radial and/or axial degrees of freedom are called electrodynamic bearings (EDBs). Since the eddy currents can be induced either by using alternating current supplied electromagnets or by the relative motion between a conductor and a constant magnetic field, the research on EDBs has developed many different configurations. The present paper reviews the literature on electrodynamic passive magnetic bearings to analyze the evolution of this technology toward completely passive, stable, rotor levitation, and to compare the EDBs performance with other common magnetic bearing technologies. Radial and axial EDB technologies are reviewed attempting to create an organized connection between the works and to discuss some critical issues that still preclude the use of EDBs in industrial applications.

Surface Roughness and Magnetic Effect of Magnetized Journal Bearings Lubricated with Ferrofluid

2015 ◽  
Vol 642 ◽  
pp. 242-247
Author(s):  
Tze Chi Hsu ◽  
Jing Hong Chen ◽  
Tsu Liang Chou ◽  
Hsiu Lu Chiang
Keyword(s):  
Magnetic Field ◽  
Surface Roughness ◽  
Load Capacity ◽  
Hydrodynamic Pressure ◽  
Critical Value ◽  
Journal Bearings ◽  
Diameter Ratio ◽  
Eccentricity Ratio ◽  
High Eccentricity ◽  
The Magnetic Field

This study investigated the combined influence of stochastic surface roughness patterns and a magnetic field produced by an infinitely long wire on the distribution of hydrodynamic pressure in journal bearings lubricated with ferrofluids. According to our results, the magnetic field can raise the dimensionless pressure, improve the dimensionless load capacity and reduce the modified friction coefficient, especially at high eccentricity ratio. However, these bearing Characteristics are also influenced by surface roughness pattern depend on the length to diameter ratio λ, and the critical value of λ equal to 0.6, 0.95 and 1.8 in this study.

An Eddy Current Phenomenon

1978 ◽  
Vol 15 (2) ◽  
pp. 125-129
Author(s):  
J. Greig ◽  
David Thompson
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Eddy Currents ◽  
Current Filament ◽  
Current Filaments ◽  
The Magnetic Field

An experiment which shows negligible reaction from eddy currents in iron on their inducing field is described. The observations are shown to agree with the extension of Searle's results for the magnetic field of a long current filament in iron to an aggregation of current filaments such as eddy currents.

scholarly journals Analysis and Experiment of Eddy Current Loss in Radial Magnetic Bearings with Solid Rotor

2018 ◽  
Vol 198 ◽  
pp. 04002 ◽  
Author(s):  
Zengyuan Yin ◽  
Yuanwen Cai ◽  
Weijie Wang ◽  
Yuan Ren
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Eddy Current Loss ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Fourier Series Expansion ◽  
Eddy Current Losses ◽  
Current Loss ◽  
Radial Magnetic Bearing ◽  
The Magnetic Field

In order to reduce power losses for the aerospace applications, this paper analyzes the eddy current losses produced by high-speed rotating solid rotor core magnetic bearings of magnetically suspended control & sensitive gyroscope (MSCSG). An analytical model of the eddy current loss of a solid rotor radial magnetic bearing (RMB) is presented. Considering the difference between NNNN and NSNS magnetic circuits of RMB, the magnetic field expressions of stator magnetic poles are listed. The magnetic field of stator poles is replaced by Fourier series expansion. According to the magnetic field distribution around the magnetic pole surface and the boundary conditions of the rotor surface, the mathematical expression of eddy current loss is obtained. The measurement method of rotational power loss in radial magnetic bearing is proposed, and the results of the theoretical analysis are verified by experiments in the prototype MSCSG. The experimental results show the correctness of calculation results. Eddy current loss models and test methods provide theoretical support for analyzing eddy current losses in solid rotors and reducing power consumption.

Analysis of an Eddy Current Journal Bearing

1988 ◽  
Vol 110 (2) ◽  
pp. 320-326 ◽  
Author(s):  
K. A. Connor ◽  
J. A. Tichy
Keyword(s):  
Eddy Current ◽  
Journal Bearing ◽  
Surface Current ◽  
Modern Technology ◽  
Transportation Systems ◽  
Necessary Condition ◽  
Clearance Ratio ◽  
Active Feedback ◽  
Repulsive Forces ◽  
Current Journal

Nearly all magnetic bearings which have found use in modern technology are based on the attractive force between a magnet and a magnetic material. A distinct disadvantage is that such devices are inherently unstable and require active feedback for operation. In the present study an eddy current bearing is analyzed which uses repulsive forces to levitate a rotor, as in proposed advanced rail transportation systems. The journal bearing is considered to be a series of one-dimensional pads wrapped around a shaft. Maxwell’s equations are solved for the equivalent Cartesian geometry pad and rotor. This system is modeled as a sinusoidally varying surface current backed with an infinitely permeable (magnetic) pad which is separated from a conductive nonmagnetic rotor by a free gap. The magnetic forces are found to vary inversely with gap size, a necessary condition for stability. The behavior of an eddy current journal bearing is calculated and compared to that of fluid film bearings. Load, “friction” (which may also serve as propulsion), and attitude angle are determined as a function of eccentricity ratio, a slip parameter, clearance ratio and a number of pads. The approximate results presented may serve as guidelines for development work and subsequent analysis.

Development of a New High Sensitive Eddy Current Sensor

2014 ◽  
Vol 792 ◽  
pp. 98-103 ◽  
Author(s):  
Hiroki Kikuchihara ◽  
Illiana Marinova ◽  
Yoshifuru Saito ◽  
Manabu Ohuchi ◽  
Hideo Mogi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Eddy Current ◽  
Eddy Currents ◽  
Impedance Sensing ◽  
Field Source ◽  
Current Path ◽  
Conducting Materials ◽  
2D And 3D ◽  
The Magnetic Field

Eddy current testing (ECT) is one of the most representative nondestructive testing methods for metallic materials, parts, structures and so on. Operating principle of ECT is based on two major properties of the magnetic field. One is that alternating magnetic field induces eddy current in conducting materials. Thereby, an input impedance of the magnetic field source, i.e., electric source, depends on the eddy current path. Second is that the magnetic field distribution depends not only on the exciting but also on the reactive magnetic fields caused by the eddy currents in targets. Former and latter are the impedance sensing and magnetic flux sensing types, respectively.This paper concerns with an optimization of a new magnetic flux sensing type sensor named coil. Exciting and sensing coils are composed of shape coil and a finite length solenoid coil wound on ferrite bar, respectively. Development of this coil fully depends on the 2D and 3D finite elements method modeling. According to the simulation results, we have worked out two types of coils. Practical experiments reflect the validity of both simulation and design aims, quite well. Thus, we have succeeded in developing coil having a higher sensibility compared with that of conventional one.

Determination of eddy current losses and hysteresis losses in magnetic circuits of electrical machines

2020 ◽  
pp. 54-58
Author(s):  
S. M. Plotnikov
Keyword(s):  
Eddy Current ◽  
Magnetization Reversal ◽  
Eddy Currents ◽  
Technical Problem ◽  
Electrical Machines ◽  
Eddy Current Losses ◽  
Hysteresis Losses ◽  
Magnetic Circuits ◽  
Core Losses ◽  
Reversal Frequency

The division of the total core losses in the electrical steel of the magnetic circuit into two components – losses dueto hysteresis and eddy currents – is a serious technical problem, the solution of which will effectively design and construct electrical machines with magnetic circuits having low magnetic losses. In this regard, an important parameter is the exponent α, with which the frequency of magnetization reversal is included in the total losses in steel. Theoretically, this indicator can take values from 1 to 2. Most authors take α equal to 1.3, which corresponds to the special case when the eddy current losses are three times higher than the hysteresis losses. In fact, for modern electrical steels, the opposite is true. To refine the index α, an attempt was made to separate the total core losses on the basis that the hysteresis component is proportional to the first degree of the magnetization reversal frequency, and the eddy current component is proportional to the second degree. In the article, the calculation formulas of these components are obtained, containing the values of the total losses measured in idling experiments at two different frequencies, and the ratio of these frequencies. It is shown that the rational frequency ratio is within 1.2. Presented the graphs and expressions to determine the exponent α depending on the measured no-load losses and the frequency of magnetization reversal.

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