scholarly journals III. Eddy-current losses in cylindrical conductors, with special applications to the alternating current resistances of short coils

1922 ◽  
Vol 222 (594-604) ◽  
pp. 57-100 ◽  
Keyword(s):  
Eddy Current ◽  
Eddy Currents ◽  
Alternating Current ◽  
Considerable Proportion ◽  
General Effect ◽  
Eddy Current Losses ◽  
Direct Current Resistance ◽  
Set Up ◽  
Cylindrical Conductors ◽  
Current Resistance

It is well-known that a considerable proportion of the effective resistance of inductive coils when used at radio frequencies is caused by the eddy-currents set up in the wires of the coils by the alternating magnetic field in which they are situated, and that in extreme cases the alternating current resistance may amount to more than one hundred times the direct current resistance. It is therefore important to have reliable formulæ for the eddy-current resistance of such coils in order to determine the conditions which will reduce the eddy-current losses to a minimum. The simplest case, that of a long straight cylindrical wire under the action of its own current, has been treated by Kelvin, Rayleigh, Heaviside, and others. The general effect is known as the “skin effect,” because the current tends to concentrate more and more upon the skin of the conductor as the frequency increases.

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.

Formulation for Stress Intensity Factors and J-Integral Calculation by Eddy Current Testing

2015 ◽  
Vol 660 ◽  
pp. 225-230 ◽  
Author(s):  
Salaheddine Harzallah ◽  
Mohamed Chabaat ◽  
Sekoura Benissad
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Eddy Current ◽  
Eddy Currents ◽  
J Integral ◽  
Intensity Factors ◽  
Magnetic Vector ◽  
Current Testing ◽  
Set Up

In this paper, we present a method for computing the Stress Intensity Factor (SIF) and J-Integral, by measuring and testing related Eddy currents. In the process, we provide a magnetic vector based formulations for the theoretical set up. Furthermore, we provide relevant applications having theory consistent results.

3D Eddy Current Testing by FEM for Detection of Crack’s in Materials

2016 ◽  
Vol 703 ◽  
pp. 349-353 ◽  
Author(s):  
Kahina Chabane ◽  
Salaheddine Harzallah ◽  
Mohamed Chabaat
Keyword(s):  
Eddy Current ◽  
Eddy Currents ◽  
Numerical Approach ◽  
Governing Equations ◽  
Finite Element Discretization ◽  
Magnetic Vector ◽  
Element Discretization ◽  
Current Testing ◽  
Micro Cracks ◽  
Set Up

In this paper, we present a nondestructive Testing by sensor Eddy current is used as a tool to control cracks and micro-cracks in materials. A new method for computing by measuring and testing related 3D Eddy currents is considered. In the process, a Potential Magnetic Vector is provided on the basis of formulations taken from the theoretical set up. Thus, results of relevant applications are obtained to check the theory consistency. A simulation by a numerical approach using Finite element discretization of 3-D Eddy Current governing equations is employed to detect cracks and damaged zones in materials and eventually to study their propagation.

Comparison of Electrical Resistance and Impedance Measurements in Wood in Progressive Stages of Discoloration and Decay

1973 ◽  
Vol 3 (4) ◽  
pp. 593-595 ◽  
Author(s):  
Terry A. Tattar ◽  
George C. Saufley
Keyword(s):  
Direct Current ◽  
Electrical Resistance ◽  
Alternating Current ◽  
Pulsed Current ◽  
Impedance Measurements ◽  
Direct Current Resistance ◽  
Current Resistance

Direct current resistance and alternating current impedance were used to detect and quantify wood in progressive stages of discoloration and decay in living trees. Results were comparable to those obtained with pulsed current under similar conditions.

Eddy currents in thin circular cylinders of uniform conductivity, due to periodically changing magnetic fields, in two dimensions

1927 ◽  
Vol 23 (8) ◽  
pp. 901-906 ◽  
Author(s):  
F. W. Carter
Keyword(s):  
Eddy Current ◽  
Eddy Currents ◽  
Two Dimensions ◽  
Circular Cylinders ◽  
Two Dimensional ◽  
Total Field ◽  
Current Field ◽  
Conducting Material ◽  
Eddy Current Losses ◽  
Three Phase

The paper deals with the eddy currents in thin circular cylinders of uniform conducting material, due to periodic currents in conductors lying parallel to the axis of the cylinder, or to the rotation of the cylinder in a two-dimensional field of force. The first of these problems was discussed by Mr M. B. Field in a paper entitled “Eddy current losses in three-phase cable sheaths,” read before the British Association at their Cambridge meeting in 1904. The solution proposed, however, although probably sufficient for the object, is mathematically defective, in that the field due to the current carried by the cable is assumed as the total field, the effect of the eddy-current field on the eddy currents themselves being left out of account.

scholarly journals Increasing the required slip range of wound induction generator in wind power systems

2020 ◽  
Vol 9 (2) ◽  
pp. 436-442
Author(s):  
Ali Dalabeeh ◽  
Al-Mofleh Anwar ◽  
Tariq M. Younes ◽  
Ayman Al-Rawashdeh ◽  
Ayman Hindi
Keyword(s):  
Power Systems ◽  
Wind Turbine ◽  
Eddy Current ◽  
Power Flow ◽  
Eddy Currents ◽  
Reactive Power ◽  
Induction Generator ◽  
Material Loss ◽  
Eddy Current Losses ◽  
Wound Induction

Eddy currents losses in the rotor in high power generators do not allow operators, under high values of slip, to regulate voltage and control of reactive power flow. The paper presents a method that can accurately estimate the eddy current losses in electric machines with a less complicated procedure. The suggested method allows researchers to analyze and reduce the losses, and consequently, to improve the wind turbine induction generators efficiencies. The given approach, based on the conventional electric machine theory and the parameters supplied by the manufacturers, predicts the eddy current losses theoretically without the need of the measured material loss data or BH curve. Increasing the range of slip variation of induction motor can be achieved by using a rotor of two layers in the radial direction with different parameters. The first layer is a laminated layer of height (h), and the second is a solid (the rotor yoke). The computation of eddy current losses is useful to change the design of the machine to minimize the losses. This paper presents a detailed modeling of the effect parameters on the eddy current losses in wind turbine induction generator.

AC losses of Roebel and CORC® cables at higher AC magnetic fields and Ramp Rates

2021 ◽  
Author(s):  
Mike D Sumption ◽  
John Murphy ◽  
Timothy J Haugan ◽  
Milan Majoros ◽  
Danko C van der Laan ◽  
...  
Keyword(s):  
Eddy Current ◽  
Eddy Currents ◽  
Flux Creep ◽  
Ac Losses ◽  
Radial Magnetic Field ◽  
Eddy Current Losses ◽  
Preparation Conditions ◽  
Sinusoidal Waveform ◽  
Helical Geometry ◽  
The Individual

Abstract We have measured ReBCO coated conductor-based CORC® and Roebel cables at 77 K in a Spinning Magnet Calorimeter which subjected the tapes in the samples to a radial magnetic field of 566 mT (peak) at frequencies up to 120 Hz (272 T/s, cyclic average) with an approximately sinusoidal waveform. The samples were oriented such that the field applied to the tapes within the cables was entirely radial, simplifying subsequent analysis. An expression for loss which included hysteretic, flux creep, and eddy current losses was fit to both the CORC® and the Roebel cables. This expression allowed easy comparison of the relative influence of eddy currents and flux creep (or power-law behavior) effects. The loss of both the CORC® and Roebel cables measured here were seen to be essentially the sum of the hysteretic loss, flux creep effects, and the normal metal eddy current losses of the individual tapes. The losses of these cables were measured at high B*dB/dt with no coupling current loss observed under the present preparation conditions. The influence of flux creep effects on loss were not negligible. The losses of the CORC® cable per meter of tape were seen to be reduced from the case of a flat tape because of the helical geometry of the tapes.

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