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Welton, United Kingdom

Raven M.S.,28 The Crayke
Acta Technica CSAV (Ceskoslovensk Akademie Ved) | Year: 2015

Experimental measurements of the low frequency skin effect and internal inductance are given for a number of copper wires with different diameters and various linear solid cylindrical conductors including rods of copper, aluminium and brass. The measurements were compared with reference resistors, inductors and capacitors. The results obtained compared well with tests using a precision LCR meter at three spot frequencies and measurements using A.F. and R.F. impedance bridges over a range of frequencies. The final results were compared with theoretical analysis using Bessel functions that revealed the detection of the internal inductance of rods and wires which are several orders less than the external inductance. Deviations of the measured resistance exceeding the theoretical power law frequency dependance are discussed in terms of errors in the measurement techniques, resonance, transmission line reflections, radiation resistance and proximity effects. © 2015 Institute of Thermomechanics AS CR, v.v.i. Source


Brandao Faria J.A.,University of Lisbon | Raven M.S.,28 The Crayke
Progress In Electromagnetics Research M | Year: 2013

Maxwell equations can be used to formulate an analytical full time-domain theory of skin effect phenomena in circular cylindrical conductors without any detour into the frequency domain. The paper shows how this can be done and concomitantly provides the means to determine the time-varying per unit length voltage drop along the conductor from a given time-varying conductor current. The developed relationship between voltage and current is not very complicated and led the authors to examine the reasons why it has never been utilized in transient analysis, nor given special emphasis in the literature. Those reasons are thoroughly examined and the conclusion is that the conditions required for the application of a purely time-domain skin effect theory are very restrictive. Source


Raven M.S.,28 The Crayke
Acta Technica CSAV (Ceskoslovensk Akademie Ved) | Year: 2014

The vector potential method is used to solve the problem of transient conduction and skin effect in cylindrical conductors. Several time dependent current sources are analyzed including linear, quadratic and exponential. The stability factor is determined and the results for each case are presented. A simple method of measuring the skin effect using a digital multimeter is suggested. © 2014 Institute of Thermomechanics AS CR, v.v.i. Source


Raven M.S.,28 The Crayke
Acta Technica CSAV (Ceskoslovensk Akademie Ved) | Year: 2014

A technique is described for measuring impedance with frequency which uses a modified gain-phase meter. This employs novel software routines to extract the complex components of the impedance from the signal amplitude and phase. The paper presents an analysis of the technique followed by details of the de-embedding procedure. A separate alternative circuit analysis is presented for the measurement of capacitive impedance. The results of the experimental measurements show that the technique is sufficiently sensitive to measure the skin effect in a short copper rod at audio frequencies to about 10 MHz. These results are found to compare well with theoretical analysis using Bessel functions including the possible detection of the internal inductance of the rod which is significantly less than the external inductance. © 2014 Institute of Thermomechanics AS CR, v.v.i. Source


Raven M.S.,28 The Crayke
Acta Technica CSAV (Ceskoslovensk Akademie Ved) | Year: 2013

Maxwell's original vector potential analysis of time dependent current flow in a conducting wire is analyzed in detail and the results are compared with the better known analysis using Bessel functions. A normalized impedance is derived in terms of a dimensionless parameter proportional to the ratio of the conductor radius to skin depth. We also obtain general power series summations for the sinusoidal case obtaining equations for the coefficients in the infinite series, examine the stability of the series and find that if the skin depth decreases to less than 40 % of the wire radius, the series diverge sharply. © 2013 Institute of Thermomechanics AS CR, v.v.i. Source

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