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Volume 124
Issue 11
Proceedings of the Institution of Electrical Engineers
Volume 124, Issue 11, November 1977
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Volume 124, Issue 11
November 1977
Subjective quality of visual telephone pictures impaired by video crosstalk
 Author(s): J.R. Taylor ; E.J.W. Bragg ; J.M. Corbett
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 987 –992
 DOI: 10.1049/piee.1977.0201
 Type: Article
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Qualitygrading tests have been made to determine quantitatively the effect of video crosstalk in a visualtelephone system with a scanning standard of 319 lines/picture, 50 fields/s and a nominal bandwidth of 1 MHz. The wanted and the disturbing signals were of types likely to be encountered in the local line network and were in analogue form. Although the wanted pictures were headandshoulders views of typical visual telephone users, two disturbing picture signals, one a headandshoulders view, and the other an electronicallygenerated caption, were used to represent the extremes of the probable range of subjective impairments. Three crosstalk paths were investigated, representing far end, near end and flat or undistorted crosstalk. By defining the crosstalk path at a frequency of 400 kHz, a single value of effective crosstalk attenuation, corresponding to a particular level of subjective impairment and a particular type of disturbing signal, is applicable for both farend and nearend crosstalk paths. For a subjective impairment of ¼ imp, this value is 33 dB for a headandshoulders disturbing signal and 40.5 dB for a caption disturbing signal. The corresponding values of signal/crosstalk ratio for flat crosstalk are 42 dB and 43.4 dB.
Discussion on “Method for simultaneous measurement of current and voltage on highvoltage lines using optical techniques”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 992 –994
 DOI: 10.1049/piee.1977.0202
 Type: Article
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Gammaradiation imaging system based on the Compton effect
 Author(s): D.B. Everett ; J.S. Fleming ; R.W. Todd ; J.M. Nightingale
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 995 –1000
 DOI: 10.1049/piee.1977.0203
 Type: Article
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A novel gammaray camera is proposed that is based on the Compton effect. The basis of the device is a segmented semiconductor detector which is able to locate successive interaction points in multicollision trajectories and the associated energy losses. In this way, conic section can be computed on an image plane for each emission from a point source in the object. An overall image can be constructed by summation of the individual ellipses. The effect of measurement errors is investigated theoretically and by simulation, and leads to favourable estimates for the resolution and sensitivity of the camera. The question of image processing to improve performance is briefly discussed.
Calculation of Elmoredefined delay and rise times of RC ladder networks
 Author(s): S.C. Dutta Roy
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1001 –1002
 DOI: 10.1049/piee.1977.0204
 Type: Article
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Closedform formulas are derived for the Elmoredefined delay and rise times of uniform as well as geometrically tapered RC ladder networks. These would be useful in assessing and comparing such networks in respect of their time domain performance.
Software system for studying Omegaphase data and fix accuracy on a small computer
 Author(s): D.J. Brain and R.C.V. Macario
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1003 –1006
 DOI: 10.1049/piee.1977.0205
 Type: Article
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With the full scale introduction of the Omega system of radio navigation, which has a worldwide capability, there is considerable interest in the assessment of positional fix accuracy at various fixed sites and monitoring stations. This is because Omega necessarily suffers from diurnal and seasonal variations. A software system, based on a standard minicomputer, is described. The system has the capability of carrying out positional fix assessment. Operation of the program is illustrated with the aid of actual Omega line of position (l.o.p.) data on two frequencies.
Summery. Variation of Elayer critical frequency with solar activity
 Author(s): S.S. Kouris
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1007 –1008
 DOI: 10.1049/piee.1977.0206
 Type: Article
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Ionospheric f_{0}E data over one or, where available, two solar cycles from 47 stations all over the world are correlated with the corresponding data of each of the three solar indices, the Zürich relative sunspot number R, the solar radio noise flux Φ at 10.7 cm and the ionospheric index of solar activity IF2, and numerical expressions are derived. There is no difference in the degree of correlation between the variates of each of the above expressions at the 5% level. At each station, the monthly values of the sensitivity to solar activity changes are independent of season and their 12month average is independent of the latitude of the station. The uncertainty in the relations is mainly due to inconsistency between solarcycle variations of f_{0}E at different stations, butR appears less reliable than the other two parameters.
Technique for calculating the radiation and scattering characteristics of antennas mounted on a finite ground plane
 Author(s): P. Parhami ; Y. RahmatSamii ; R. Mittra
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1009 –1016
 DOI: 10.1049/piee.1977.0207
 Type: Article
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The problem of an antenna mounted on a conducting body is formulated by using a modification of the isolated thinwire kernel with the numerical Green's function for the body. This formulation is then employed for the investigation of the problem of a monopole antenna over a finite ground plane. The numerical Green's function for the plate is obtained by applying the finitedifference technique, which has previously been successfully applied to the thinwire junction problem. A useroriented Fortran program is developed, and extensive numerical results are reported.
Novel analytic technique for obtaining the spectrum associated with piecewiselinear frequency modulation
 Author(s): A.S. Gladwin ; A.G.J. Holt ; G. Salkeld
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, page: 1016 –1016
 DOI: 10.1049/piee.1977.0208
 Type: Article
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Frequency bandwidth of modified goubau line
 Author(s): T.C.K. Rao and M.A.K. Hamid
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1017 –1018
 DOI: 10.1049/piee.1977.0209
 Type: Article
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p.
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Predetermination of current and torque requirements of an inductionmotordriven steelbar rolling mill
 Author(s): K.J. Binns ; J.R. Smith ; G.W. Buckley ; M. Lewis
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1019 –1025
 DOI: 10.1049/piee.1977.0210
 Type: Article
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A mathematical model is developed for a complete opentrain steelbar rollingmill drive. It is used in the prediction of the current and torque requirements of the inductionmotor drive, and it takes account of nonlinearities in the motor and mechanical coupling. The method of determining the mechanical parameters and the calculation of roll torque of plasticrigid materials is summarised.The validity of the model is checked by comparing results of a computer study with results taken from fullscale tests on a multistand rolling mill. Results showing the conditions that arise following the application of steel billets to the mill are presented.
Comparison of alternative formulations of 3dimensional magneticfield and eddycurrent problems at power frequencies
 Author(s): C.J. Carpenter
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1026 –1034
 DOI: 10.1049/piee.1977.0211
 Type: Article
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The numerical calculation of 3dimensional eddy currents is complicated by the need to use vector functions to describe the interlinked flux and current distributions. The three vector components are coupled, particularly by the conditions imposed by the copper and iron surfaces, and by other changes in material properties. The range of choice of magnetic and electric vector potentials is examined, including the ξ and H vectors as particular examples, and it is shown that the problem formulation is greatly affected by the choice of gauge, or vectorpotential divergence. This introduces scalar potentials which can be used in various ways. They control the coupling conditions between the vector components. One advantage of an electric vector potential, or generalised H, formulation is that the gauge can be chosen so that the vector is zero outside the conductors, and is replaced by a scalar. Magnetic vectorpotential formulations are generally less attractive, both because the vector has to be computed throughout the region of interest and because of the greater complexity of the magneticand electricinterface conditions.
Machines using rectified oscillatory motion
 Author(s): D.E. Hesmondhalgh and D. Tipping
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1035 –1046
 DOI: 10.1049/piee.1977.0212
 Type: Article
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Since the size of an electromagnetic machine specifies the torque, any further increase in torque for a given volume is achieved conventionally by a gearbox. The paper considers the implications of attaching a mechanical system consisting of a ratchet and resiliences to an oscillating actuator with a view first to exploiting the magnetic attraction force and secondly to obtaining a torque amplification by mechanical tuning. Both variablegap and conventional reluctance actuators are considered, and the characteristics of prototype machines are explained in terms of the equations of motion. A consideration of the ‘perfect ratchet’ is included, and design criteria presented which permit imperfect ratchets to be used to the best advantage.
General formulation for dynamic studies in power systems including static convertors
 Author(s): J. Arrillaga ; H.J. AlKhashali ; J.G. CamposBarros
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1047 –1052
 DOI: 10.1049/piee.1977.0213
 Type: Article
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The presence of static convertors involves a power system in frequent waveformdependent topological changes. A general model is described in this paper to analyse the dynamic interaction between convertors and power systems. An efficient statespace formulation is used, with isolation of the nodal equations affected by the variable topology. The degree of system representation accepted by the model is optional, but detailed representation is recommended for the convertor and a.c. related plant components, such as convertor transformers, filters and synchronous machines. The versatility of the model is illustrated by typical cases of normal and disturbed powersystem operation.
Form of circle diagram for the linear induction motor
 Author(s): E.M. Freeman and D.A. Lowther
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1053 –1056
 DOI: 10.1049/piee.1977.0214
 Type: Article
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A circle diagram is described for an idealised linear induction motor operating under constantcurrent conditions, with an ironbacked or airbacked conductingsheet rotor. The diagram yields a great deal of information about the performance of the machine, including normal force. Simplified expressions are derived relating complex input power, thrust and normal force. The theory is compared with the experimental results obtained from staticimpedance tests on a linear induction motor.
Computeraided steadystate and transient solutions of field problems in induction devices
 Author(s): E.M. Freeman
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1057 –1061
 DOI: 10.1049/piee.1977.0215
 Type: Article
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The paper describes a method for solving steadystate and transient electromagneticfield problems in certain multiregion induction devices, which uses only a very small amount of analysis. In general, the device is modelled by means of a nonuniform transmission line consisting of a large number of Tcircuits in cascade. Circuitanalysis computer packages can be used to solve for the circuit quantities, and hence the field quantities, at all nodes in the line. Neither higher transcendental functions nor operational methods are required.
IEE Mersey & N. Wales Centre: Chairman's address. Manweb distribution 1950–2000
 Author(s): J. Fisher
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1061 –1063
 DOI: 10.1049/piee.1977.0216
 Type: Article
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Heating in transformer cores due to radial leakage flux. Part 1: Experimental models and test results
 Author(s): R.F. Hemmings and G.D. Wale
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1064 –1072
 DOI: 10.1049/piee.1977.0217
 Type: Article
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The heating effects of radial fluxbecome increasingly important in the design of large power transformers, both because of the higher flux densities generally involved and larger dimensions of components affected, particularly the core clamping structure. This paper describes two series of models constructed to study the heating of transformers cores and core clamping structures under the influence of radial leakage flux from the windings. The first series of models was designed to obtain urgently needed design information on the temperatures to be expected in various practical geometries, and their longerterm effect on the insulating materials used in their construction, while the second series was used to allow a more detailed study of flux penetration and eddycurrent effects to be made. Formulas for the calculation of the losses and resultant temperature rises are derived and compared with measurements made both on the models and on transformers. The significance of the results for the design, testing and operation of transformers is discussed.
Calculation of current distribution and optimum dimensions of foilwound aircored reactors
 Author(s): M.M. ElMissiry
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1073 –1077
 DOI: 10.1049/piee.1977.0218
 Type: Article
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An accurate and straightforward method is given for calculating the current distribution and impedance of foilwound aircored reactors. It is applicable to coils of all sizes, including thin flat coils and long solenoids. Measurements of impedance show good correlation with calculated results. The effect of coil dimensions on the nonuniformity of current distribution is summarised in a set of curves in dimensionless form. Foilwound reactors are subjected to an optimisation study based on size, weight and electrical parameters. The new optimised forms which give maximum quality factor, calculated on the basis of nonuniform distribution of current, satisfying various requirements are given, in addition to the results of optimisation for minimum weight.
Analysis of rotor bar currents as a means of evaluating torque produced in a squirrelcage induction motor
 Author(s): C.F. Landy
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, page: 1078 –1078
 DOI: 10.1049/piee.1977.0219
 Type: Article
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Stability of linear multipass processes
 Author(s): D.H. Owens
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1079 –1082
 DOI: 10.1049/piee.1977.0220
 Type: Article
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p.
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The recent contribution by Edwards to the stability analysis of multipass processes using the familiar inverseNyquist method is discussed using the techniques of functional analysis. It is noted that the modelling procedure suggested by Edwards neglects the finite passlength nature of the processes and takes no account of the initial conditions for each pass. A natural and physically meaningful definition of multipass stability is proposed and characterised by conditions on the system operator. Application of the results to a cogging process and a class of linear, timeinvariant systems indicates that previous results are highly pessimistic. The anomaly is explained in terms of a defined notion of stability along the pass.
1stordertype models for multivariable process control
 Author(s): J.B. Edwards and D.H. Owens
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1083 –1088
 DOI: 10.1049/piee.1977.0221
 Type: Article
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It is well known in classical feedback control that many highorder linear timeinvariant systems can be approximated, for the purpose of feedback design, by a loworder statespace model due to the presence of approximately cancelling poles and zeros in the systemtransfer function. The paper presents an equivalent technique in the case of a multivariable system described by a strictly proper m × m, minimumphase and invertible transferfunction matrix G(s) by the application of the contractionmapping theorem. It is shown that, in many cases of practical interest, a multivariable 1stordertype model is adequate for the purpose of controlsystem design, and that such a model can be determined directly from transient response data or, equivalently, by the analysis of the high and lowfrequency characteristics of the system. The application of the technique is illustrated by the analysis of a highorder binarydistillationcolumn model and the dynamics of a counterflow heat exchanger.
Ferrofluid hydrostatics according to classical and recent theories of the stresses
 Author(s): J.V. Byrne
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1089 –1097
 DOI: 10.1049/piee.1977.0222
 Type: Article
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The hydrostatics of soft polarisable liquids is examined in the context of four ‘classical’ theories of the stresses in fluids, and of recent theoretical work which has resolved the controversy surrounding those theories. The classical stress systems predict various different internal pressures and magnetostrictive density changes, and only the stress system, based on energy, correctly gives the density change. The energybased stresses proposed by Gans in 1904 generalise for nonlinear fluids the stress system of Helmholtz. All the stress systems predict the same surface variation of the pressure to contain a liquid, and they lead to a common surfaceintegral method useful for computing force on saturable iron bodies. The modern theories are represented, for equilibrium conditions, by a single and unique stress system which gives no information on internal forces. The meaning of the various ‘pressures’ found in the recent literature is discussed, and the role of density, rather than pressure, as the predictable mechanical variable inside a liquid is illustrated by a thought experiment.
Analytical method of calculating the electromagnetic field and power losses in ferromagnetic halfspace, taking into account saturation and hysteresis
 Author(s): J.F. Gieras
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1098 –1104
 DOI: 10.1049/piee.1977.0223
 Type: Article
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The steadystate solution of electromagneticfield problems in ferromagnetic materials is given. The effects of magnetic saturation and hysteresis are included. The solution is based on the differential diffusion equation assuming variable complex magnetic permeability. A precise formula is given to calculate the total power losses due to eddy currents and hysteresis. Computed curves, together with measured curves, are given for active and reactive losses in mild steel. Good agreement is obtained between measured and computed values.
Electromagnetic induction in magnetic rod moving with high velocity
 Author(s): E.G. Cullwick and E.G. Cullwick
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, p. 1105 –1110
 DOI: 10.1049/piee.1977.0224
 Type: Article
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An account is given of the relativistic componentfield electromagnetic theory of moving bodies, which extends orthodox relativity theory by recognising sources of the field, and it is shown to have advantages over orthodox theory in aiding physical comprehension. It is then applied to the determination of the electromagnetic field in a cylindrical rod of nonretentive ferromagnetic material, which can be either a conductor or a dielectric, in motion with high velocity through crossed fields. Particular cases investigated include the electromotive force induced in the rod by its motion through a magnetic field, it being confirmed that this is independent of the relative permeability, and the magnetisation of the rod by its motion through an electrostatic field. Expressions for the polarisation and magnetisation of the moving rod are also obtained. All the results are considerably simplified if the velocity of the rod is small compared with the velocity of light. For low velocities the theory can be presented in simple terms without reference to the theory of relativity, and for this reason, and also because of its physical basis, it is considered to have considerable advantages.
Numerical methods in conformal transformation
 Author(s): A. Nicolaide
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 11, page: 1110 –1110
 DOI: 10.1049/piee.1977.0225
 Type: Article
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