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1887

Proceedings of the Institution of Electrical Engineers

Volume 124, Issue 11, November 1977

Volumes & issues:

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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  • p. 987 –992 (6)
    Quality-grading tests have been made to determine quantitatively the effect of video crosstalk in a visual-telephone 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 head-and-shoulders views of typical visual telephone users, two disturbing picture signals, one a head-and-shoulders view, and the other an electronically-generated 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 far-end and near-end crosstalk paths. For a subjective impairment of ¼ imp, this value is 33 dB for a head-and-shoulders 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.
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Discussion on “Method for simultaneous measurement of current and voltage on high-voltage lines using optical techniques”
Gamma-radiation 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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  • p. 995 –1000 (6)
    A novel gamma-ray 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.
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Calculation of Elmore-defined delay and rise times of RC ladder networks
Software system for studying Omega-phase 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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  • p. 1003 –1006 (4)
    With the full scale introduction of the Omega system of radio navigation, which has a world-wide 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.
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Summery. Variation of E-layer 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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  • p. 1007 –1008 (2)
    Ionospheric f0E 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 12-month average is independent of the latitude of the station. The uncertainty in the relations is mainly due to inconsistency between solar-cycle variations of f0E at different stations, butR appears less reliable than the other two parameters.
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Technique for calculating the radiation and scattering characteristics of antennas mounted on a finite ground plane
  • Author(s): P. Parhami ; Y. Rahmat-Samii ; 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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  • p. 1009 –1016 (8)
    The problem of an antenna mounted on a conducting body is formulated by using a modification of the isolated thin-wire 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 finite-difference technique, which has previously been successfully applied to the thin-wire junction problem. A user-oriented Fortran program is developed, and extensive numerical results are reported.
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Novel analytic technique for obtaining the spectrum associated with piecewise-linear frequency modulation
Frequency bandwidth of modified goubau line
Predetermination of current and torque requirements of an induction-motor-driven steel-bar 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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  • p. 1019 –1025 (7)
    A mathematical model is developed for a complete open-train steel-bar rolling-mill drive. It is used in the prediction of the current and torque requirements of the induction-motor 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 plastic-rigid materials is summarised.The validity of the model is checked by comparing results of a computer study with results taken from full-scale tests on a multistand rolling mill. Results showing the conditions that arise following the application of steel billets to the mill are presented.
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Comparison of alternative formulations of 3-dimensional magnetic-field and eddy-current 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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  • p. 1026 –1034 (9)
    The numerical calculation of 3-dimensional 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 vector-potential 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 vector-potential 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 magnetic-and electric-interface conditions.
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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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  • p. 1035 –1046 (12)
    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 variable-gap 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.
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General formulation for dynamic studies in power systems including static convertors
  • Author(s): J. Arrillaga ; H.J. Al-Khashali ; J.G. Campos-Barros
  • 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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  • p. 1047 –1052 (6)
    The presence of static convertors involves a power system in frequent waveform-dependent topological changes. A general model is described in this paper to analyse the dynamic interaction between convertors and power systems. An efficient state-space 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 power-system operation.
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Form of circle diagram for the linear induction motor
Computer-aided steady-state and transient solutions of field problems in induction devices
IEE Mersey & N. Wales Centre: Chairman's address. Manweb distribution 1950–2000
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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  • p. 1064 –1072 (9)
    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 longer-term 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 eddy-current 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.
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Calculation of current distribution and optimum dimensions of foil-wound air-cored reactors
  • Author(s): M.M. El-Missiry
  • 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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  • p. 1073 –1077 (5)
    An accurate and straightforward method is given for calculating the current distribution and impedance of foil-wound air-cored 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. Foil-wound 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.
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Analysis of rotor bar currents as a means of evaluating torque produced in a squirrel-cage induction motor
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. 1079 –1082 (4)
    The recent contribution by Edwards to the stability analysis of multipass processes using the familiar inverse-Nyquist method is discussed using the techniques of functional analysis. It is noted that the modelling procedure suggested by Edwards neglects the finite pass-length 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, time-invariant systems indicates that previous results are highly pessimistic. The anomaly is explained in terms of a defined notion of stability along the pass.
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1st-order-type 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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  • p. 1083 –1088 (6)
    It is well known in classical feedback control that many high-order linear time-invariant systems can be approximated, for the purpose of feedback design, by a low-order state-space model due to the presence of approximately cancelling poles and zeros in the system-transfer function. The paper presents an equivalent technique in the case of a multivariable system described by a strictly proper m × m, minimum-phase and invertible transfer-function matrix G(s) by the application of the contraction-mapping theorem. It is shown that, in many cases of practical interest, a multivariable 1st-order-type model is adequate for the purpose of control-system design, and that such a model can be determined directly from transient response data or, equivalently, by the analysis of the high- and low-frequency characteristics of the system. The application of the technique is illustrated by the analysis of a high-order binary-distillation-column model and the dynamics of a counter-flow heat exchanger.
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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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  • p. 1089 –1097 (9)
    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 energy-based 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 surface-integral 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.
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Analytical method of calculating the electromagnetic field and power losses in ferromagnetic halfspace, taking into account saturation and hysteresis
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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  • p. 1105 –1110 (6)
    An account is given of the relativistic component-field 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.
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Numerical methods in conformal transformation

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