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1887

Proceedings of the Institution of Electrical Engineers

Volume 124, Issue 12, December 1977

Volumes & issues:

Volume 124, Issue 12

December 1977

Evaluation of beam-scanning dual-reflector antennas
Some resonance effects in scattering of microwaves by hydrometeors
Computer-program description. Computer-program system for evaluating partial and total antenna directivities from measured data. Computer-program description
  • Author(s): K.M. Keen
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1117 –1120
  • DOI:  10.1049/piee.1977.0232
  • Type: Article
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  • p. 1117 –1120 (4)
    A system of three computer programs is described which process data from far-field amplitude antenna pattern measurements to give partial and total directivity mappings (where ‘partial directivity’ refers to one polarisation only). The measurement data is acquired by sampling the radiation distribution over a spherical region enclosing the test antenna, first in one polarisation and then in the orthogonal polarisation, so that two ‘spheres’ of information are contained in a measurement data set. A small binary/decimal conversion program processes the two parts of the data set individually, and a data package with a heading containing measurement specifications is then set up. The data package is processed by the main program which integrates to find the isotropic level and then the partial and total directivities, and prints out the values in tabular form. As well as the conversion and main programs, there is an optional program that prints out the contents of the data package in an easily viewable form. This is useful if the input data contains errors.
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Erratum: Reappraisal of computer-corrected network analyser design and calibration
Erratum: Self-excitation of dual-excited synchronous machines
Noise reduction in integrated Norton amplifiers
Combined effects of terrestrial diffraction and ionospheric reflection on medium-frequency sky wave propagation
  • Author(s): A. Kinase
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1125 –1126
  • DOI:  10.1049/piee.1977.0236
  • Type: Article
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  • p. 1125 –1126 (2)
    A theoretical analysis is made on the titled subject as an extension of the classical theory (elaborated by H. Bremmer) of the ionospheric propagation. A physical parameter, which is akin to the conventional convergence or divergence coefficient introduced by Bremmer, is formulated in an approximate integral representation which is applicable at low to negative angles of departure/arrival, and the integral is evaluated by numerical means. Part of the result obtained from this analysis is further applied to the estimation of the interhop polarisation coupling factor, which has been formulated by G.J. Phillips and P. Knight. Striking features emerging from, and the adequacy of, the present analysis are demonstrated with a typical example.
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Rectifier circuit performance: some new approximate formulas
Interference suppression by multi-interval integration in analogue-digital convertors
  • Author(s): D. Velašević
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1135 –1138
  • DOI:  10.1049/piee.1977.0238
  • Type: Article
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  • p. 1135 –1138 (4)
    A generalised conception of multi-interval integration for the solution of the problem of interference suppression in integrating analogue-digital (a.d.) convertors is presented. Three types of multi-interval integration are described namely nonoverlapped, overlapped and combined. The characteristics of a number of corresponding integration techniques are given in tabular form for several indices of performance particularly chosen for comparison. Special attention is devoted to the increase of the line-frequency suppression. For several integration techniques, an exceptionally high line-frequency suppression, practically without loss in conversion speed, is obtained. Aspects of realisation are also discussed.
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Differential coding of Pal video signals using intrafield prediction
  • Author(s): V.G. Devereux
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1139 –1147
  • DOI:  10.1049/piee.1977.0239
  • Type: Article
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  • p. 1139 –1147 (9)
    The paper discusses the application of differential pulse-code modulation (d.p.c.m.) and hybrid d.p.c.m./p.c.m. coding as a means of reducing the bit rate required for broadcast-quality System I (Pal, 625-line, 5.5 MHz) video signals. In the d.p.c.m. codes investigated, each codeword indicated the difference in magnitude between a sample of a video signal and a prediction of this sample based on samples already transmitted in the same and/or previous line periods with a sampling frequency equal to three times the colour subcarrier frequency. The codes examined required the transmission of between 3 and 6 bits per sample. Subjective test results are given for the picture impairment caused by quantising errors and transmission errors. The tests on quantising errors indicated that d.p.c.m. could provide a saving of nearly 2 bits per sample compared with p.c.m. A comparison of subjective test results and measurements of the r.m.s. quantising errors for d.p.c.m. and p.c.m. indicates that the picture impairment corresponding to a given signal/noise ratio is similar for both d.p.c.m. and p.c.m.
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High-speed regeneration of phase-shift keying signals using phase-script logic
  • Author(s): J.L. Hobdell  and  P.A. Watson
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1148 –1154
  • DOI:  10.1049/piee.1977.0240
  • Type: Article
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  • p. 1148 –1154 (7)
    A novel method of regeneration of digital phase-modulated (phase-shift keying) signals is proposed, analysed and demonstrated using a parametric-subharmonic oscillator (p.s.o.) as a phase-script logic element. This technique of regeneration proceeds at carrier frequency without the need for down-conversion. An analysis of the switching performance of such regenerators is presented and applied to two specific circuit realisations. A switch-on time of 2ns and switch-off time of 1.5ns have been measured with a varactor diode p.s.o. at 8.2 GHz, hence demonstrating the feasibility of regeneration at 150 Mbits. A working regenerator is demonstrated at 4 GHz with a measurement of signal-to-noise/error-rate performance at 10 Mbits.
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Crossmodulation in ring modulators
Equivalent network of a variable-height post in a rectangular waveguide
Net coding gain of error-correcting codes
Net coding gain of error-correcting codes
Turbogenerator short circuits with delayed current zeros
  • Author(s): L.S. Lim  and  I.R. Smith
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1163 –1169
  • DOI:  10.1049/piee.1977.0245
  • Type: Article
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  • p. 1163 –1169 (7)
    It has been observed in practice that, following a fault at the terminals of a synchronous generator, the armature currents may not pass through zero for some considerable time, and this phenomenon may result in serious damage to a generator breaker attempting to interrrupt the fault current. In this paper, the various factors which affect the non-zero time are investigated. An analytical study is made of the 3-phase fault, to illustrate the importance of the various machine parameters and the prefault-load conditions. Unbalanced faults are considered with the aid of a digitial-computer solution of the phase-variable equations of the machine. Using this phase model, the study is extended to include a delta-star connected generator transformer, and the effects of sequential interruption of the fault currents and the arc in the generator breaker are also investigated. In particular, it is demonstrated that the redistribution of current following the interruption of one phase will considerably reduce the non-zero time in the phase worst affected, and that the breaker arc, by inducing earlier current zeros, also has a major mitigating effect on the non-zero problem.
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Implementation of new approach to determination of synchronous-machine parameters from tests
  • Author(s): G. Shackshaft  and  A.T. Poray
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1170 –1178
  • DOI:  10.1049/piee.1977.0246
  • Type: Article
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  • p. 1170 –1178 (9)
    This is a follow-up to a published paper dealing with a new theory on the analysis of the results of tests on generators in order to determine electromagnetic parameters. The application of the new theory to tests such as sudden stator short-circuit tests, stator-decrement tests, rotor-decrement tests and frequency-response tests is discussed, and examples of the analysis of such tests are presented. Further analysis, using the new theory, of the published results of tests carried out by the CEGB at Goldington and Northfleet power stations, solves some of the problems which were encountered in the original analyses of these tests. Many comparisons are made between old and new-theory results to demonstrate the worth of the latter.
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Discussion on “Transient voltages and currents in series-compensated e.h.v. lines”
Heating in transformer cores due to radial leakage flux. Part 2: Computed results
  • Author(s): C.J. Carpenter ; K.O. Sharples ; M. Djurović
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1181 –1186
  • DOI:  10.1049/piee.1977.0248
  • Type: Article
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  • p. 1181 –1186 (6)
    The experimental loss and flux-density distributions, given in the companion paper for two full-scale transformer core-leg models, are compared with theoretical results obtained by computer. The computer program provides a 3-dimensional solution of the leakage flux distribution, both outside and inside the core. The flux penetration into the core leg is calculated using an anisotropic-core model, which gives the loss distribution due to the currents induced in the laminations. The predicted and measured flux-density distributions are in good agreement. Predicted loss distributions are consistent with those obtained from rates of rise of temperature, but measurement difficulties limit the accuracy of the comparison.
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Three-dimensional theory of eddy-current couplings with copper-faced loss drums
  • Author(s): E.J. Davies ; M.T. Wright ; H. McKibbin
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1187 –1196
  • DOI:  10.1049/piee.1977.0249
  • Type: Article
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  • p. 1187 –1196 (10)
    The paper gives a 3-dimensional theory of eddy-current couplings with solid-iron drums, with a layer of copper at the airgap surface. It is shown that the iron has a significant effect on performance and that this effect can be adequately accounted for using linear theory. General double-Fourier series are derived to describe the field distributions in the drum and airgap. These are then successively simplified by taking account of the practical range of values for the permeability and resistivity of copper and iron to give design equations from which power loss and torque can be easily calculated. It is demonstrated that, under limiting conditions, the 3-dimensional theory agrees with existing end-effect theories, and that these are special cases of the more general theory presented. Experimental and theoretical torque/slip curves are compared and shown to agree. Generalised curves are deduced from the theory, which are also shown to agree closely with test results.
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Construction of Lyapunov function for power systems
  • Author(s): H. Miyagi  and  T. Taniguchi
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1197 –1202
  • DOI:  10.1049/piee.1977.0250
  • Type: Article
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  • p. 1197 –1202 (6)
    A systematic procedure of constructing Lyapunov functions for power systems is considered. A new approach is presented, which uses a construction technique of the Lagrange's function resulting from 2nd-order ordinary differential equations. The application of this new method to power-system transient-stability problems is illustrated by considering a single-machine system, taking into account the effect of the velocity governor, which is represented by 1st-order or 2nd-order response. The Lyapunov functions may then be used to estimate the critical reclosing time for power-system transient stability. The critical reclosing times given by these Lyapunov functions are compared with those obtained by numerical integration, and numerical results are shown. Further-more, it is discussed how a Lyapunov function indicates the relative effects of control-system parameters on the stability characteristic of a generator.
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Behaviour of contactors protected by fuses during short-circuit currents
Some new solutions to ferroresonance problem in power system
  • Author(s): S. Prusty  and  S.K. Sanyal
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1207 –1211
  • DOI:  10.1049/piee.1977.0252
  • Type: Article
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  • p. 1207 –1211 (5)
    A parametric equation of the envelope on the G−1(jw) plane for the general polynomial-type nonlinearity is derived. An analytical method has been suggested for the evaluation of threshold frequency for the occurrence of ferroresonance. Mathematical equations have been deduced for computing the jump-to points for quintic nonlinearity. A generalised equation for asymptotic values of percentage unstable zone for various types of nonlinearities has been derived. New definitions for jump-up severity and jump-down severity are introduced. A system due to Swift has been analaysed for the purposes of illustration.
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Theory of resistance commutation with particular reference to carbon-fibre brushes
Unifying approach to the static torque of stepping-motor structures
  • Author(s): M.R. Harris ; V. Andjargholi ; P.J. Lawrenson ; A. Hughes ; B. Ertan
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1215 –1224
  • DOI:  10.1049/piee.1977.0254
  • Type: Article
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  • p. 1215 –1224 (10)
    Important stepping-motor structures are compared and their logical relationship to a basic doubly-salient machine is demonstrated. This leads to a single expression for holding torque, applicable to the majority of motors, comprising a product of the following terms: (a) a theoretical limiting mean torque, (b) a factor allowing for finite excitation, (c) the fraction of rotor volume effectively utilised on any one step, (d) a shape factor for the torque/angle curve. The analysis is cast in dimensionless form, both in respect of component terms in the torque expression and of motor variables. In particular, a critical value of m.m.f., calculable from gap geometry, is shown to be the significant unit of applied excitation. Advantages offered by this approach are quick calculation, a ready means of comparing different motors and insight into physical behaviour. Sample calculations are presented for a variety of motors and several individual problems discussed. Support for the theory is also provided by a range of experimental work and an appraisal of commercial data.
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Comparison of nonlinear programming techniques for the optimal design of transformers
  • Author(s): G. Sridhara Rao ; V.V. Sastry ; P. Venkata Rao
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1225 –1226
  • DOI:  10.1049/piee.1977.0255
  • Type: Article
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  • p. 1225 –1226 (2)
    In many papers on the application of nonlinear programming techniques to the solution of engineering problems, such as an induction-motor design, the sequential unconstrained minimisation technique is adopted. It is shown in the paper that a nonsequential approach will lead to the same end results with much less computational time. In addition it is shown that a considerable saving in computational time could be achieved in transformer design optimisation by considering the whole problem to consist of a single constraint such as the cost function, with the sum of all suitably weighted constraints on the design performances being brought under the objective function evaluation.
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New form of inverter-fed synchronous motor with induced excitation
New form of inverter-fed synchronous motor with induced excitation
Some displays for computer-analysed speech
  • Author(s): F. Fallside  and  S. Brooks
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1227 –1229
  • DOI:  10.1049/piee.1977.0258
  • Type: Article
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  • p. 1227 –1229 (3)
    The classical displays used in speech analysis are the spectrum for single sounds and the spectrograph for continuous speech. Recent work using linear prediction analysis has led to the display of the vocal tract area function and this has been found useful in the speech training of single sounds for the deaf. The paper describes the extension of the area function to an areagraph display for continuous speech. This has been developed for the training of continuous speech, and various forms of the areagraph are described and compared with the spectrograph. Areagraph displays are also thought to be potentially useful in applications other than speech training.
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Linear proportional navigation: an exact solution for a 3rd-order missile system
Stability tests for one- two- and multidimensional linear systems
  • Author(s): E.I. Jury
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1237 –1240
  • DOI:  10.1049/piee.1977.0260
  • Type: Article
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  • p. 1237 –1240 (4)
    The paper reviews analytical stability tests for 1-dimensional linear systems since the early tests of E.J. Routh in his famous Adams Prize essay of 1877. The historical background of Routh's stability test and criterion, as well as Fuller's conjecture on its simplification, will be mentioned. In the historical review, the works of Hermite, Sylvester, Maxwell and others as related to the stability problem are also discussed. This review provides the context for a discussion of recent stability tests obtained for 2-dimensional and multidimensional linear systems. These tests are described and their computational complexity discussed in detail. In addition, the applications of stability testing to the study of 2- and multidimensional digital filters, numerical analysis of stiff-differential equations, realisation of mixed lumped- and distributed parameter systems, and the design of output feedback systems will be briefly mentioned. Comments on future research in this area conclude the review.
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Analytic application of Tsypkin's method relay with hysteresis and dead zone
Synthesis of stable and optimal controllers for a 2-shaft gas turbine
Stochastic state-variable model for a paper-machine headbox
  • Author(s): S.K. Sud ; K.K. Biswas ; A.K. Sinha
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1249 –1254
  • DOI:  10.1049/piee.1977.0263
  • Type: Article
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  • p. 1249 –1254 (6)
    A state-variable model for a pilot plant of paper-machine headbox has been developed using actual input-output data. The linearised physical equations have been considered and effects of plant disturbance and measurement errors have been included. For estimating the unknown parameters of the model from noisy measurements, two recursive estimation techniques, namely ‘extended Kalman filter’ and ‘two-stage estimation algorithm’, have been used. The model validity has been checked by carrying out residual error tests for both the techniques. Further, estimated responses in both the cases have been compared with the actual output.
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Design of an improved gas-turbine controller
Feedback electrostatic wattmeter using a noncontact moving-coil actuator
  • Author(s): B.E. Jones  and  N.A. Mirza
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1259 –1262
  • DOI:  10.1049/piee.1977.0265
  • Type: Article
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  • p. 1259 –1262 (4)
    An electrostatic wattmeter employing automatic torque balance about a taut-band suspension has been developed. The only direct physical electrical connection to the suspension assembly is the normal load voltage connection to the vane of the quadrant electrometer. The feedback torque is provided by a noncontact precision actuator which consists of an inductive coupling to a moving coil fixed on the suspension assembly, and which uses magnetic field variation. Suspension angular displacement is determined by using the quadrant structure as a push-pull capacitance transducer. The experimental instrument provides a d.c. output proportional to load power whether the supply is a.c. or d.c. It has linearity of at least ±0.5% over its measuring range, and the instrument calibration is essentially independent of power supply voltages and load power factors. It is easy to set the zero, but zero drift has a temperature sensitivity of about 1% per degree centigrade. No special antivibration mount is used, and typical noise at the instrument output (without a lowpass filter) has a peak-peak value of about 5% of full-scale reading. The transducer bridge circuit limits the range of power frequencies that can be measured. Improvements to reduce drift and noise effects are proposed, and the use of an optical position detector is suggested.
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Photographic investigation of breakdown of composite insulation
Exterior finite elements for 2-dimensional field problems with open boundaries
  • Author(s): P.P. Silvester ; D.A. Lowther ; C.J. Carpenter ; E.A. Wyatt
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1267 –1270
  • DOI:  10.1049/piee.1977.0267
  • Type: Article
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  • p. 1267 –1270 (4)
    Electric- and magnetic-field problems with boundaries at infinity are treated in finite-element terms by constructing an element to model an extremely large annulus surrounding the region of interest. A simple recursion technique is employed to generate the matrix representing the annular region. All nodes are eliminated from the external element except those on its inner surface, so that the final matrix is no larger than that required to describe the region of interest only. The method is simpler to program and requires less computing effort than boundary-integral techniques. It has been tested by solving several 2-dimensional magnetostatic and electrostatic problems and comparing the results with analytic solutions. The method can be applied to any 2-dimensional field problem bounded by a large empty region in which the field satisfies Laplace's equation.
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Monte Carlo field calculations
  • Author(s): J.H. Pickles
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1271 –1276
  • DOI:  10.1049/piee.1977.0268
  • Type: Article
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  • p. 1271 –1276 (6)
    The paper is concerned with a method of calculating potentials and fields that is particularly suited to engineering problems with complicated 3-dimensional geometries. The method solves Laplace's equation numerically using a floating random-walk technique. The efficiency of the basic method can be improved substantially by some simple generalisations, and potential gradients can be calculated directly, as well as the potentials themselves. Examples are given of problems that have arisen in high-voltage engineering for which the potentials and fields have been calculated using a computer program based on the generalised method.
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Electrostatic potential and field in a cylindrical tank containing charged liquid
  • Author(s): K. Asano
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1277 –1281
  • DOI:  10.1049/piee.1977.0269
  • Type: Article
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  • p. 1277 –1281 (5)
    If a metal tank is partly filled by charged liquid, such as hydrocarbons, the electrostatic potential can become very high and hazardous. In order to determine this potential, one must solve the Poisson and the Laplace equations simultaneously. With a cylindrical tank configuration, an analytical solution was obtained by using Bessel functions. Numerical computation of the model was performed and it can be shown that the convergence of the series solution is reasonably acceptable. The computed results are shown for a particular model. In order to estimate a maximum potential and field strength in the gas space for general configuration of a tank, more practical equations were derived.
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Simulation of transient and steady-state magnetisation characteristics with hysteresis
Reply: Simulation of transient and steady-state magnetisation characteristics with hysteresis
Novel method of calculation of eddy-current losses induced by a.c. flowing through conductors

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