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Volume 124
Issue 12
Proceedings of the Institution of Electrical Engineers
Volume 124, Issue 12, December 1977
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Volume 126 (1979)

Volume 125 (1978)

Volume 124 (1977)

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Volume 124, Issue 12
December 1977
Evaluation of beamscanning dualreflector antennas
 Author(s): G. Tong ; P.J.B. Clarricoats ; G.L. James
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1111 –1113
 DOI: 10.1049/piee.1977.0230
 Type: Article
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The gain/scan characteristics of four different types of dualreflector antenna are compared. The theoretical analysis is based on the receive mode of operation in which geometrical optics, geometrical theory of diffraction and physicaloptics technique are applied. Measured results of one of the designed antenna are found to agree well with prediction.
Some resonance effects in scattering of microwaves by hydrometeors
 Author(s): A.R. Holt and B.G. Evans
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1114 –1116
 DOI: 10.1049/piee.1977.0231
 Type: Article
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Investigation of the polarisation properties of scattered electromagnetic waves from spheroidal raindrops in the microwave region has resulted in the discovery of a resonance effect at 6 GHz. The behaviour of the scattering amplitudes and crosspolarisation of several drop sizes are shown. It is further shown that such effects occur at millimetre wave frequencies for ice particles, an example being given at 30 GHz.
Computerprogram description. Computerprogram system for evaluating partial and total antenna directivities from measured data. Computerprogram 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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A system of three computer programs is described which process data from farfield 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.
Erratum: Reappraisal of computercorrected network analyser design and calibration
 Author(s): D. Woods
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, page: 1120 –1120
 DOI: 10.1049/piee.1977.0233
 Type: Article
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Erratum: Selfexcitation of dualexcited synchronous machines
 Author(s): J. Nanda and S. Hurry
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, page: 1120 –1120
 DOI: 10.1049/piee.1977.0234
 Type: Article
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Noise reduction in integrated Norton amplifiers
 Author(s): J.W. Haslett and A. Krausas
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1121 –1124
 DOI: 10.1049/piee.1977.0235
 Type: Article
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The effects of currentmirror emitter degeneration on monolithic Norton amplifier operation are described. The limits on practical improvement in noise performance obtainable are discussed. An active filter is used to illustrate the substantial noise reduction that can be achieved over standard handbook designs, and the predictions are verified experimentally.
Combined effects of terrestrial diffraction and ionospheric reflection on mediumfrequency 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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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.
Rectifier circuit performance: some new approximate formulas
 Author(s): A.G. Bogle
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1127 –1134
 DOI: 10.1049/piee.1977.0237
 Type: Article
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New formulas are offered for the calculation of the performance parameters of halfwave and fullwave rectifiers: average output voltage, effective and peak values of diode current, peakpeak ripple and ‘trough’ value of output voltage (the lower extreme of the ripple). These are expressed in terms of the impedance and frequency of the a.c. source, the size of the reservoir capacitor and the load current or the load resistance, depending on which is in practice constant. The formulas are convenient provided that an electronic calculator is available.
Interference suppression by multiinterval integration in analoguedigital 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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A generalised conception of multiinterval integration for the solution of the problem of interference suppression in integrating analoguedigital (a.d.) convertors is presented. Three types of multiinterval 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 linefrequency suppression. For several integration techniques, an exceptionally high linefrequency suppression, practically without loss in conversion speed, is obtained. Aspects of realisation are also discussed.
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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The paper discusses the application of differential pulsecode 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 broadcastquality System I (Pal, 625line, 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.
Highspeed regeneration of phaseshift keying signals using phasescript 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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A novel method of regeneration of digital phasemodulated (phaseshift keying) signals is proposed, analysed and demonstrated using a parametricsubharmonic oscillator (p.s.o.) as a phasescript logic element. This technique of regeneration proceeds at carrier frequency without the need for downconversion. An analysis of the switching performance of such regenerators is presented and applied to two specific circuit realisations. A switchon time of 2ns and switchoff 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 signaltonoise/errorrate performance at 10 Mbits.
Crossmodulation in ring modulators
 Author(s): H.J. Bex
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1155 –1159
 DOI: 10.1049/piee.1977.0241
 Type: Article
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This paper deals with the crossmodulation in ring modulators. By means of an approximate calculation the effective halfvalue of the e.m.f. of the undesired signal at the input of the ring modulator, giving rise to a crossmodulation factor of 1%, is investigated as a function of the maximum available power of the oscillator. The results of the theory used here show very good agreement with the measurements.
Equivalent network of a variableheight post in a rectangular waveguide
 Author(s): V.M. Pandharipande and B.N. Das
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1160 –1162
 DOI: 10.1049/piee.1977.0242
 Type: Article
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Net coding gain of errorcorrecting codes
 Author(s): V.K. Bhargava and M. Avni
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, page: 1162 –1162
 DOI: 10.1049/piee.1977.0243
 Type: Article
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Net coding gain of errorcorrecting codes
 Author(s): J.H. Blythe and K. Edgcombe
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, page: 1162 –1162
 DOI: 10.1049/piee.1977.0244
 Type: Article
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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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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 nonzero time are investigated. An analytical study is made of the 3phase fault, to illustrate the importance of the various machine parameters and the prefaultload conditions. Unbalanced faults are considered with the aid of a digitialcomputer solution of the phasevariable equations of the machine. Using this phase model, the study is extended to include a deltastar 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 nonzero time in the phase worst affected, and that the breaker arc, by inducing earlier current zeros, also has a major mitigating effect on the nonzero problem.
Implementation of new approach to determination of synchronousmachine 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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This is a followup 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 shortcircuit tests, statordecrement tests, rotordecrement tests and frequencyresponse 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 newtheory results to demonstrate the worth of the latter.
Discussion on “Transient voltages and currents in seriescompensated e.h.v. lines”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1178 –1180
 DOI: 10.1049/piee.1977.0247
 Type: Article
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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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The experimental loss and fluxdensity distributions, given in the companion paper for two fullscale transformer coreleg models, are compared with theoretical results obtained by computer. The computer program provides a 3dimensional solution of the leakage flux distribution, both outside and inside the core. The flux penetration into the core leg is calculated using an anisotropiccore model, which gives the loss distribution due to the currents induced in the laminations. The predicted and measured fluxdensity 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.
Threedimensional theory of eddycurrent couplings with copperfaced 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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The paper gives a 3dimensional theory of eddycurrent couplings with solidiron 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 doubleFourier 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 3dimensional theory agrees with existing endeffect 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.
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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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 2ndorder ordinary differential equations. The application of this new method to powersystem transientstability problems is illustrated by considering a singlemachine system, taking into account the effect of the velocity governor, which is represented by 1storder or 2ndorder response. The Lyapunov functions may then be used to estimate the critical reclosing time for powersystem transient stability. The critical reclosing times given by these Lyapunov functions are compared with those obtained by numerical integration, and numerical results are shown. Furthermore, it is discussed how a Lyapunov function indicates the relative effects of controlsystem parameters on the stability characteristic of a generator.
Behaviour of contactors protected by fuses during shortcircuit currents
 Author(s): G. Cantarella ; G. Farina ; M. Tartaglia
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1203 –1206
 DOI: 10.1049/piee.1977.0251
 Type: Article
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The behaviour of contactors protected by fuses under shortcircuit currents is analysed using a simple model to represent the electric circuit and the contactor. The resulting performance equations are given and an example of application is illustrated. Experimental results are reported which agree well with those computed. The existence is confirmed of a definite range of prospective shortcircuit currents in which the protective action of the fuse lets through the most severe stress experienced by the contactor.
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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A parametric equation of the envelope on the G^{−1}(jw) plane for the general polynomialtype 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 jumpto 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 jumpup severity and jumpdown severity are introduced. A system due to Swift has been analaysed for the purposes of illustration.
Theory of resistance commutation with particular reference to carbonfibre brushes
 Author(s): J.J. Bates and J.W. Skinner
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1212 –1214
 DOI: 10.1049/piee.1977.0253
 Type: Article
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Commutation in small machines depends on changing brushsegment resistances. The manner in which these resistances change, and the consequent brush current densities, can be influenced by the shape of the commutator segments. Simple equations are derived from the current density during commutation, and these are used to show that specially shaped segments can lead to lower maximum values. This conclusion has been verified using carbonfibre brushes and faceplate commutators.
Unifying approach to the static torque of steppingmotor 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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Important steppingmotor structures are compared and their logical relationship to a basic doublysalient 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.
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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In many papers on the application of nonlinear programming techniques to the solution of engineering problems, such as an inductionmotor 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.
New form of inverterfed synchronous motor with induced excitation
 Author(s): R. Krishnan and B. Ilango
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, page: 1226 –1226
 DOI: 10.1049/piee.1977.0256
 Type: Article
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New form of inverterfed synchronous motor with induced excitation
 Author(s): A.C. Williamson and B.J. Chalmers
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, page: 1226 –1226
 DOI: 10.1049/piee.1977.0257
 Type: Article
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Some displays for computeranalysed 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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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.
Linear proportional navigation: an exact solution for a 3rdorder missile system
 Author(s): G.C. Holt
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1230 –1236
 DOI: 10.1049/piee.1977.0259
 Type: Article
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A 3rdorder missile system is considered, and an exact solution found with the aid of the adjoint technique. The solution takes the form of an infinite power series and enables the miss distance due to noise and target manoeuvre to be calculated. An indication of missile lateral acceleration (latax) is also given.
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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The paper reviews analytical stability tests for 1dimensional 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 2dimensional 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 stiffdifferential 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.
Analytic application of Tsypkin's method relay with hysteresis and dead zone
 Author(s): S.R. Atre and V.P. Lele
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1241 –1242
 DOI: 10.1049/piee.1977.0261
 Type: Article
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A method is developed whereby the periodic component of the output of a selfoscillating relay system is obtained without utilising the Fourier series expansion. This way the infinite sums encountered in the application of Tsypkin's method are avoided and in their place analytic expressions for the real and imaginary parts of Tsypkin functions are arrived at. These results are applied to systems containing relay elements having hysteresis and dead zone.
Synthesis of stable and optimal controllers for a 2shaft gas turbine
 Author(s): R.N. Tiwari ; P. Purkayastha ; S.N. Tiwari
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1243 –1248
 DOI: 10.1049/piee.1977.0262
 Type: Article
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In this paper, poleplacement technique, Lyapunov's direct method and optimal linear stateregulator formulation are employed to design stable and optimal controllers for a 2shaft gas turbine using the model proposed by Mueller. Analysis and comparison of smallsignal transient behaviour of the original system and system with controller are also given.
Stochastic statevariable model for a papermachine 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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A statevariable model for a pilot plant of papermachine headbox has been developed using actual inputoutput 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 ‘twostage 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.
Design of an improved gasturbine controller
 Author(s): O.A. Sebakhy and N.N. Sorial
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1255 –1258
 DOI: 10.1049/piee.1977.0264
 Type: Article
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Based on the ‘internal model principle’, a controller is designed for a gas turbine. The resulting controlled system has a stable closed loop, and furthermore no offsets occur in the output variables owing to the presence of disturbance representing the change of altitude. The system preserves these properties in spite of small changes in system parameters. The suggested controller is compared with other known types of controllers.
Feedback electrostatic wattmeter using a noncontact movingcoil 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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An electrostatic wattmeter employing automatic torque balance about a tautband 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 pushpull 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 peakpeak value of about 5% of fullscale 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.
Photographic investigation of breakdown of composite insulation
 Author(s): D.W. Auckland ; A.B. Borishade ; R. Cooper
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, p. 1263 –1266
 DOI: 10.1049/piee.1977.0266
 Type: Article
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The alternating and impulsevoltage breakdown of a composite consisting of a column of air in series with a solid dielectric layer has been investigated. Breakdown is initiated in the solid some 60 ns before voltage collapse, and not by the establishment of a plasma throughout the air column, as supposed by a current hypothesis. This is also true for a liquid/solid composite.
Exterior finite elements for 2dimensional 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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Electric and magneticfield problems with boundaries at infinity are treated in finiteelement 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 boundaryintegral techniques. It has been tested by solving several 2dimensional magnetostatic and electrostatic problems and comparing the results with analytic solutions. The method can be applied to any 2dimensional field problem bounded by a large empty region in which the field satisfies Laplace's equation.
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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The paper is concerned with a method of calculating potentials and fields that is particularly suited to engineering problems with complicated 3dimensional geometries. The method solves Laplace's equation numerically using a floating randomwalk 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 highvoltage engineering for which the potentials and fields have been calculated using a computer program based on the generalised method.
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
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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.
Simulation of transient and steadystate magnetisation characteristics with hysteresis
 Author(s): L.I. Williams and P. Atkinson
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, page: 1281 –1281
 DOI: 10.1049/piee.1977.0270
 Type: Article
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Reply: Simulation of transient and steadystate magnetisation characteristics with hysteresis
 Author(s): D. O'Kelly
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, page: 1281 –1281
 DOI: 10.1049/piee.1977.0271
 Type: Article
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p.
1281
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Novel method of calculation of eddycurrent losses induced by a.c. flowing through conductors
 Author(s): M.R. Krakowski
 Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 12, page: 1282 –1282
 DOI: 10.1049/piee.1977.0272
 Type: Article
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p.
1282
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A method of calculation of the eddycurrent losses which are produced within a conducting solid by a.c. flowing through cylindrical or ribbon conductors is presented. The eddycurrent losses are expressed in terms of the mutual and external resistances of the conductors in presence of the solid. The method presented permits the computation of eddycurrent losses withoutintegrating the Poynting vector.
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