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Volume 118
Issue 10
Proceedings of the Institution of Electrical Engineers
Volume 118, Issue 10, October 1971
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Volume 126 (1979)

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Volume 118, Issue 10
October 1971
Application of incoherentscatter data to communication
 Author(s): G.N. Taylor
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1319 –1322
 DOI: 10.1049/piee.1971.0247
 Type: Article
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The application of a very sensitive radar system to the observation of signals incoherently scattered in the ionosphere is briefly described. This technique can give more detailed information about height and time variations of bottomside electrondensity profiles than any other method, besides measuring several further parameters of the plasma. Electrondensity profiles of the daytime lower Eregion, and of the whole of the nighttime Eregion, allow much more reliable estimates than hitherto to be made of nondeviative h.f. absorption, and of the reflection heights of m.f. and l.f. waves. The morphology of the ‘valley’ in the profile between the E and Fregions can be investigated; also the ability to measure details of profile changes during ionospheric disturbances should allow the accompanying deterioration in h.f. propagation conditions to be understood. Incoherentscatter measurements give unique opportunities of making independent calibrations of statellite instruments in orbit, and of measuring plasma movements induced by neutral aid winds. An empirical law relating the temperature and density of the electrons has been discovered; this will help in predicting the changes in density which should occur when additonal heat energy is deposited in the ionosphere during disturbances.
Use of flayer theory in ionospheric predictions
 Author(s): H. Rishbeth
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1323 –1326
 DOI: 10.1049/piee.1971.0248
 Type: Article
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Worldwide predictions of h.f. and m.f. radio propagation conditions require extensive data on the space and time variations of ionospheric parameters such as foF2 and h_{m}F2. Theoretical values of these parameters can be obtained by solving equations that represent the effects of various physical processes governing Flayer behaviour. The effects of winds, which are driven by the daily heating of the upper atmosphere, on the midlatitude F2layer are briefly described. Consideration is also given to the polar and the lowaltitude F2layer and to problems of Flayer storms.
Theory of cylindrical antennas with arbitrary impedance loading
 Author(s): B.D. Popović
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1327 –1332
 DOI: 10.1049/piee.1971.0249
 Type: Article
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A method of analysing cylindrical antennas with distributed impedance loading is presented. The loading is assumed to be an arbitrary but differentible function of position along the antenna. As an illustration, the most important class of such antennas in practice, the broadband cylindrical antennas with distributed resistive or capacitive loading, for which exprimental data are available, are analysed. The theoretica results are in satisfactory agreement with experiments.
Analysis of multicomponent wavefields
 Author(s): P.J.D. Gething
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1333 –1338
 DOI: 10.1049/piee.1971.0250
 Type: Article
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The problem considered is that of clculating the angles of arrival of a multimoded signal at an antena array from simultaneous measurements of the amplitude and the phase of the signal in each element of the array. A general solution with wide application is described.
Factors influencing conversion efficiency in gaseousplasma harmonic generators working at microwave frequencies
 Author(s): J.R. Riley
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1339 –1344
 DOI: 10.1049/piee.1971.0251
 Type: Article
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This paper describes a novel application of the fieldgradient theory of plasma microwave harmonic generation, proposed by Krenz and Kino, to the case of a positive column placed through a rectangular waveguide. The distribution of 2ndharmonic power between the TE_{01} and TE_{11} waveguide modes has been examined experimentally and found to be in agreement with qualitative predictions made from the gradient model. An inversecubic depence between the 2ndharmonicconversion efficiency and electroncollision frequency, predicted by Krens, has also been observed. A metal probe plaved against the column, with the intention of introducing severe microwavefield gradients in the plasma resonace at the fundamental frequency, a best overall conversion of about 25% was produced for an input power of 500mW at 2.42 GHz. At higher power levels, the plasma electron density appropriate for fundamental resonance could not be sustained, and the conversion effiency fell. Experiments using 9.6 and 35GHz fundamental signals gave best conversion efficiencies to the second harmonic of only 2.5 % and about 0.01%, respectively. It is concluded that the gradient model provides a satisfactory description of 2ndharmonic generation in gaseous plasmas, but that devices based on this model do not operate efficiently at high power levels or at high microwave frequencies.
Relativephase measurement at Q band
 Author(s): A.G. Bailey and D.G. de Mesquita
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1345 –1350
 DOI: 10.1049/piee.1971.0252
 Type: Article
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A singlesideband suppressedcarrier ferrite modulator is used in a Qband serrodyne phase bridge. By suitably processing the bridgedetector output, relative phase in the unknown bridge arm may be measured to within 1% of its true value, despite nonlinearities in both the static insertionloss and phaseshift characteristics of the modulator. The modulator drive is not critical.
V.L.F. propagation parameters derived from observations of sunrise and sunset phenomena
 Author(s): S.F. Mahmoud and J.C. Beal
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1351 –1357
 DOI: 10.1049/piee.1971.0253
 Type: Article
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Received v.l.f. signals during sunrise and sunset times over the propagation path are used to deduce information about the attenuation coefficients and phase velocities of the day and night waveguide modes, as well as the conversion factors between these modes at the day/night transition. Unlike any previous method used to obtain modal propagation constants, the present method does not need a mobile receiver, since it directly makes use of the moving secondary source formed by the mode conversion that takes place at the shadow line, or transition. A twonightmodes/twodaymodes model is discussed in detail. It is seen that it has a wider range of validity, with regard to both the path length and the frequency, than both the twonightmodes/onedaymode model suggested by Crombie in 1964, and the onenightmode/twodaymodes model used for the early part of the sunrise period by Kaiser.
Binary nonconsecutive one code for timetag data compression
 Author(s): Waihung Ng
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1358 –1360
 DOI: 10.1049/piee.1971.0254
 Type: Article
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A simple timetag datacompression scheme which uses a binary nonconsecutive one code is introduced to provide higher data compression ratios than similar schemes which have been suggested. This datacompression scheme should be very easy to implement. In addition, it does not require a priori knowledge of the information source.
Perception efficiency for radio and television displays
 Author(s): Derek Broadbent
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1361 –1362
 DOI: 10.1049/piee.1971.0255
 Type: Article
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Tests of the effect of time stress on human performance in the recognition situation were carried out using a standard television display with accompanying audio and noise sources, the student responding with a standard key punch. Reaction time and psychological moment measurements are reported and discussed.
Parametric graphical computer display system using analogue storage
 Author(s): D.J. Woollons ; H.B. Kendler ; R.L. Grimsdale
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1363 –1372
 DOI: 10.1049/piee.1971.0256
 Type: Article
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A cathoderaytube graphical display system for use as a digitalcomputer output terminal has been developed The display employs analogue functiongeneration circuits to produce line drawings composed of straightline and curvedline segments which are specified by parameters transferred from the computer in analogue form. To maintain a flickerfree image, while also imposing a minimal demand on the computer to which it is connected, the display incorporates an analogue memory composed of capacitors and fieldeffecttransistor switches. The displayed image may then be refreshed at the required rate by cyclically reading the line and curve control parameters from this memory. The computer need only access the memory to insert fresh data to be displayed or, infrequently, to refresh the stored information. The paper includes discussions of the specification of the overall display system, of the design of the analogue storage system and of two methods used to produce the required picture segments for display. Some results obtained with the display connected online to a small digital computer are shown.
Computercontrolled queuing systems with feedback
 Author(s): W.C. Chan and W.K. Chung
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1373 –1377
 DOI: 10.1049/piee.1971.0257
 Type: Article
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A generalised approach is presented for the study of a computercontrolled queuing system with general input, ‘firstcomefirstserved’ queue discipline and multiple servers with feedback for either exponential servers or constant service times. Two generating functions for the state probabilities of the system corresponding to the two different types of service times are derived. Further, necessary and sufficient conditions for the existence of statistical equilibrium of the computercontrolled queuing system are obtained from the generating functions. The results obtained here generalise many results previously obtained by other workers.
Waitingtime distribution in computercontrolled queuing system
 Author(s): W.K. Chung and W.C. Chan
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1378 –1382
 DOI: 10.1049/piee.1971.0258
 Type: Article
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The paper presents two formulas for the determination of the waitingtime distribution in a computercontrolled queuing system with Poisson input, multipleexponential servers and firstcomefirstserved queue discipline. The formulas obtained are expressed in terms of the stationarystate probabilities of the computercontrolled queuing system. One of the formulas is derived by means of the formula of total proability and the other is derived by the use of the theory of Markov chains. It is shown that, by virtue of a limiting process, the first formula obtained in the paper yields the waitingtime distribution in the conventional queuing system without computer control. Furthermore, application of the two formulas for the determination of waitingtime distribution is illustrated by an example.
Corrigendum: Use and design of 4wire telephone trunk concentrators
 Author(s): R.J. Hall
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, page: 1382 –1382
 DOI: 10.1049/piee.1971.0259
 Type: Article
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Method of using redundancy in very large computer stores
 Author(s): J.G. Axford and A.R. Fiske
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1383 –1392
 DOI: 10.1049/piee.1971.0260
 Type: Article
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The organisation of a very large randomaccess computer store which uses redundancy in the form of errorcorrecting codes is described. The improvements in manufacturing yield which can be achieved by means of such redundancy are emphasised in the form of examples. However, with typical basic store sizes in the capacity range 10^{7}−10^{8} bits, some of the most significant improvements in manufacturing yield are achieved by programmed assembly which makes use of the ease of testability of such redundant systems. The conclusion is that widespread use of the proposed technique of design and manufacture can result in significant savings, both to designer and customer.
Techniques for the measurement of source and drain series resistance in m.o.s. transistors
 Author(s): P.J.T. Mellor
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1393 –1398
 DOI: 10.1049/piee.1971.0261
 Type: Article
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Three methods for measuring the source and drain resistance of m.o.s. transistors operating in the unsaturated region are described. The results obtained on a number of simple m.o.s. transistors are presented to illustrate and compare each method and to indicate the significance of such measurements.
Simple estimators for error probability in simulation studies of digital communication systems
 Author(s): D.A. Bell ; N.A. Stewart ; T. McCudden
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, page: 1398 –1398
 DOI: 10.1049/piee.1971.0262
 Type: Article
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Thermal insulation for energy storage
 Author(s): D.J. Dickson
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1399 –1407
 DOI: 10.1049/piee.1971.0263
 Type: Article
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Efficient thermalenergy storage requires effective thermal insulation. From a consideration of the possible heattransfer modes, the requirements for a thermal barrier can be deduced. In a good conventional thermal insulation, most of the heat transfer takes place by conduction through the gas (air) in the insulation voids, the conductivity of the ‘still’ gas representing the limiting performance of such a material. It follows that a better performance can be obtained only by reducing this gasconducted heat by having voids smaller than the molecular meanfree path (‘microporous’), by replacing the air by a lowconductivity gas or by partially evacuating the insulation.
Space harmonics in unified electricalmachine theory
 Author(s): J.L. Willems
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1408 –1412
 DOI: 10.1049/piee.1971.0264
 Type: Article
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The paper deals with the applicability of unified machine theory to electrical machines where space harmonics can not be neglected. It is shown that there exists cases where a linear transformation can de determined to transform the set of timedepended linear differential equations for a machine at constant speed into a set of linear timeinvariant differential equations, even if space harmonics are taken into considertation. A criterion for applicability is presented that involves the number of phases, the number of harmonics and the order of the harmonics that have to be considered.
Performance of d.c. linear machines based on an assessment of flux distributions
 Author(s): C.W. Green and R.J.A. Paul
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1413 –1420
 DOI: 10.1049/piee.1971.0265
 Type: Article
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An analytical study is described of the magneticfield system in a d.c. linear motor. The equations derived are solved by numerical techniques based on a finitedifference approximation. A modification of existing methods is adopted to deal with heterogeneous regions of permeability. The computed flux profiles are shown to compare favourably with experimental results obtained on a 2pole machine, including the effects of armature reaction. The results are used in tahe derivation of the developed force and dynamic characteristics of a loaded machine, and the theoretical results are again shown to agree closely with experimental results.
Design of microalternator for powersystemstability investigations
 Author(s): T.J. Hammons and A.J. Parsons
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1421 –1441
 DOI: 10.1049/piee.1971.0266
 Type: Article
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The paper describes the design of a microalternator in which negativeresistance devices are employed to obtain representative constants of the model's rotor circuits. Dimensional scaling in assessing the parameters of model alternators is reviewed. Methods of calculating the model's principal constants from design data are outlined for a machine of salientpolerotor construction. Core and shortcircuit losses are examined, and the choice of design criteria is discussed. Test results for a machine of salientpole construction are given which compare very favourably with the constants derived from design considerations. Attention is also given to the special facilities which are provided by the timeconstant regulator and other associated auxiliary equipment.
Comparisons of synchronousmachine models in the study of the transient behaviour of electrical power systems
 Author(s): T.J. Hammons and D.J. Winning
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1442 –1458
 DOI: 10.1049/piee.1971.0267
 Type: Article
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Methods of modelling power systems in the study of the system transient behaviour are reviewed. Six machine models of varying complexity are developed from the fundamental machine equations. Factors in the form of the machine equations, which critically influence the economy of solution, are identified, The relationship between the machine and system equations is examined in relation to the digital solution of multimachine problems, and generalised methods of solution of the equations are outlined. Comparisons are made between results obtained from the range of machine models and those obtained from fullscale faultthrowing tests on the public supply system. In one case, a single machine connected to a system of high capacity is modelled, while, in the second example, two 60 MW machines connected to a large mulrimachine system is modelled. Both nonpoleslipping and poleslipping tests for the case of the 2machine system are examined, in which a machine marginally remained in synchronism and marginally lost synchronism, respectively. It is shown that models in which subtransient phenomena are simulated, but in which some transformer voltages in the stator equations, together with subtrasient saliency, are neglected, provide an adequate and economical model for system disturbances, including those in which the machine may fall from synchronism.
Synchronousmachine sudden 3phase shortcircuit. Analysis by norton's, constantfluxlinkage and thévenin's theorems
 Author(s): S.K. Goswami
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1459 –1466
 DOI: 10.1049/piee.1971.0268
 Type: Article
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The paper presents a new technique of analysis. Equivalent circuits, which normally omit altogether the asymmetrical and 2ndharmonic armaturecurrent components, are made to give the complete solution including the said components by applying theorems which are well known for their simplifying effect. In the first alternative, Norton's theorem is used to replace the 3phase armaturevoltage source by equivalent current sources on the direct and quadrature axes. The appropriate axis loads presented by the rest of the machine are connected to the current sources. Thus, appropriately energised equivalent circuits are obtained which give the complete solution. In the second alternative, the ‘effective’ 2axis armaturevoltage source, for shortcircuit conditions, is determined by the constantfluxlinkage theorem. Then, by Thévenin's theorem, the appropriately energised equivalent circuits are obtained which again give the complete solution.
Transient stability of power systems containing both synchronous and induction machines
 Author(s): S.S. Kalsi and B. Adkins
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1467 –1474
 DOI: 10.1049/piee.1971.0269
 Type: Article
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A method is described of calculating the effect of large induction motors on the transient performance of a multimachine power system under fault conditions. The representation of an induction motor is similar to that used for synchronous machines, and is therefore suitable for describing composite systems. The method is based on Park's equations and, unlike earlier methods, allows for the ‘deepbar effect’ usually present in large cage induction motors. The most accurate result is obtained by using the full set of equations, but more approximate methods using simplified equations are considered. The method is verified by tests on model machines connected by impedances representing transmission lines. Preliminary tests were made on a simple system comprising an induction motor connected to an infinite busbar through an impedance, and were followed by tests on a composite system containing a synchronous machine and an induction motor connected in parallel parts of the system. The results slow that good results are obtained with the accurate calculation which, however, requires a large amount of computer time, but that any approximation introduces considerable error.
Discussion on “Starting methods for generator/motor units employed in pumpedstorage stations” and “Investigation into dampingtorque coefficients and stability of a 2synchronousmachine system employed in synchronous starting”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1475 –1485
 DOI: 10.1049/piee.1971.0270
 Type: Article
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Design and parameters affecting the surface stress of overheadpowerline conductor systems
 Author(s): R.N. Allan and J.E.J. Cottrill
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1486 –1492
 DOI: 10.1049/piee.1971.0271
 Type: Article
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To prevent undue radio interference and energy loss from overhead conductors, the permissible operating stress must be minimised. Therefore, the design of such conductors was investigated theoretically using a conformal transformation proposed by Timascheff. First, the effect of the design parameters, that is, the subconductor diameter, subconductor spacing, number of subconductors and phase spacing on the maximum surface stress, was considered. This showed that the surface stress decreases as the subconductor diameter, number of subconductors and phase spacing is increased. It also showed that there is an optimum subconductor spacing at which the surface stress is a minimum. Secondly, an equation defining the optimum subconductor spacing was determined. From this equation, it was found that the optimum spacing is affected by all the other parameters, and that subconductor spacings close to the optimum can be justified economically. Finally, the general design of conductor systems was discussed, and possible conductors for a 765kV system were computed using optimum spacings. This showed that the total conductor material is considerably reduced and that the overall diameter of the bundle remains unchanged with an increasing number of subconductors. A suggested computational method for determining possible conductor systems was also described.
Design for a superconducting a.c. power cable
 Author(s): E.C. Rogers ; R.J. Slaughter ; D.A. Swift
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1493 –1500
 DOI: 10.1049/piee.1971.0272
 Type: Article
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The paper describes a design study for a 750 MVA 33 kV superconducting a.c. power cable. Conductor and dielectric design, thermal insulation and refrigeration and methods of construction and installation are all considered. Niobium is the chosen conductor material, and a triple coaxial construction the chosen conductor geometry. The capital costs of the systems considered are estimated to be rather more than twice that of the equivalent 275kV conventional oilfilled cables. The running costs are about the same as that of the conventional equivalent, but represent only a small proportion of the total cost. Problems which need further study and development work, and whose solution could lead to significant design improvements and cost reductions, are: (a) protection of the conductors against current overload, (b) thermal contraction and (c) dielectric design. It is concluded that, though superconducting cables are unlikely to be economical at the power level considered in the study, they may find application in the multiGVA region.
Corrigendum: Influence of conductor designs and operating temperature on the economics of overhead lines
 Author(s): P. Dey ; B. Gaylard ; C.W. Mott ; J.A. Nicholson
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, page: 1500 –1500
 DOI: 10.1049/piee.1971.0273
 Type: Article
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Fullwave rectifier with constantcurrent load
 Author(s): M.R. Westcott
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1501 –1502
 DOI: 10.1049/piee.1971.0274
 Type: Article
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Design of digital controllers for randomly disturbed systems
 Author(s): D.W. Clarke and R. HastingsJames
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1503 –1506
 DOI: 10.1049/piee.1971.0275
 Type: Article
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The paper presents a method of designing digital controllers for randomly disturbed singleinput/singleoutput linear systems with time delay which minimise the cost function E{y^{2}_{t+k}+λu^{2}_{t}}. The process and noise models used are those obtained from current identification programs, and the control law developed has significant advantages over standard minimumvariance designs. (a) There is no difficulty with nonminimumphase systems. (b) For processes with constraints on control effort, a marked improvement in the resultant output variance can be achieved. (c) There is a flexibility in the design to deal with cases where the closedloop performance becomes unsatisfactory because of parameter drift or other causes. A typical example of the design procedure is given, and a comparison between the new control law and a minimumvariance law is made.
Determination of the least order of transferfunction matrices
 Author(s): N. Munro
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1507 –1510
 DOI: 10.1049/piee.1971.0276
 Type: Article
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The problem of determining the least order of transferfunction matrices without computing a minimal realisation is considered. A new method is developed for determining the least order of a proper transferfunction matrix, and an algorithm is presented which is computationally attractive.
Nonlinear analysis of a 1storder thyristorbridge control system. Use of difference equations and transition mapping
 Author(s): J.O. Flower and P.A. Hazell
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1511 –1516
 DOI: 10.1049/piee.1971.0277
 Type: Article
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By considering the solution of the differential equation governing the current delivered, via a thyristor bridge, to a series RL load, an exact nonlinear difference equation relating the current at consecutive firing instants is established. The behaviour of the system, both statically and dynamically, is thereby examined and use is made of transitionmapping concepts. Perturbational analysis is performed to linearise the equation and it is demonstrated that the system can be considered as a discrete controller with proportional and derivative control having a varying time constant. Computer simulation and experimental results are presented as evidence of the validity of the developed models.
Numerical inversion of the Laplace transform using generalised Laguerre polynomials
 Author(s): R. Piessens and M.A. Maria branders
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1517 –1522
 DOI: 10.1049/piee.1971.0278
 Type: Article
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The calculation of the transient response corresponding to a given frequency response is a problem of numerical inversion of a Laplace transform. Two methods are presented: a very economical method, which is suitable only for a limited class of Laplace transforms, and a general method. FORTRAN programs for both methods are described. The general method is compared with other general methods.
Characteristics of impulse breakdown of standard rod gaps under controlledatmosphere conditions
 Author(s): J.E. Matthews and R. SaintArnaud
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1524 –1527
 DOI: 10.1049/piee.1971.0279
 Type: Article
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The effect of humidity, polarity and irradiation on the 1/50μs impulse voltage breakdown and time lag of standard rod gaps has been determined for a range of spacings from 5cm to 30cm and a range of humidities from 1g/m^{3} to 24g/m^{3}. An anomalous condition is reported for a 5cm unirradiated gap under positive impulses in which the slope of the humidity characteristic is opposite to that normally obtained. It is shown that, although the time lag is independent of humidity, the probability of breakdown in the sigmoid region is not independent of humidity.
Prebreakdown phenomena in standard rod gaps subjected to impulse voltages
 Author(s): J.E. Matthews and R. SaintArnaud
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1528 –1534
 DOI: 10.1049/piee.1971.0280
 Type: Article
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The prebreakdown phenomena of impulse corona, corona propagation and leader propagation in the standard rod gap in air have been studied for spacings of up to 30 cm. The variations occurring in the measured quantities of coronacurrent amplitude, time of occurrence, coronapropagation time, corona speed, number and length of steps in the leaders, leaderpropagation time and leader speed are correlated to the variations in the conditions of gap length, applied voltage, humidity and irradiation. The results of the prebreakdown phenomena have been shown to explain the characteristics of impulse breakdown of the rod gap.
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