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1887

Proceedings of the Institution of Electrical Engineers

Volume 115, Issue 4, April 1968

Volumes & issues:

Volume 115, Issue 4

April 1968

A fully electrostatic, flat, thin television tube
  • Author(s): D. Gabor ; H.A.W. Tothill ; Joyce E. Smith-Whittington
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 467 –478
  • DOI:  10.1049/piee.1968.0087
  • Type: Article
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  • p. 467 –478 (12)
    A description is given of important improvements and modifications which have been made in the design of a flat television tube. In the new form, magnetic components have been eliminated and considerable structural simplifications have been made. An electrostatic deflection system is described which is capable of giving deflection angles of ±60°, and a mathematical model of such a system is developed. The design of the electrostatic collimator which follows the deflection system is treated mathematically, and results of measurements on experimental models of both components of the tube are described. The action of the scanning array which provides the frame scan is discussed.
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Narrowband microwave suppression filters
  • Author(s): D.M. Kitching ; B.G. Bosch ; W.A. Gambling
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 479 –486
  • DOI:  10.1049/piee.1968.0088
  • Type: Article
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  • p. 479 –486 (8)
    A theoretical and experimental investigation into narrow-bandwidth microwave rejection filters, which can be constructed from simple, standard microwave components, is described. Suppression factors of at least 50dB at resonance are possible, and the bandwidth can be easily controlled. A simple form of analysis, which indicates clearly the effects of variation in the parameters, gives good agreement with experimental measurements. The possibility of using a 2-cavity system to obtain a slightly broader frequency response and a very low insertion loss, at the expense of a lower suppression factor at the centre frequency, is indicated.
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Saturation characteristics of tunnel-diode amplifiers
Noise in transistor mixers at high frequencies
  • Author(s): R.G. Meyer
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 487 –495
  • DOI:  10.1049/piee.1968.0090
  • Type: Article
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  • p. 487 –495 (9)
    The noise performance of transistor mixers at high frequencies is investigated by first considering the signal processes in the mixer. A knowledge of the mixer signal performance, and consideration of the various noise sources in the transistor, allows calculation of expressions for the mixer noise figure and optimum source resistance. The effects of variation in operating conditions are discussed, and, in particular, it is shown that, at very high frequencies, the mixer noise figure increases rapidly with collector current. Expressions for mixer and amplifier noise figure are compared and the basic differences are discussed.
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F.E.T. operation in the pinchoff mode
V.H.F. radio propagation by double-hop reflection from a tropospheric layer
  • Author(s): M.P.M. Hall
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 503 –506
  • DOI:  10.1049/piee.1968.0092
  • Type: Article
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  • p. 503 –506 (4)
    A propagation mechanism is discussed which comprises two reflections from a horizontally-stratified, partially-reflecting layer. Such a layer located appreciably below the ‘crossover height’ (i.e. the height of intersection of the horizon rays from the terminals) may cause an enhancement of signal strength which exceeds that obtained with a single reflection from a similar layer at the crossover height. This mechanism appears to give a satisfactory explanation for the experimental results obtained by Lane and Sollum in a study of layer-mode propagation over two radio paths, of length 139 and 309km, the shorter being over land and the longer partly over sea.
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Power-control characteristics of an asynchronised synchronous machine: a computer study
Prediction of induction-motor dynamic performance in power systems
  • Author(s): V.S. Ramsden ; N. Zorbas ; R.R. Booth
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 511 –518
  • DOI:  10.1049/piee.1968.0094
  • Type: Article
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  • p. 511 –518 (8)
    The application of the o-d-q transformation (due to Park) to the induction-machine equations is used to develop a set of equations suitable for use with a digital computer in the analysis of dynamic performance. The method of calculation is designed to be compatible with those already in use for the analysis of synchronous-machine behaviour and makes use of a novel equivalent circuit. An account is given of measurements taken on a range of laboratory motors to determine the variation of the principal parameters of the equivalent circuit with slip and voltage. A method of analysis is discussed which allows an adequate representation of an induction motor to be included in stability studies. The measured performance shows good agreement with that predicted using the computer program for the case where a small motor is fed from a larger machine which has lost synchronism, and an indication of the effect of neglecting some of the corrections is included.
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Transients in induction machines with terminal capacitors
  • Author(s): I.R. Smith  and  S. Sriharan
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 519 –527
  • DOI:  10.1049/piee.1968.0095
  • Type: Article
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  • p. 519 –527 (9)
    In order to study the influence of terminal capacitors on the transient behaviour of an induction machine, differential equations are developed in which the nonlinear effect of magnetic saturation is taken into account. Theoretical results obtained from a digital-computer solution of these equations are compared with experimental measurements on a 7.5hp motor. The transients investigated are those (a) following disconnection and reconnection to the supply with power-factor-correcting capacitors; (b) following disconnection and reconnection to the supply of the machine operated as a capacitor-excited induction generator; (c) during capacitor and magnetic braking of the motor.
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Voltage stability of radial power links
  • Author(s): B.M. Weedy  and  B.R. Cox
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 528 –536
  • DOI:  10.1049/piee.1968.0096
  • Type: Article
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  • p. 528 –536 (9)
    The general phenomenon of voltage collapse or instability at the load end of transmission links is introduced with reference to previous work, and the induction motor is seen to be the critical constituent of system loads. The power/voltage and reactive-power/voltage characteristics of power-system loads are predicted and accurately represented by polynomial expressions which are used in the analysis of radial transmission links fed from infinite busbars. Graphs summarising the critical load voltages and the corresponding short-circuit levels for various transformer tap ratios are given and are general in application; these are based on the dV/dZ criterion for voltage stability. It is shown that, although tap changing to raise the load voltage increases the critical length of the link, it also reduces the margin between normal operating voltage and the voltage at the onset of instability. The effects of the injection of reactive power by static capacitors are discussed, together with the effect of the induction-motor content of the loads. The use of the dEs/dVr criterion as advocated in the Russian literature is discussed.
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Back-to-back test for induction machines: floating gearbox
Universal winding for electrical-machine research
Unbalanced magnetic push
Decomposition techniques in power-system network load-flow analysis using the nodal-impedance matrix
Protection and stabilisation of large superconducting coils
  • Author(s): B.J. Maddock  and  G.B. James
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 543 –547
  • DOI:  10.1049/piee.1968.0101
  • Type: Article
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  • p. 543 –547 (5)
    Large superconducting coils, with stored energies from 108J upwards, must be stable and have a predictable performance. This is achieved by combining the superconductor with a good ordinary conductor (substrate) to form a composite and by providing cooling throughout the winding. In addition, large superconducting coils must be protected against overheating and voltage breakdown which might be caused by some failure, notably of the cooling system. We show that the use of an external resistor with a switch is a suitable method of protection and is preferable to the use of a secondary winding. A composite conductor is again the solution, and we show how to determine the minimum quantity of substrate which will satisfy the requirements both of stabilisation and of protection. We conclude that such large superconducting coils can be made stable and be protected.
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Rational-fraction approximations and asymptotic series
New electromagnetic suspension and its stabilisation
  • Author(s): B.V. Jayawant  and  D.P. Rea
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 549 –554
  • DOI:  10.1049/piee.1968.0103
  • Type: Article
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  • p. 549 –554 (6)
    The paper describes an electromagnetic suspension in which use is made of LCRcircuits to modify the force/distance characteristics between magnetised bodies. The modified characteristic is statically stable, and, although the use of series capacitance introduces Qfactor lag and oscillations, it is found by experiment that these can be damped out, giving a considerable advantage in power/weight ratio over the eddy-current method of levitation. It appears that analysis is possible by obtaining a transfer function between force of attraction and position, and an outline of the possible approach is given.
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End region of a single-load crossconnected m.h.d generator
  • Author(s): W.T. Norris  and  J.B. Heywood
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 555 –561
  • DOI:  10.1049/piee.1968.0104
  • Type: Article
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  • p. 555 –561 (7)
    A theoretical 2-dimensional analysis is made of the end region of a single-load crossconnected m.h.d. generator in which the duct cross-section, fluid properties and magnetic field are uniform, infinitely fine segmentation of the crossconnected electrode system is assumed. With a single load connected between solid electrodes at each end of the generator, the analysis predicts infinitely high current densities and electric fields at the junction of the solid-electrode and crossconnected sections. it is shown that these infinite concentrations can be removed by using grading resistors near the ends, and the design of one arrangement of grading resistors is discussed.
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Method of conjugate gradients applied to self-adaptive digital control systems
  • Author(s): R.H. Davis  and  P.D. Roberts
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 562 –571
  • DOI:  10.1049/piee.1968.0105
  • Type: Article
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  • p. 562 –571 (10)
    A simple continuous process is controlled by a digital computer. The process is initially identified and thereafter represented on a digital computer by means of a dynamic model. The optimum response of the model is obtained by adjusting the parameters of the digital controller to minimise a chosen cost function. Once the optimum controller has been determined by methods involving conjugate gradients, as compared to the method of steepest descent, the model is replaced by the actual process, which can then be controlled in an optimum fashion. It is possible for the computer to determine the model of the process and the optimum controller in an uninterrupted manner. The system is subjected to a step demand and a smoothed pseudorandom binary sequence.
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Optimal control of distributed-parameter systems
  • Author(s): M.M. Fahmy
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 572 –576
  • DOI:  10.1049/piee.1968.0106
  • Type: Article
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  • p. 572 –576 (5)
    The paper considers linear distributed-parameter systems described by the diffusion equation. A functional-analysis approach is used to develop a technique for obtaining explicit solutions to the class of optimum-control problems that are reducible to the abstract minimum-norm problem. To illustrate the technique, two specific problems are solved. In both cases, the initial state of the system is specified. In the first problem, it is required to find the spatially distributed control which drives the system to a specified terminal state at a specified terminal time, while minimising a generalised quadratic-performance index. In the second problem, the spatially distributed control is required to bring the system at a specified terminal time to a state which is closest to a specified state, while satisfying an inequality energy constraint.
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‘Circle criteria’ in the parameter plane
  • Author(s): J.B. Moore
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 577 –580
  • DOI:  10.1049/piee.1968.0107
  • Type: Article
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  • p. 577 –580 (4)
    The ‘circle criteria’ for giving stability information of linear systems containing one time-varying element are shown to have useful graphical interpretations for design purposes on a parameter-plane diagram. The significance of the parameter-plane approach is that, in a system design, the adjustable parameters of either the time-varying element or the time-invariant subsystem may be selected to satisfy the system stability constraints directly from the diagram. This means that for some design problems the parameter-plane approach is more efficient than the application of the well known complex-plane methods.
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Response of multidimensional nonlinearities to inputs which are separable processes
  • Author(s): R. Balasubramanian  and  D.P. Atherton
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 581 –590
  • DOI:  10.1049/piee.1968.0108
  • Type: Article
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  • p. 581 –590 (10)
    The property of separability of a process with respect to n random processes is defined and examples of such a process are given. The equivalent gains of a multidimensional nonlinearity (m.d.n.l.), obtained by Kazakov, are shown to constitute the best linear model of the m.d.n.l. in the Wiener sense if, and only if, each of the inputs is separable with respect to all the inputs. An extended version of Price's theorem is stated and proved, and its use in the determination of the output autocorrelation function for an m.d.n.l. is demonstrated. A series representation of the output autocorrelation function for an m.d.n.l. is also derived. The concepts of d.c. incremental gain and modified nonlinearity are extended to the multidimensional case, and their use in the analysis of closed-loop systems containing an m.d.n.l. is indicated. Finally, the applicability of these results to the general m.d.n.l. with n inputs and r outputs is demonstrated.
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Stability of nonlinear multivariable control systems
Automatic load scheduling in a multiarea power system
  • Author(s): T.P. Benthall
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 592 –596
  • DOI:  10.1049/piee.1968.0110
  • Type: Article
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  • p. 592 –596 (5)
    In the paper an algorithm is described for solving the problem of secure economic load scheduling on a large power system. The method is an extension of that of Wells, which solves the problem as a linear program by means of the dual simplex algorithm. A dual form of the decomposition principle of Dantzig and Wolfe is used in order to reduce the size of the problem, so that it can be solved efficiently on a computer system. This is correlated with a corresponding decomposition of the power system into autonomous areas, co-ordinated by the specification of recommended boundary transfers and spinning spare capacity. Further levels of decomposition are incorporated in a similar fashion, allowing three or more levels, say, for the CEGB supply system. Although the entire problem can be solved on a single computer, for application to online control a more complex computing system is anticipated.
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Digital-computer programs for an experimental automatic load-dispatching system
Automatic control of power-system frequency by machine controllers
  • Author(s): F. Moran  and  D.R. Williams
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 115, Issue 4, p. 606 –614
  • DOI:  10.1049/piee.1968.0112
  • Type: Article
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  • p. 606 –614 (9)
    The paper assesses the performance of the frequency-control loops of the machine controllers installed in the power stations participating in the automatic-load-scheduling experiment. It first describes the role of these control loops and explains the mechanism of frequency control, and then examines in detail the stability and performance of the machine-controller frequency loops. Included are results of extensive field tests carried out on both individual machines and isolated systems and of analogue-computer simulations. Stability and performance are shown to be closely dependent on the response characteristics of the conventional speed governors, as well as on the controller parameters.
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