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1887

Proceedings of the Institution of Electrical Engineers

Volume 113, Issue 6, June 1966

Volumes & issues:

Volume 113, Issue 6

June 1966

Spectral-noise characteristics of glow discharges in the frequency range 1kc/s–8Mc/s
  • Author(s): K. Barker  and  F.A. Benson
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 937 –942
  • DOI:  10.1049/piee.1966.0156
  • Type: Article
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  • p. 937 –942 (6)
    Measurements of the small-signal impedance and noise voltage have been made over the frequency range 1 kc/s to 8 Mc/s for glow-discharge tubes filled with pure neon at pressures from 10 to 60torr. The equivalent circuits of the discharge with respect to the impedance and noise are shown, and the spectral variations of noise voltage and current are explained with reference to them. The relationship between the noise-current spectrum and the convection-current admittance is also given. It has been found that the high-frequency white-noise current from the gas tube is not the same as the shot noise in a temperature-limited diode carrying the same tube current.
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Design of wide-range varactor-tuned microwave tunnel-diode oscillators
  • Author(s): D. Cawsey
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 943 –947
  • DOI:  10.1049/piee.1966.0157
  • Type: Article
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  • p. 943 –947 (5)
    The paper describes the application of tunnel diodes to electronically tunable microwave oscillators. The properties of tunnel diodes are described, and oscillators with a wide tuning range are considered in detail. In order to achieve frequency stability, the tunnel diode should be weakly coupled to a relatively high-Q factor resonator, and this principle is applied to the design of electronically tuned oscillators using varactor diodes as tuning elements. Some comparisons are made with mechanically tuned oscillators designed according to similar principles. The form of construction is described and some results are discussed.
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Application of the magnetoresistance effect in semiconductors to microwave power measurements
  • Author(s): S. Kataoka
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 948 –956
  • DOI:  10.1049/piee.1966.0158
  • Type: Article
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  • p. 948 –956 (9)
    Theoretical and experimental investigations have been made on the application of the magnetoresistance effect in semiconductors to the measurement of microwave power. Five magnetoresistance microwave wattmeters of different kinds, with InSb or InAs elements, were constructed. Various measurements were taken, at 10 or 34Gc/s, to investigate the existence of the multiplying action between the electric- and magnetic-field components of the wave by the magnetoresistance effect, varying the magnitude and phase of the current through the element by means of an adjustable coaxial piston.All the measurements showed a qualitative agreement with theory. A direct voltage output across the element, resulting from the multiplying action of the magnetoresistance effect, was observed for each wattmeter, and, when suitable phasing adjustments had been made, was found to bear a good linear relationship to the microwave power in the guide, reversing its polarity with a reversal of the direction of the bias magnetic field.
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Braid construction and attenuation of coaxial cables at microwave frequencies
  • Author(s): J.L. Goldberg  and  R.J. Slaughter
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 957 –962
  • DOI:  10.1049/piee.1966.0159
  • Type: Article
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  • p. 957 –962 (6)
    The attenuation performance of flexible coaxial cables in the microwave region has been measured for a number of different braid designs in order to elucidate the phenomenon of attenuation instability and to achieve a design for a cable of predictable performance.The variables investigated were braid-wire size and tension, braid angle and filling factor, type of weave, and, for the first time, gold plating as an alternative surface finish to the usual silver plating.A simplified theoretical treatment is given in support of the previously held view that attenuation instability results from dissipation of energy in the contact resistances between braid wires, and order-of-magnitude agreement is obtained with measured values.Aging tests for up to 8000h at 85°C showed that, for cables which are not subjected to flexing in service, the best performance is given by a short-lay gold-plated copper-wire braid of adequate tension. Silver plating is preferable in cables where flexing is adequate to clean the contacts between braid wires.
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Measuring methods for r.f. cables in the u.h.f. range
  • Author(s): H. Peters  and  Th. Fischer
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 963 –969
  • DOI:  10.1049/piee.1966.0160
  • Type: Article
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  • p. 963 –969 (7)
    The paper deals with methods of measurement employed to ascertain the special characteristics of r.f. cables in the frequency range 470–960Mc/s. In the first part, general methods are described for determining the mean characteristic impedance, attenuation and power-handling capacity, and dielectric strength and screening efficiency are also discussed.The second part of the paper deals with methods for equalising the electrical lengths of the two feeder cables in split-aerial systems. The choice of the measuring methods has been determined primarily by the consideration that nonuniformity of the feeders must not interfere with the accuracy of the results. Next, a method is described for the continuous measurement of the v.s.w.r. in the operating frequency range. A sufficiently low value of v.s.w.r. must be ensured, as otherwise inadmissible distortion would occur in the filter curve of the diplexer installed between transmitter and cable. In addition, a measuring method is discussed which operates with a pulse modulated on a carrier frequency. The halfpulse duration is approximately 0.1 μ, equal to the duration of the image point. The carrier frequency is adjustable within the operating frequency range. Local reflections in the cable, which might distort the video signal, become apparent by this method.Finally, a method is presented for measuring the characteristics of cable connectors, and for compensating for any possible mismatches at the joints between cable and connectors.Results are given of the measurements obtained for feeder cables installed in the United Kingdom, using the methods referred to. These give some indication of the quality of the feeder cables obtainable at the present time for use in the u.h.f. range.
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Cascade connection for time-invariant n-port networks
  • Author(s): B.D.O. Anderson  and  R.W. Newcomb
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 970 –974
  • DOI:  10.1049/piee.1966.0161
  • Type: Article
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  • p. 970 –974 (5)
    Questions concerning the existence of the scattering matrix for the interconnection of two networks are considered. It is shown that all interconnections can be regarded as a special type of interconnection termed cascade loading. If two networks in the cascade-loading configuration are separately linear, passive, time-invariant and have scattering matrixes, the same is true of the interconnection network. This result is applied to finite networks, and it is shown that any finite network composed of passive resistors, capacitors, inductors, gyrators and transformers has a scattering matrix. Some illustrative examples are also considered, pointing out that the results stated are the best obtainable.
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Synthesis of LC networks—a state-model approach
Canonic LC equivalent network transformations
Field-store standards conversion: Conversion between television signals with different field frequencies using ultrasonic delays
  • Author(s): W. Wharton  and  R.E. Davies
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 989 –996
  • DOI:  10.1049/piee.1966.0164
  • Type: Article
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  • p. 989 –996 (8)
    At the present time, standards conversion between television signals having different field frequencies is carried out by the image transfer method. This method results in a significant impairment of picture quality, and the convertors used require considerable maintenance and adjustment. In this paper, new methods of conversion are discussed which should overcome these disadvantages. The convertors proposed use fused-quartz ultrasonic delays capable of storing a complete field at the input standard and can be conveniently termed field-store convertors.
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Experimental study of the theory of optical superheterodyne reception
  • Author(s): M.P. Warden
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 997 –1004
  • DOI:  10.1049/piee.1966.0165
  • Type: Article
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  • p. 997 –1004 (8)
    A theoretical expression for the power signal/noise ratio obtained with an optical superheterodyne receiver is presented, and practical departures from it are discussed. A modification to this expression, proposed by an author using photon-fluctuation theory, is considered. A detailed description is given of the experimental equipment used in the study of the theoretical predictions. A helium-neon gas laser, stabilised in amplitude and frequency to give single-axial-mode operation, was used both as a source and a local oscillator, a moving prism giving the required frequency shift. A photomultiplier was used as the photomixer. The experimental results are in very close agreement with theory.
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Current transformers with capacitive burdens
  • Author(s): A. Wright
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1005 –1015
  • DOI:  10.1049/piee.1966.0166
  • Type: Article
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  • p. 1005 –1015 (11)
    Capacitors may be included in the secondary circuits of current transformers, to effect filtering or tuning or to compensate for the capacitance of equipment being protected. While, in the past, considerable attention has been given to the behaviour of current transformers feeding resistive and inductive burdens, very little has been given to the performance obtained when there are capacitors in the burden. This paper is devoted to this purpose. Initially, the steady-state behaviour obtained when a sinusoidal current is flowing in the transformer primary winding is examined, with both purely capacitive and series RC burdens connected to the secondary winding. The types of output obtained when core saturation occurs, and the core-flux saturation levels needed to avoid saturation, are determined. The interesting feature revealed is that it is possible, under certain conditions, to have three possible secondary currents for a given primary current, with fixed circuit parameters. This effect is due to ferroresonance, and it is clearly important, as it could seriously affect the performance of associated protective equipment. The later part of the paper deals with the behaviour, during transient conditions on the system, of transformers with capacitive burdens. It is shown that the presence of capacitance in the burden of a transformer causes its core flux to contain a component which changes linearly with time. Such a component causes the inevitable onset of saturation in the event of a system fault which persists for a few cycles, and thus it makes it impossible to design transformers which should be suitable for protective equipment such as that used in association with busbars.
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Analysis of doubly fed slip-ring machines
  • Author(s): B.M. Bird  and  R.F. Burbidge
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1016 –1020
  • DOI:  10.1049/piee.1966.0167
  • Type: Article
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  • p. 1016 –1020 (5)
    It is shown that a broad class of machines exists whose members may be regarded as doubly fed slip-ring machines. The paper presents a simple approach to the analysis of the steady-state performance of such machines, and indicates the interrelation between a number of conventional machines and other less orthodox machines. In particular, the double-speed doubly fed machine is examined in some detail, and it is shown theoretically that the peak-power capability of this machine when acting as a motor is greater than that of any comparable form of machine.
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Effect of excitation regulation on synchronous-machine stability
  • Author(s): L.J. Jacovides  and  B. Adkins
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1021 –1034
  • DOI:  10.1049/piee.1966.0168
  • Type: Article
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  • p. 1021 –1034 (14)
    The paper records a detailed study of the effect of a voltage regulator on the stability of an alternator connected through a reactance to an infinite bus. The stability is analysed by means of Nyquist loci calculated for the transfer functions of alternator and regulator. The accuracy and speed of response of the system are also considered. The first part of the paper considers a simple regulator with proportional feedback, and it is shown that such an ideal regulator can extend the region of steady-state stability to a point corresponding to the maximum of the transient power-angle curve.Practical regulators are classified according to the nature of their transfer functions. The analysis provides a means of predicting their behaviour and explains how they affect the stability, accuracy and response. The effect of delay elements, integrator elements and derivative elements in the regulator is considered particularly; e.g. a buck-boost exciter, which effectively introduces an integrator element, gives good accuracy but less satisfactory response, and has a limited effect on stability, and a derivative regulator which gives rapid response and a large extension of the stability region, but has limited accuracy.Experiments performed on a model machine with various simulated regulators agreed well with the computed results. The computations allowed fully for the system parameters, including alternator resistance and alternator damping.
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Influence of transient switching currents and fluxes on the torque developed by a squirrel-cage induction motor
  • Author(s): N.C. Enslin ; W.M. Kaplan ; J.L. Davies
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1035 –1043
  • DOI:  10.1049/piee.1966.0169
  • Type: Article
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  • p. 1035 –1043 (9)
    Theoretical expressions for the instantaneous torque as a function of time are given in terms of the motor constants, its speed and the conditions of simultaneous stator switching.Calculated torque/time curves are shown superimposed on experimental oscillograrns. The correlation in phase, frequency of pulsation and decrement verifies the theoretical analysis, though there is a discrepancy in amplitude for slips greater than 1.0. This difference also exists between the calculated and experimental steady-state torques.It is shown that the transient components carried by the rotor have a longer duration than those due to the stator. The former therefore predominate and produce torque pulsations at a frequency slightly less than slip frequency, except at standstill when this difference disappears. The frequency departure is governed by the short-circuit constants of the motor, particularly the ratio of leakage reactance to resistance of the windings. The stator-borne transients produce torques which last for about one cycle of the supply for the machine investigated, and have a frequency departing slightly from (1−s)f.The time constant of the rotor-produced transients is a maximum at standstill and decreases symmetrically to approximately 10% of the standstill value for slips of 2.0 and 0. The time constant of the stator-produced transient does not vary by more than 30% for slips from 0 to 2.0. The torque components are tabulated with their corresponding frequencies and amplitude decrements.
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Linear induction motors for low-speed and standstill application
  • Author(s): G.F. Nix  and  E.R. Laithwaite
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1044 –1056
  • DOI:  10.1049/piee.1966.0170
  • Type: Article
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  • p. 1044 –1056 (13)
    Devices which are required to produce force with virtually no movement have zero power output. The effectiveness of such devices cannot therefore be assessed in terms of their efficiency or power/weight ratio. Quantities which are important in the design of force-producing machines or ‘actuators’ are the force/input, force/weight and force/cost ratios and similar quantities. Reliability is also often a potent factor. The paper examines the use of linear motors as actuators under these criteria and formulates design procedure. The optimisation of the force/input ratio for a machine whose speed is not zero, but low in comparison to that of conventional machines, is carried out with the aid of a computer program. Considerable simplification of manufacture is achieved by the use of the tubular or axial-flux form of construction. Forces in linear motors of both transverse and axial-flux types are calculated, taking end effects into account. The design of an existing commercially produced tubular actuator is discussed.
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Study of symmetrical and related components through the theory of linear vector spaces
  • Author(s): N. Dharma Rao  and  H.N. Ramachandra Rao
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1057 –1062
  • DOI:  10.1049/piee.1966.0171
  • Type: Article
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  • p. 1057 –1062 (6)
    The paper proposes a study of symmetrical and related components, based on the theory of linear vector spaces. Using the concept of equivalence, the transformation matrixes of Clarke, Kimbark, Concordia, Boyajian and Koga are shown to be column equivalent to Fortescue's symmetrical-component transformation matrix. With a constraint on power, criteria are presented for the choice of bases for voltage and current vector spaces. In particular, it is shown that, for power invariance, either the same orthonormal (self-reciprocal) basis must be chosen for both voltage and current vector spaces, or the basis of one must be chosen to be reciprocal to that of the other. The original α, β, 0 components of Clarke are modified to achieve power invariance. For machine analysis, it is shown that invariant transformations lead to reciprocal mutual inductances between the equivalent circuits. The relative merits of the various components are discussed.
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Interlocking in large electricity-supply substations—a fundamental approach
  • Author(s): G.P. Hutchinson
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1063 –1074
  • DOI:  10.1049/piee.1966.0172
  • Type: Article
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  • p. 1063 –1074 (12)
    The paper briefly reviews the interlocking of electrical plant and switchgear in large transmission substations, and shows that grouping occurs in two categories according to the switching function; i.e. whether for access and maintenance or operational purposes. There is a brief discussion of interlocking requirements and of conventional interlock principles using both mechanical-key and electrical-bolt arrangements.The philosophy of interlocking is considered against a background of system faults which have occurred, and the inadequacies of incomplete interlocking are discussed.The bulk of the paper is devoted to the development of a new approach to interlock circuit design, which is based on fundamental principles and uses established network theorems, and which is shown to be easily adaptable to any primary switching arrangement, however complicated.It is shown that, contrary to previous experience, when using the new principles, the interlocking of a substation need not place constraints upon the primary circuit design, such as has occurred in the past with conventional schemes. It is also shown that former unorthodox switching sequences which required the defeating of interlocks can be performed with the interlocks in full operation. Two schemes of interlocking, one using d.c. supply sources and one using a.c. sources are developed, and a practical scheme for a 4-switch-mesh substation, with mesh-opening isolators, is described.It is suggested that the new scheme makes possible the comprehensive interlocking of a substation as required for fully automatic switchgear operation, and that it has application in remote automatic-instructor mimic diagrams at control centres.
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Electrically heated multistorey-building analysis
Dynamics of the parameter-perturbation process
  • Author(s): J.L. Douce ; K.C. Ng ; M.M. Gupta
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1077 –1083
  • DOI:  10.1049/piee.1966.0174
  • Type: Article
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  • p. 1077 –1083 (7)
    It is shown how the mean-square error of a linear system varies with time following a small change in any parameter of the system. It has been assumed that the system is in the steady-state condition before the parameter perturbation is applied. The input signal to the system may be deterministic or a random process with known statistical properties. By considering the response to a step parameter change, a linear model is developed relating the change in the mean-square error (ensemble average) to the parameter variation. Further, the principle of superposition is shown to be applicable, so that the change in mean-square error for any arbitrary system input can be found when the behaviour is known for sinusoidal system input signals. Experimental and theoretical work is presented for particular systems.
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Sensitivity improvement using optimal design
Dynamic programming and synthesis of linear optimal control systems
Theorem on Stieltjes correlation
  • Author(s): G. The
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1091 –1094
  • DOI:  10.1049/piee.1966.0177
  • Type: Article
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  • p. 1091 –1094 (4)
    A theorem on Stieltjes correlation is formulated, in which it is shown that, in theory, Stieltjes correlation techniques do not produce any distortion of the true correlation function, provided that the two inputs are stationary, ergodic and have a normal joint distribution function. The errors due to finite averaging time are discussed, and it is shown that an analytical evaluation of the signal/noise ratio of a practical Stieltjes correlator requires knowledge of the autocorrelation function of the product function, which is dependent on the quantiser characteristics.
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Input-transducer errors in binary crosscorrelation experiments. Part 3
  • Author(s): K.R. Godfrey
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1095 –1102
  • DOI:  10.1049/piee.1966.0178
  • Type: Article
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  • p. 1095 –1102 (8)
    The crosscorrelation function between the output of an electrical network excited by an imperfect form j(t) of a pseudorandom binary signal i(t) has been determined for four different forms of j(t). The object of the experiments was to simulate the action of a system input transducer, which, because of its dynamic response, is unable to follow i(t) exactly. The effects of both reversible and nonreversible transition delays (of exponential form) have been examined, the measured results confirming previously reported theoretical expressions. In one of the experimental runs, the interstate transition time θ of the signal j(t) was considerably greater than the basic interval Δt of j(t). Although θ is apparently too large for the theory to be applicable in this case, it was found that a reasonably accurate estimate of the measured crosscorrelation functions could nevertheless be made using the theory.
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Investigation of the electrical breakdown of transformer oil in Skowronski's cup-sphere spark gap
  • Author(s): J. Crawley  and  L. Angerer
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1103 –1105
  • DOI:  10.1049/piee.1966.0179
  • Type: Article
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  • p. 1103 –1105 (3)
    The cup-sphere spark gap designed by Skowronski is used to check the effects of impurities and dispersed water on the breakdown of transformer oil. Several different filters, with porosities varying from 0.05 to 2μm, are used for filtering oil samples. Filtering through a sintered-glass filter with a porosity of 2μm does not affect the breakdown of the oil, but some improvement in oil properties is observed when sintered-glass filters with porosities of 1.5 and 0.8μm are used. Filtering through plastic filters with porosities of 0.4, 0.1 and 0.05μm results in considerable increase in breakdown stress for all gap settings, accompanied by significant changes in the breakdown-voltage/gap-setting characteristics. The values recorded are much greater than those obtained using Kok's formula for the size of remaining particles in the oil. The effect of dispersed water is also studied, using the same cell and a 1 mm gap setting. The presence of water greatly affects the breakdown stress, which drops from 406kV/cm for dry oil to 63kV/cm for oil containing 0.06% of water. It is also found that the effect of particles in dry oil is less pronounced than that in oil containing dispersed water. The results presented are in good agreement with those published by Skowronski, who used the same cell in his work.
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New system of spark-gap electrodes for measurement of dielectric strength of insulating liquids
Conduction currents in compressed methane
  • Author(s): B.W. Ward
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1109 –1112
  • DOI:  10.1049/piee.1966.0181
  • Type: Article
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  • p. 1109 –1112 (4)
    Conduction currents have been measured in compressed methane at pressures up to 12atm absolute. The standard Townsend method was used to determine Townsend's first ionisation coefficient α for values of E/p0 (electric stress/pressure corrected to 0°C) between 24.3 and 32.9 V/cm torr. This extends previous measurements to lower E/p0 and higher pressures.Field-emission currents were detected at the highest pressures, and an anomalous current, which does not follow a normal Townsend amplification law, was also observed following the electrical breakdown of the compressed gas. Suggestions for the origin of this anomalous current are given, and the contributions to breakdown of prebreakdown processes is discussed.
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Corona and breakdown-voltage characteristics in sphere—plane and rod—rod gaps under impulse voltages of various wavefront durations
  • Author(s): E. Kuffel ; M. Abdullah ; M. Abdullah
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1113 –1119
  • DOI:  10.1049/piee.1966.0182
  • Type: Article
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  • p. 1113 –1119 (7)
    Studies were made of the electrical characteristics of the corona and the leader stroke preceding the impulse breakdown of sphere—plane and rod—rod gaps up to 40cm long, in atmospheric air. The studies were made with both positive- and negative-polarity voltages of front durations between 2 and 300 μs. The effect of wavefront duration on the breakdown voltage was also studied.The breakdown voltage of the sphere—plane gap with the sphere positive, and of the rod—rod gap under both polarities, increased with increasing wavefront duration from 2 to 17 μs, and thereafter it decreased for wavefronts up to 300 μs. With the sphere negative, the breakdown voltage of the gaps studied remained approximately constant for all durations of the wavefronts.With the sphere positive, the breakdown of all gap lengths studied was preceded by the propagation of a positive leader. When the sphere was negative, however, a change in the development of the leader from a negative leader to a positive leader was observed at a certain gap length. The leader development remained independent of the wavefront duration of the voltage wave.The breakdown of the rod—rod gap with the high-voltage rod positive was initiated by a positive leader for all gap lengths and voltage wavefronts. With the high-voltage rod negative, two different mechanisms of the leader development were found under the 7 μs and 17 μs-wavefront voltages. In gaps between 10 and 20cm long, a positive leader was observed, whereas in the longer gaps the breakdown was initiated by a negative leader. Under the 2μs-wavefront voltage, the breakdown in all gaps was preceded by a positive leader.
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Approximate calculation of a complex 2-dimensional electric field
Nonlinear magnetisation in thin ferromagnetic plate
  • Author(s): V. Subba Rao
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 6, p. 1125 –1131
  • DOI:  10.1049/piee.1966.0184
  • Type: Article
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  • p. 1125 –1131 (7)
    In ferromagnetic circuits, a problem of interest is the predetermination of the time required for complete magnetisation of the material under impact excitation. The time of magnetisation gives an indication of the rapidity of response. Rigorous solutions of the problem are available in the literature for constant permeability and sections of simple geometry. For a nonlinear case of variable permeability, it is well known that an analytical description of the behaviour is extremely difficult. The problem of nonlinear magnetisation has applications in electrical machines, pulse transformers, magnetic memories and magnetic shift registers.The paper presents nonlinear analysis of the problem for a step m.m.f. excitation, using Maxwell's equations. For easy handling by practical design engineers, assumptions are made to obtain the final equations in a simple form. The results based on these equations are then compared with those of the painstaking graphical solution of the same problem. The favourable agreement justifies the assumptions made in obtaining the solution of the complex nonlinear problem. It is also shown in the paper that, for quick approximate computations, the author's previously reported equivalent circuit can be successfully used.
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Existing theories of operation of induction meters

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