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1887

Proceedings of the Institution of Electrical Engineers

Volume 113, Issue 12, December 1966

Volumes & issues:

Volume 113, Issue 12

December 1966

Dependence of ionospheric absorption on solar zenith angle
Field distribution at bends in circular H0n and cylindrical surface waveguides
Radiation conductance of a slot covered with anisotropic plasma
  • Author(s): Gilbert H. Owyang  and  S.R. Seshadri
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 1920 –1926
  • DOI:  10.1049/piee.1966.0333
  • Type: Article
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  • p. 1920 –1926 (7)
    The radiation characteristics of an infinitesimal slot situated on an infinite perfectly conducting ground plane and covered by an anisotropic plasma layer are investigated, for the case of the magnetostatic field parallel to the ground plane but perpendicular to the slot. The radiation conductance of the slot contributed by the space waves and the power pattern are evaluated, and their dependence on the thickness of the plasma sheath, the signal frequency, the strength of the magnetostatic field and the effective collision frequency is examined. It is found that a suitable application of a static magnetic field increases the radiation conductance and the power pattern, for practically all directions, and these improvements are obtained even though the static magnetic field is not strong enough to render the plasma transparent for any direction of propagation.
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Power flow from a plasma having complex electroacoustic-wave impedance
  • Author(s): Robert L. Gallawa
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 1927 –1933
  • DOI:  10.1049/piee.1966.0334
  • Type: Article
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  • p. 1927 –1933 (7)
    The complex electroacoustic-wave impedance is examined and is related to power coupling at a plasma-vacuum boundary via the planewave solution of Maxwell's equations. The reactive component of impedance, which is due to the inclusion of a nonzero collision frequency, is found to be important at frequencies less than the plasma frequency, where it contributes a significant amount to power flow. Thus, at those frequencies, serious errors can be introduced by assuming that the electroacoustic power is made up of the powers in the incident and reflected waves only.
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Effect of multipath propagation on performance of narrowband frequency-modulation radiotelegraph systems
  • Author(s): K. Groves  and  P.N. Ridout
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 1934 –1942
  • DOI:  10.1049/piee.1966.0335
  • Type: Article
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  • p. 1934 –1942 (9)
    An explanation is given of the high error rate and poor diversity action experienced with narrowband frequency-modulation radiotelegraph systems with fading multipath signals, even in the absence of noise. The mechanism of occurrence of these residual errors is examined in detail, and they are shown to be due to a combined effect of the frequency modulation and spurious amplitude modulation of the signal, which together cause severe phase aberrations during the signal transitions at troughs in the fading. The spurious amplitude modulation is due to the removal of the higher-order frequency-modulation sidebands by the normal channel filters, and it is shown that a useful reduction in the residual-error rate and improved diversity operation may be achieved if the second-order sidebands reach the output of the channel-receiving filter at their correct level. A method of establishing this condition in a multichannel system with practical filters is described, but it is concluded that some increase in channel spacing in relation to modulation rate would be necessary to restrict interchannel interference.
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Theory and performance of a static magnetostrictive delay-line store
Parametric refrigeration of a transverse-wave tube
Physical limitations on the size of superconducting power transformers
  • Author(s): P.H. Borcherds
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 1953 –1956
  • DOI:  10.1049/piee.1966.0338
  • Type: Article
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  • p. 1953 –1956 (4)
    The volume of a superconducting transformer is calculated by investigating the behaviour of an idealised, lossfree, interleaved transformer. Because of the limitation of leakage magnetic fields with superconducting windings, it is found that the volume is large compared with a conventional transformer of the same power rating. It is shown how the volume of an idealised transformer can be reduced. When account is taken of the additional factors involved in designing a real superconducting transformer, it seems very probable that its size will be so much larger than that of an equivalent conventional transformer as to be unacceptable.
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A.C. diesel–electric drive system using consequential pole changing
  • Author(s): F.C. Williams ; J.F. Eastham ; D. Tipping ; G.W. McLean
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 1957 –1963
  • DOI:  10.1049/piee.1966.0339
  • Type: Article
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  • p. 1957 –1963 (7)
    The paper describes the development of a commutatorless diesel-electric drive system which uses an alternator and induction motors as the drive elements. The system provides a set of discrete final motor drive speeds at a fixed alternator drive speed, and so may be regarded as an electrical ‘gearbox’, a feature of the scheme being that, during normal operation, gear selection is carried out by pole changing the alternator excitation winding.Pole changing of the alternator output winding and the induction-motor stator winding is also used, but is a consequence of changing the alternator excitation pole number, and switching at full power level between the alternator and motors is thereby entirely avoided.The paper includes a sample design for a traction system having a continuous rating of 3600hp. The prediction of the performance of the sample design is substantiated by experimental results taken on a simplified laboratory model of the system.
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Development and design of windings to produce 2N pole settings
Discussion on “Interlocking in large electricity-supply substations—a fundamental approach”
Automatic resynchronisation of synchronous machines
Study of asynchronous operation and resynchronisation of synchronous machines by mathematical models
  • Author(s): O.P. Malik  and  B.J. Cory
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 1977 –1990
  • DOI:  10.1049/piee.1966.0343
  • Type: Article
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  • p. 1977 –1990 (14)
    The paper describes two mathematical models for the simulation of laminated-and solid-rotor synchronous machines. Employing these models, machine behaviour during asynchronous operation and the process of resynchronisation have been studied in detail using a general-purpose analogue computer. Results obtained on the analogue computer have been verified by comparison with results obtained on large alternators and on laboratory micromachines. Investigations have been made into the process of pulling into step from the state of steady asynchronous operation, using an entirely different approach, and the process is explained in simple physical terms. The effects of various auxiliary equipments, different machine parameters and system conditions on out-of-synchronous operation and resynchronisation have been studied.
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Discussion on “Induced voltages in the sheaths of crossbonded a.c. cables”
Corrigendum: Induced voltages in the sheaths of crossbonded a.c. cables
Determination of load losses and torques in squirrel-cage induction motors
  • Author(s): N. Christofides  and  B. Adkins
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 1995 –2005
  • DOI:  10.1049/piee.1966.0346
  • Type: Article
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  • p. 1995 –2005 (11)
    The load losses of an induction motor, defined as the difference between the actual losses and the conventional segregated losses under normal running conditions, have, in the past been difficult either to measure or to calculate accurately. An earlier paper gave methods of determining similar losses at larger slips and at reduced voltage, in terms of calculations and measurements of the torque/speed curve. The calculations allowed for saturation in the tooth tips, but not for saturation due to the full main flux which is present at normal voltage. The measurements were not made at full voltage because of heating considerations, and no useful measurements at normal full load were obtained because the load losses are a very small fraction of the input. In this paper, the method of calculation is modified, and improved testing methods are used to overcome these limitations, and thus to derive more reliable methods of measuring and calculating the load losses. Apparatus is described for the automatic recording of speed/torque and power-input curves at full voltage, from which the harmonic torques caused by the load losses can immediately be measured. The paper also describes a new back-to-back test for induction motors, which constitutes the most accurate and reliable method of measuring load losses under full-load conditions to date. Ten different rotors with carefully controlled parameters, used in conjunction with two identical stators, were tested in the back-to-back arrangement, and the results are compared with the theoretical computations and with the reverse-rotation test carried out on the same machines.
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Discussion on “Live washing of h.v. insulators in polluted areas” and “Surface coatings for h.v. insulators in polluted areas”
Corrigendum: Live washing of h.v. insulators in polluted areas
Solution of network transients using symmetrical-component techniques
Discussion on “The 250 kV d.c. submarine power-cable interconnection between the North and South Islands of New Zealand”
Transient analysis of power line/cable systems. Including reactive terminations with surge diverters
  • Author(s): J.H. Anderson  and  A.G. Heaton
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 2017 –2022
  • DOI:  10.1049/piee.1966.0351
  • Type: Article
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  • p. 2017 –2022 (6)
    Fault-limiting inductors have been found to be the cause of flashover on certain transmission systems, and the proposal to employ them on projected installations therefore raises the question of the magnitude of the transient overvoltages to be expected when the system is energised by various switching arrangements. The paper presents the results of digital-computer studies on a number of systems, existing and proposed, and it is shown that, where flashover has occurred, this could have been predicted at the design stage. The computer program developed for these studies is quite general, and will deal with any cascade combination of lines and cables, as well as allowing for precharge on the line and the nonlinear characteristics of a surge diverter if sparkover occurs. It is also indicated how a closed form of solution may be obtained from a knowledge of the eigenvalues and eigenvectors of the system matrix, and how the contributions of the separate modes to the overall response may be isolated.
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Stator flux distributions in Lorenz-type medium-frequency inductor alternators
  • Author(s): E.J. Davies  and  R.K. Lay
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 2023 –2030
  • DOI:  10.1049/piee.1966.0352
  • Type: Article
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  • p. 2023 –2030 (8)
    This theoretical and experimental analysis of the magnitudes and distribution of stator-flux harmonic components in a Lorenz-type inductor alternator is part of a broad investigation into this class of machine. The test alternator is a specially designed 30kW model of the standard 300kW industrial unit. Current designs employ field damping to reduce second-harmonic flux modulations expected by analogy with the Guy-type inductor alternator on load. The paper shows that no modulation of the field flux could exist in an ideal Lorenz-type alternator. However, the practical machine, with a.c.-slot openings interrupting the stator surface between field slots, will have harmonic components of flux, both on open circuit and on load, whose magnitudes depend on the width of the a.c.-slot opening. Damping is shown to be sucessful in reducing second- (and other even-) harmonic components, whilst being totally ineffective against fundamental variations in field flux and odd-order-harmonic fluxes. A theory is given that explains these effects. Measurements on the experimental model verify this theory. The paper introduces a technique for relating fluxes to the geometry of the airgap surfaces, and has shown the distribution for inductor alternators to be somewhat more complex than was presumed. It is expected that this analysis will solve the problem of accurate loss calculation in these machines.
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Method of rapidly reversing large currents in highly inductive loads
Note on transformation under power invariance
  • Author(s): M.R. Harris  and  K.H. Low
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 2035 –2037
  • DOI:  10.1049/piee.1966.0354
  • Type: Article
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  • p. 2035 –2037 (3)
    The voltage transformation, corresponding to a current transformation i = C.i′, is usually taken as v′=Ct,.v, for invariance of total instantaneous power. It is shown that this solution is not unique, but is one of an infinite family, having the general formv′=[I+Zs.Z′0−1].Ctvwhere Zs is any skew-symmetric nonreactive impedance matrix, and Z′0 is the usual transformed impedance matrix. The theory of this matter is outlined, and its topological significance (corresponding to interconnection with gyrators) is discussed. All the usual properties of invariance apply to this more general solution. Whilst this treatment clarifies a mathematical difficulty, the extended solutions are not apparently of great physical importance.
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Sinewave thyristor parallel invertor with improved commutation
Testing and approval of electrical appliances
Discussion on “Dynamic model studies of overhead equipment for electric railway traction” and “Pantograph motion on a nearly uniform railway overhead line”
Axially laminated anisotropic rotors for reluctance motors
High-speed analogue–digital convertor
  • Author(s): D.J. Kinniment ; D. Aspinall ; D.B.G. Edwards
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 2061 –2069
  • DOI:  10.1049/piee.1966.0359
  • Type: Article
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  • p. 2061 –2069 (9)
    The conversion time of fast analogue-digital convertors which use the successive-approximation conversion method is usually limited by the time the discriminator takes to respond with the required accuracy. The ratio of discriminator overload to required accuracy for any particular operation can be improved by the use of an error-correction system. This improvement has been exploited to obtain a faster response time from the discriminator, and a 7-bit convertor has been constructed which achieves a sampling rate of 9 Mc/s. The convertor speed is twice that which could be obtained from its Goto-pair tunnel-diode discriminator in a less complex successive-approximation system.
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Barrier method of ensuring the safety of electrical circuits in explosive atmospheres
  • Author(s): R.J. Redding  and  L.C. Towle
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 2070 –2074
  • DOI:  10.1049/piee.1966.0360
  • Type: Article
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  • p. 2070 –2074 (5)
    Two techniques—flameproofing and intrinsic safety—have been regularly employed to meet safety regulations for dangerous atmospheres. Certification has been based on representative tests on sample equipment. In the case of instrumentation and control equipment, the complexity of modern electronic equipment makes testing onerous, complicated and time consuming. An entirely new method is based on the use of an electrical barrier placed at the boundary between the safe and hazardous areas to ensure that the energy entering the hazardous area cannot approach, by a large margin of safety, the level at which ignition occurs. A barrier device applicable to electrical process-control circuits using d.c. signals is described. The philosophy behind the design of the unit, its physical construction and method of application, and the limitations it imposes are detailed. Further designs for similar purposes are outlined, but the method is limited to circuits where the power does not exceed a few watts. The barrier comprises a network of resistors and semiconductor diodes chosen to have negligible effect at normal signal levels. The diodes conduct during fault conditions, and we need only consider the worst case, namely, the direct application of the power mains to the protected circuit. The maximum energy which can enter the hazardous area is defined, and the degree of safety can be determined by inspection of the components in the danger area.
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Statistical properties of a class of pseudorandom sequences
  • Author(s): H.R. Simpson
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 2075 –2080
  • DOI:  10.1049/piee.1966.0361
  • Type: Article
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  • p. 2075 –2080 (6)
    The class of sequences discussed in the paper consists of those sequences which can be produced by inversion of alternate values in binary maximal-length sequences. The statistical properties of such sequences are analysed in terms of their multidimensional higher-order autocorrelation functions, and the results are compared with the statistical properties of a truly random binary sequence. The odd-order autocorrelation functions are identically zero. Some general properties of the even-order autocorrelation functions are derived. A sampled-data Laguerre filter chain is used to assess the statistical properties of some typical sequences. The paper ends with a discussion of some techniques which can be used to form multilevel sequences.
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Method of statistical linearisation. Its application for evaluation of the response of a hysteretic system to Gaussian inputs
  • Author(s): A.K. Nath  and  A.K. Mahalanabis
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 2081 –2086
  • DOI:  10.1049/piee.1966.0362
  • Type: Article
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  • p. 2081 –2086 (6)
    The paper describes a method of computing the statistical equivalent gain of a nonlinear element in the minimum r.m.s. error sense. The method is based on the facts that:(a) A band-limited Gaussian signal x(t) can be expressed asx(t)=R(t) cos (ωmt+θ)where ωm is the midband frequency, and R and θ are independent random variables.(b) Ranges of these two variables are (0, ∞) and (0, 2π), respectively.(c) Angle θ has uniform distribution, while R obeys a definite distribution law obtainable from the known distribution law for x(t).The method has the advantage that it is equally well applicable to single- and double-valued nonlinearities. This is illustrated by working out the equivalent gains of a number of well known nonlinear characteristics. Finally, the error-response characteristics of a hysteretic system under excitation from a Gaussian random signal are analysed by using the equivalent gain obtained in the paper. These analytical data are checked against simulated results.
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Magnetisation of isotropic and ferromagnetic conducting media
  • Author(s): V. Bunea
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 2087 –2094
  • DOI:  10.1049/piee.1966.0363
  • Type: Article
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  • p. 2087 –2094 (8)
    The main object of the paper is to present a new method for the exact and complete solution of the field-distribution problem of a.c. magnetisation of saturated ferromagnetic media, with or without hysteresis. The technique of ‘continuous time-discrete space equations’ has been applied. The waveforms of the flux density in different layers and of the boundary field, for magnetisation with total sinusoidal flux of thin iron laminations, are shown. The method may be extended to the magnetisation of cylindrical iron conductors with circular sections or to a ferromagnetic halfspace. The method has been applied first to the a.c. magnetisation of linear isotropic conducting media. The ‘continuous time-discrete space-equations’ technique applied in that case allows us to write, as a function of the contour form, the analytical equations which give the field distribution for any cylindrical conductor. Relations giving the flux-density distribution in thin laminations and in bars with flat rectangular sections are established.
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Discussion on “Distribution of mechanical forces in magnetised material” and “Evaluation of magnetic energy density in magnetised matter”
Tarantula—100 kV pinch discharge apparatus for studying shock waves
  • Author(s): W.R. Bell ; A.E. Bishop ; H.J. Crawley ; G.D. Edmonds ; J.W.M. Paul ; J. Sheffield
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 2099 –2106
  • DOI:  10.1049/piee.1966.0365
  • Type: Article
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  • p. 2099 –2106 (8)
    An experimental apparatus for research on powerful shock waves in a plasma is described. The shock waves are produced by the cylindrical compression of a plasma by the pinch effect. The experiment is performed in a fused-silica discharge tube im long by 0.5 m bore. An initial axial magnetic field of up to 0.5 Wb/m2 is provided. A low-pressure gas in the tube is preionised by using various capacitor discharge circuits. A high voltage is then applied inductively between the end electrodes of the tube from a low- inductance circuit. This circuit, which stores up to 100 kJ at 100 kV, is switched by 40 spark gaps and can deliver up to 1 MA with a peak of dI/dt of 2.5 TA/s. These high currents generate large impulsive forces which, without care, could damage the fragile silica tube. This tube is held in place by silicone rubber which also provides the main insulation.The design and operation of the apparatus are described with particular emphasis on the two major problems encountered: (a) switching the 100 kV circuit and (b) providing insulation and support for the silica tube.
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Design and operation of the battery power supply of a hypersonic-propulsion facility
  • Author(s): E.A. Bunt ; R.T. Cusick ; L.W. Bennett ; H.L. Olsen
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 12, p. 2107 –2113
  • DOI:  10.1049/piee.1966.0366
  • Type: Article
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  • p. 2107 –2113 (7)
    A power supply composed of 1140 submarine lead-acid cells for operating split-ring plasma-arc heaters is briefly described, and its application to flight simulation is reviewed. Heavy current requirements lead to battery loading up to the limit imposed by the onset of the voltage-reversal phenomenon; the additional effect of circuit transients on arc stability is also discussed. Control equipment includes a water-cooled ballast resistor and separate switches to handle making and breaking functions. Remote operation ensures the basic safety of personnel.
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Discussion on “Discharge detection and measurements”
Measurement of the stability of an electric arc
Distribution of ionisation in discharge gaps irradiated with radioactive material

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