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Volume 120
Issue 12
Proceedings of the Institution of Electrical Engineers
Volume 120, Issue 12, December 1973
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Volume 126 (1979)

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Volume 120 (1973)

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Volume 120, Issue 12
December 1973
Losses in braided coaxial cables in the frequency range 100 kHz–100 MHz
 Author(s): R.J. Teperek and F.A. Benson
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1465 –1468
 DOI: 10.1049/piee.1973.0302
 Type: Article
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The attenuation/frequency characteristics for three wirebraided coaxial cables and a tapebraided one in the frequency range 100 kHz to 100 MHz have been measured. The results are presented as braidingfactor/frequency curves, where braiding factor is defined as the ratio of the resistance of the braid to the resistance of an equivalent solid tubular outer conductor. The braiding factors are compared with theoretical predictions by W.T. Blackband.
Area coverage in mobile radio by quasisynchronous transmissions using doublesideband diminishedcarrier modulation
 Author(s): W. Gosling and V. Petrovic
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1469 –1476
 DOI: 10.1049/piee.1973.0303
 Type: Article
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Problems of area coverage are reviewed, and the means of reducing interaction between quasisynchronously operated doublesideband diminishedcarrier (d.s.b.d.c.) v.h.f. transmitters are considered. Carrier diminution and relative sideband phasing are shown to play an important role. Experimental results are given for a d.s.b.d.c.v.h.f. mobile radio system. The performance of a single transmitter is compared with that of three transmitters operated quasisynchronously. The superior coverage of the latter system is marked
Topological considerations in the design of optimum teleprocessing tree networks
 Author(s): I. Cahit and R. Cahit
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1477 –1481
 DOI: 10.1049/piee.1973.0304
 Type: Article
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A graphtheoretic approach to the design of optimum communication networks is given. The solution obtained satisfies the minimum cost weight, and is feasible and reliable. The paper also presents a new method of selecting the most reliable dataprocessing centre among the terminals. The efficient and simple generation of path matrices in a tree network is given. A design example is also presented.
Analysis of element admittances of a pair of staggered loop antennas
 Author(s): T. Bhattacharyya and K.K. Bandyopadhyay
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1482 –1484
 DOI: 10.1049/piee.1973.0305
 Type: Article
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The problem of a staggered array of two loops, parallel and driven, is considered, and its theoretical analysis is presented. Subsequently, investigations are made on the admittance of this array. The effect on admittance of varying the staggering distance is also studied. The measured results show a good agreement with the theoretical values.
Performance of multiphase coherent phaseshiftkeyed systems with intersymbol interference and Gaussian noise
 Author(s): T.S. Koubanitsas
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1485 –1488
 DOI: 10.1049/piee.1973.0306
 Type: Article
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A method is presented for the derivation of an upper bound to the probability of error in multiphase coherent phaseshiftkeyed (c.p.s.k.) systems with intersymbol interference and additive Gaussian noise. The method uses the unionbounding technique, in conjunction with a seriesexpansion method, and also simple bounds to the moments of the interference terms. The bound is general in application and fairly simple to compute. To illustrate its efficacy, the bound is computed for a specific case of practical interest, and is graphically compared with measures of the error performance derived by other methods. A plot is also presented that demonstrates the rate of convergence of the power series, representing the bound.
Effect of parameter variations on inductionmotor transients
 Author(s): I.R. Smith and B. Hamill
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1489 –1492
 DOI: 10.1049/piee.1973.0307
 Type: Article
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Previous work on the transient performance of induction motors has paid little attention to the effect of variations in winding parameters from some assumed stator/rotor allocation. This paper shows that, based on factorialdesign considerations, a response equation may be derived that expresses the severity of the transient current or torque, or the runup time, in terms of a nominal response, together with contributions derived from the parameter variations. The coefficients of the response expressions for the transients that follow several switching and reswitching operations of a 5.6 kW motor are given. The errors introduced by the use of a fractional factorialdesign plan are shown to be small, and mention is made of typical situations in which the technique described may be useful.
Universal equivalent circuit for steadystate operations of induction motors
 Author(s): W.S. Leung and C.T. Choy
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1493 –1498
 DOI: 10.1049/piee.1973.0308
 Type: Article
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A new universal equivalent circuit is developed based on the crossfield theory. By using the appropriate circuit parameters, the equivalent circuit can be used to analyse the steadystate performance of all induction motors whose rotors are symmetrical but whose stators may be symmetrical or otherwise. Applications of the equivalent circuit to a variety of commonly used induction motors are discussed. Simulations of a number of different connections are presented, and an example of the simulation is evaluated with a digital computer.
Normal force in singlesided linear induction motors
 Author(s): E.M. Freeman and D.A. Lowther
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1499 –1506
 DOI: 10.1049/piee.1973.0309
 Type: Article
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It is shown that the normal force in a singlesided linear induction motor can be appreciable, and that it is highly dependent on the speed and terminal conditions. Two simple theories are presented, and these are compared with experimental results. Tests were performed on both static and dynamic machines showing the variation of normal force with frequency and speed, and the effects of pole changing and plugging. It is concluded that the normal force and the possible changes that can occur in its magnitude and direction are highly significant design factors.
Fully slotless turbogenerators
 Author(s): E. Spooner
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1507 –1518
 DOI: 10.1049/piee.1973.0310
 Type: Article
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The constraints restricting the choice of rotor length and diameter in a turbogenerator are relaxed, and much higher airgap flux densities are possible if a fully slotless construction is employed. Capacities about three times greater than can be achieved with conventional machines are possible, and there is wide scope for optimising the dimensions and loadings of machines of present day ratings; e.g. a 660 MW slotless machine could show savings of about 2 MW in losses, 4 m in length and 150 t in mass and would have reactances more suited to stable operation. Gas or liquid cooling of the active parts could be employed without special problems.
Force on a moving conductor due to a magnetic pole array
 Author(s): D. Schieber
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1519 –1520
 DOI: 10.1049/piee.1973.0311
 Type: Article
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The braking force per pole pair exerted on a very long nonmagnetic metal sheet moving in the air gap of a magnetic pole array is investigated. An approach leading towards the design of the most efficient layout with a maximum force of interaction is described.
Further studies on wave propagation in overhead lines with earth return: impedance of stratified earth
 Author(s): M. Nakagawa ; A. Ametani ; K. Iwamoto
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1521 –1528
 DOI: 10.1049/piee.1973.0312
 Type: Article
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A more rigorous and general solution for the earthreturn impedance of overhead transmission lines than those given by Carson, Wise et al. is developed in the paper. In particular, the solution derived permits the earthreturn path to be considered as three layers of differing resistivities, permittivities and permeabilities. The solution agrees with those previously derived under the same given conditions. Calculated results are presented to show the effects of the various parameters of the formulation developed. A stratified earth causes marked differences in the earth impedances and the resultant wave deformations from the homogeneous case. The depth of a layer is a significant factor to the value of the stratifiedearth impedance. In comparison with the findings of earlier work, studies based on the formulation of the present paper indicate that, although displacement currents can influence earthreturn impedances, this is only likely at frequencies in excess of 1 MHz and under the conditions of high earth resistivity and low conductor height. The effect of a ferromagnetic earth layer is shown to be significant at low frequencies. The attentuation of travelling waves is much less than that for the ordinary earth.
Rectifier action with constant load voltage: infinitecapacitance condition
 Author(s): M. Hancock
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1529 –1530
 DOI: 10.1049/piee.1973.0313
 Type: Article
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The paper presents an analysis of a 3phase fullwave bridgerectifier system with constant load voltage, and with series resistance and inductance in the a.c. source. It is shown that four different operating modes or conducting patterns may occur, according to the phase angle of the source impedance and the magnitude of the load voltage. The results given include a complete set of output voltage/current characteristics from open circuit to short circuit, for the full range of possible source impedances, together with details of the source and bridge currents.
Current paths and potential distributions in mechanical connectors and busbar clamps
 Author(s): T. Farrell
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1531 –1532
 DOI: 10.1049/piee.1973.0314
 Type: Article
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The current flow and potential distribution in some simple connectors is analysed. A standardised location of potential probes when making contact resistance measurements is recommended, and resistances so obtained are free from erroneous implications to the connector's performance. A procedure offering a means of estimating the true contact resistance is outlined.
Digital simulation of the hysteresis motor
 Author(s): R.D. Jackson
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1533 –1537
 DOI: 10.1049/piee.1973.0315
 Type: Article
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Equations developed to study the behaviour of hysteresis motors require some representation of the ferromagnetic hysteresis nonlinearity. In this paper, a method of representing hysteresis, which includes the effect of minor loops, is described and included in a computer solution to find the motor airgap field. The work has been done using circumferentialflux motors, but the method can also be applied to radialflux motors. Terminal voltage/current characteristics from the computer model show the same overall behaviour as experimental results, and agreement is also found between the computed and experimental airgap fluxdensity waveforms. Possible improvements in the digital model are indicated.
Power factor of thyristorcontrolled singlephase resistive load
 Author(s): W. Shepherd and P.J. Gallagher
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1538 –1539
 DOI: 10.1049/piee.1973.0316
 Type: Article
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Validity of neglecting transfer conductances in transientstability studies
 Author(s): V.R. Sastry
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, page: 1539 –1539
 DOI: 10.1049/piee.1973.0317
 Type: Article
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Method for predicting the dynamic response of a variablereluctance stepping motor
 Author(s): P.J. Lawrenson ; A. Hughes ; I.E.D. Pickup ; D. Tipping
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1539 –1540
 DOI: 10.1049/piee.1973.0318
 Type: Article
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Description of linear multivariable process dynamics using continuous and discrete output equations
 Author(s): D.J. Sandoz
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1541 –1544
 DOI: 10.1049/piee.1973.0319
 Type: Article
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From the standard continuous form of the statespace and measurement equations, formulations of process dynamics defined in terms of inputs and outputs alone are developed. The derivation and solution of a continuousoutput equation leads to a discrete output equation that is based on multiple derivatives of process outputs. This discrete solution is further developed to establish an output equation that is defined in terms of process past inputs and outputs.
Structure of Kron's polyhedron model and the scattering problem
 Author(s): H. Nicholson
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1545 –1557
 DOI: 10.1049/piee.1973.0320
 Type: Article
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Kron proposed a polyhedron network model or ‘automaton’ to represent a wide range of physical system problems. The model includes a sequence of higherdimensional structures, each formulated by an orthogonal electrical network with closed and open paths. A set of electromagnetic waves is assumed to propagate across the polyhedron, and many other physical concepts are introduced intuitively into the model, including those concerned with multidimensional ‘generalised’ machines, thermodynamics, fluid flow and statistical phenomena. The present work highlights the significance of the orthogonal electrical network in the polyhedron structure, and it is shown that a similar structure exists in the general scattering representation of a flow process. The formulation of the scattering problem would then appear to provide an analytical basis for many of the physical concepts discussed by Kron. It is also shown to be associated with the system problems concerned with the multimachine power system, leastsquares estimation and linear optimal control and filtering. Kron's polyhedron model and the scattering problem thus incorporate similar basic features, which appear to be of fundamental importance in general system theory.
Stability of linear constant multivariable systems
 Author(s): P.A. Cook and E.A. Freeman
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1557 –1558
 DOI: 10.1049/piee.1973.0321
 Type: Article
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Electric strength of liquidfilled plastics tape insulation
 Author(s): R. Croxford
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1559 –1564
 DOI: 10.1049/piee.1973.0322
 Type: Article
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The paper describes electricalbreakdown experiments performed on thin, flat packs of plastics film impregnated with mixtures of dielectric liquids of different composition. Using this technique, it is possible to distinguish the direct effect of the ratio of the liquid and solid relative permittivities on the electric strength of the composite from the characteristics of particular materials. It is shown that the impulse electric strength of the composite depends only on the stress in the liquid at the breakdown site and its electric strength, but, for mineral oil or silicone oil alone, the composite may have a considerably greater electric strength than expected on this basis. The magnitude of the increase is governed by the solid.
Timedependent current leading to a spark
 Author(s): A.E.D. Heylen
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1565 –1567
 DOI: 10.1049/piee.1973.0323
 Type: Article
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The Schade and the Kachickas and Fischer theories for the timedependent current leading to a spark consider secondary ionisation by positive ions and photons, respectively; they are adapted here for photon and positiveion secondary ionisation at the cathode. The theories are then extended to include simultaneous secondary ionisation by positive ions and photons. It is shown that, for small overvoltages, the extended Schade theory is reduced to the more accurate Davidson theory. However, no such reduction appears possible for the Kachickas and Fischer theory. The advantage of the Schade theory is that it gives a better engineering insight into the development of the timedependent current leading to a spark than does the mathematical derivation by Davidson; also, no. subsidiary experiment is required to derive the currentgrowth constant.
Measurements of the currentzero behaviour of constantpressure axialflow electric arcs in nitrogen
 Author(s): D.R. Topham
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1568 –1574
 DOI: 10.1049/piee.1973.0324
 Type: Article
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It is shown that the equations for the arc in constantpressure axial flow can be described in terms of nondimensional variables that account for the effects of changes in the gasflow velocity, pressure, arc length and circuitelement values. Experiments in nitrogen confirm the predicted scaling laws for arcs with an impressed linear current wave, as well as arcs for which an added parallel capacitance causes a strong arccircuit interaction. Sinusoidal current waves up to 150 A peak were used at flow velocities up to 300 m/s and pressures up to 2.5 atm.
Calculating the surface fields of conductors in corona
 Author(s): M. Khalifa and M. AbdelSalam
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1574 –1575
 DOI: 10.1049/piee.1973.0325
 Type: Article
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Study of methods of computing transition matrices
 Author(s): A. Zinober and M. Healey
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 12, p. 1575 –1576
 DOI: 10.1049/piee.1973.0326
 Type: Article
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