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Electrical Engineers, Proceedings of the Institution of

Issue 6 • Date June 1965

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Displaying Results 1 - 25 of 29
  • Aerial noise temperatures at 5650 Mc/s

    Publication Year: 1965 , Page(s): 1075 - 1080
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (545 KB)  

    The paper describes two sets of measurements of aerial noise temperature at a frequency of 5650 Mc/s in the allocated band for commercial radar, these being made with (a) an aerial pointing over the land and (b) an aerial pointing over the sea. The results are discussed in relation to theory and possible applications. View full abstract»

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  • Investigation of some high-speed switching properties of magnetic films

    Publication Year: 1965 , Page(s): 1081 - 1090
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1395 KB)  

    The use of thin, uniaxially anisotropic, magnetic films in binary-storage cells using the rotational switching system is described briefly. The apparatus used traces out automatically curves of cell output against switching current for switching pulses 6¿60ns long. Continuous films on conducting substrates were used and it was found that asymmetries appeared in the curves for the shorter pulses, owing to the field from eddy currents induced in the substrate opposing any changes in the cell setting. However, the curves became symmetrical if the film was in a multidomain state before the cell was set. The experiments also show that the reduction and distortion of the applied fields caused by intersecting conductors can be virtually eliminated by slotting the conductors but that segments ¿mm wide are permissible. Contrary to expectation, the drive current required to set the film cells increases with decreasing pulse length (e.g. 1A at 60ns, 2A at 15ns, 5A at 6ns); this effect is only partially explained by substrate eddy currents. The effects of the width of the drive and digit conductors on the required drive currents are explained by the propagation of magnetisation changes away from the edges of the conductor, probably caused by magnetostatic coupling within the film. Also, contrary to expectation, the digit-conductor width was found not to affect the digit current required for widths up to 5mm for films more than 800Å thick. Although this cannot be completely explained by the observed propagation of magnetisation changes, limiting the propagation by using an isolated patch of film produces the expected result that the digit current required to set the cell is proportional to the digit-conductor width. View full abstract»

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  • Investigation of the current gain of a composite transistor

    Publication Year: 1965 , Page(s): 1091 - 1098
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (782 KB)  

    An expression is derived for the complex current gain of a composite transistor. It is shown that the current gain of a composite transistor is influenced by the low-frequency current gain and cutoff frequency of the individual transistors. The emitter and collector depletion-layer capacitances and the extrinsic base resistances are also shown to influence the current gain of a composite transistor. It is found that there is a considerable difference between the current-gain characteristic of a composite transistor predicted by the equation for ¿ based on one-dimensional diffusion theory and that predicted by the first-order approximation. Measurements are made of the steady-state frequency response and the transient response of a composite transistor constructed from two alloy-junction transistors of the same polarity. Close agreement is found between the measured characteristic and the characteristic predicted by the equation for ¿ based on one-dimensional diffusion theory where the effects of extrinsic components have been taken into account. View full abstract»

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  • Subjective quality of television pictures impaired by random noise

    Publication Year: 1965 , Page(s): 1099 - 1102
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (510 KB)  

    Using a previously proposed quality-grading method, tests have been made of the effect of both flat and triangular random noise on still, monochrome, 625-line pictures typical of scenes in television broadcasting. 50% favourable opinions are obtained with a signal/weighted-noise ratio of 36db and 95% favourable opinions with a ratio of 39db. View full abstract»

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  • Direct computation of delay from attenuation

    Publication Year: 1965 , Page(s): 1103 - 1105
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (259 KB)  

    A rudimentary method of computation is developed by which an approximation to the group delay of minimum-phase networks can be obtained directly from the attenuation function without any reference to phase. The technique is especially suitable for use with a computer; it is illustrated by plots of the delays of the Butterworth filter and the Thomson network. Judged by these plots, the accuracy of the method is about 10%. View full abstract»

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  • Cambridge Electronics Section: Chairman's address. Seventy years of broadcasting

    Publication Year: 1965
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (116 KB)  

    First Page of the Article
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  • Resonant magnet network and power supply for the 4 GeV electron synchrotron Nina

    Publication Year: 1965 , Page(s): 1107 - 1126
    Cited by:  Papers (12)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1925 KB)  

    The paper describes the resonant magnet network and power supplies of the 4 GeV electron synchrotron Nina, now under construction at the Daresbury Nuclear Physics Laboratory, Cheshire. The requirements of high accuracy and uniformity in the magnetic guide field pose special problems in magnet-network arrangements, excitation methods and control, and these aspects of the accelerator design are discussed in some detail. Special emphasis is given to (a) the dynamic behaviour of the distributed resonant magnet network and its effects on the energy-storage-choke design, (b) the transient characteristics of the pulse power supply and (c) the part played by model and analogue-computer studies during the design stages. View full abstract»

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  • Simplified steady-state thermal calculations for naturally cooled transformers

    Publication Year: 1965 , Page(s): 1127 - 1134
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (783 KB)  

    Simplified cooling fluid-flow equations and temperature distributions are developed which are suitable for quick and easy application without recourse to a computer. These equations show how to determine the duct sizes for efficient cooling. The interaction between coil ducts and cooling tubes is examined, and a novel method of using cooling tubes is proposed and analysed. View full abstract»

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  • Three-speed single-winding single-phase induction motor

    Publication Year: 1965 , Page(s): 1135 - 1143
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (899 KB)  

    The pole-amplitude-modulation method of obtaining economic and efficient 2-speed and 3-speed operation of a normal 3-phase squirrel-cage induction motor with a single winding, developed by Rawcliffe and Fong, has been applied to the single-phase induction motor. The paper describes the theory and design methods, and presents experimental results obtained with a 3-speed 8/6/4-pole single-phase test motor. Performance of the motor at 6 poles and 4 poles is comparable with that of normal single-phase motors, while at 8 poles it is somewhat inferior. The winding is of a perfectly standard type. Ten terminals only are required for two speeds, and 12 terminals for three speeds, the control gear therefore being extremely simple. View full abstract»

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  • Forces on turbogenerator end windings

    Publication Year: 1965 , Page(s): 1144 - 1158
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1566 KB)  

    The complete distribution of the forces acting over the whole of a typical, 2-pole turbogenerator end winding of the involute type is studied and presented in a general form. Further, the way in which these results can be applied to calculate the forces for any other (2-pole) winding of involute type, without restriction as to size, is described. The basic results are presented in such a form that they can be used to determine the point-by-point distribution of forces for any condition of current loading. Additional results give the total forces experienced by individual coils of the winding. The method of calculation, which is based upon expressions for the force between any two short, straight, current-carrying conductors, is described. It is very simple and flexible and can be used to determine the distribution of force in any machine end winding or any other complex arrangement of conductors. The effects that changes in winding design have on the force distribution are studied. It is shown that the cone angle, the spacing between involutes and the number of stator coils (for fixed electrical loading) all have a considerable influence on the forces. In the cases of the involute spacing and the coil number, simple empirical equations describing their effects are developed. With regard to accuracy of representation, it is shown that the effects of air-gap magnetisation are unimportant; that errors due to the neglect of coil cross-section are of fixed sign and about 5?10% of the true force values; and that errors due to neglect of the machine end surface are generally ?10%. The influences of the stator casing and rotor shaft and retaining ring are briefly considered. The forces due to rotor winding currents are examined, and it is found that, whilst the peripheral and axial components are generally unimportant, the radial component can be as large as 50% of that due to stator currents, and is directed outwards. Brief consideration is given to certain eddy-current ef- fects, and, in conclusion, it is indicated that, owing to these effects, forces computed using values of the subtransient reactance, or indeed actual currents flowing at the instant of short-circuit, will be too high. View full abstract»

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  • Single-phase two-speed pole-change motors using phase-mixing techniques

    Publication Year: 1965 , Page(s): 1159 - 1172
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1373 KB)  

    The paper describes how the phase-mixing techniques which have previously been applied to 3phase operation may be extended for use in single-phase machines. A description is given of the operation of the previous 3phase versions when single-phase connected, and a subsequent analysis shows how windings which are harmonic-free at both speeds may be formed. The material is supported by some practical tests in which an example of the new two-speed windings is compared with a single-speed winding in a similar frame. View full abstract»

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  • Conductor vibration - theoretical and experimental investigations on a laboratory test span

    Publication Year: 1965 , Page(s): 1173 - 1179
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (949 KB)  

    The behaviour of a test span, artificially excited into transverse vibration, is studied. The decay mechanism is particularly analysed. It is shown that the decay is of the form of a step curve. The phenomenon is found to appear markedly in highly damped spans, but may be easily overlooked if the damping is small. Damping measurements in a laboratory test span by using the decay method are discussed. It is shown that the commonly used logarithmic decrement does not give significant information on the performance of a vibration damper. From the equations given in the paper, it is possible, from decay measurements, to calculate the power consumption which is recommended as a measure of damper efficiency. View full abstract»

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  • Sheffield Sub-Centre: Chairman's address. Protection of a distribution network

    Publication Year: 1965 , Page(s): 1179 - 1180
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (281 KB)  

    First Page of the Article
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  • North Staffordshire Sub-Centre: Chairman's address. F.H.P. motors and their place in the electrical industry: some interesting points of design and manufacture

    Publication Year: 1965 , Page(s): 1180 - 1181
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (291 KB)  

    First Page of the Article
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  • A.C. machine windings with reduced harmonic content

    Publication Year: 1965
    Cited by:  Papers (1)
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  • Proposed modification to a solid-rotor alternator

    Publication Year: 1965
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  • Instrument for measuring magnetostrictive strain of silicon-iron single crystals

    Publication Year: 1965 , Page(s): 1183 - 1186
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    An instrument is described which can measure strains of 10¿5 within ±5% over a distance of 2mm. The method is based on optical-lever amplification of the movement due to strain. A special multiple-beam interferometer is used for absolute determination of an internal secondary calibration. The latter is used during measurements of strain to make the instrument effectively a `null¿ device. View full abstract»

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  • A sampled-data nonlinear filter

    Publication Year: 1965 , Page(s): 1187 - 1196
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1128 KB)  

    The paper describes a method of constructing a general form of nonlinear filter in a digital computer. The filter is easily realised and optimised, and the technique provides for the gathering of the necessary statistical data. The memory part of the filter is based on a sampled-data Laguerre filter chain, which is particularly convenient in the expansion of nonlinear operators. The filter memory can be readily adjusted and auxiliary processing can be included for this purpose. An important relationship between product averages of linear filter outputs is described which is used to give economies in computation. The paper ends with the description of some results obtained in the solution of a nonlinear identification problem. View full abstract»

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  • Effect of a finite-word-length computer in a sampled-data feedback system

    Publication Year: 1965 , Page(s): 1197 - 1207
    Cited by:  Papers (44)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1065 KB)  

    When a digital computer acts as the compensating element of a sampled-data feedback system, the system performance is degenerated by the computational errors inherent in the finite-word-length machine. The statistical analysis presented in this paper enables the increase in the mean-square system error due to quantisation and computer roundoff errors to be assessed for a closed-loop linear sampled-data system. In fact, the loss in overall performance can be determined by slide-rule calculation for all computer word lengths. A further advantage of the present approach over previous work is that the necessary computations are performed on the conventional block diagram of the system, rather than its matrix equivalent. One application of the analysis is to specify the precision required in the digital compensator and peripheral equipment for consistency with the overall accuracy demanded of the closed-loop system. It also enables the selection of the programming technique which requires the shortest computer word length for this accuracy. As a means of verifying the analysis, the performance of two different digital compensators for a practical system are each compared with a counterpart having negligible quantisation and roundoff errors. View full abstract»

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  • Travelling-field theory of induction-type instruments and motors

    Publication Year: 1965 , Page(s): 1208 - 1214
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (735 KB)  

    For many years, controversy has raged about the best method of analysing the behaviour of induction-type instruments. On the one hand, the idea of a travelling field, appropriate to the induction motor, has been advanced for these instruments without much conviction. On the other hand, the technique of superimposing forces of interaction between one component of the magnetic field and the induced current of the other has been shown to offer a reasonable explanation. In view of the development of this type of instrument for radio measurements, consideration has been given in this paper to the basic conception of absorbing the momentum of a travelling field as a means of producing a mechanical force proportional to the power dissipated, and also to the application of this idea in examining the operation of induction-type instruments and motors. A simple theory which appears to be satisfactory over a wide range of frequencies emerges from this approach. View full abstract»

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  • Impulse breakdown of Perspex by treeing

    Publication Year: 1965 , Page(s): 1215 - 1220
    Cited by:  Papers (11)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (854 KB)  

    The spatial and temporal growth of discharge channels about a point electrode in Perspex has been investigated using impulse voltages. The channels develop substantially at random. Evidence is produced showing that they consist of hollow nonconducting tubes in which a discharge must be struck before extension can occur. The discharge within a channel acts as a conducting extension of the point electrode, and further development occurs by intrinsic breakdown of the material at the end of the channel. The process is believed to be caused by avalanche formation, and material is evaporated until the rise in pressure of the gas within the ignited channel causes the discharge to be extinguished. View full abstract»

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  • Sample-shape effects in electric-strength measurements on porcelain at power frequency

    Publication Year: 1965 , Page(s): 1221 - 1225
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (606 KB)  

    Various shapes of test sample have been recommended for determining the electric strength of ceramics. The form described by the British Standards Institution (BS 1598: 1949) for a proof test for electric strength would normally be chosen, but this type always fails by surface flashover rather than by puncture through the material. It was therefore decided to compare the electric-strength values obtained from five sample shapes (including a thinner version of the BS sample), all prepared from one batch of h.v. porcelain, produced by the same forming process and fired together. The thickness of the porcelain, the surface finish and the electrode material were varied, but other factors influencing the results were standardised. All samples were inspected for faults visually, by a fluorescent-penetrant method under ultraviolet light, and in some cases by X radiography. The fluorescent-penetrant method was very quick and easily applied, and more successful in detecting flaws than X ray inspection. On the bases of the electric-strength results, their consistencies of determined values, and the ease of manufacture and test procedure, an 80mm-diameter disc with a spherical depression in one face, using fired-on silver electrodes on a ground surface, was found to be most satisfactory. View full abstract»

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  • Ionisation and irradiation effects in high-voltage dielectric materials

    Publication Year: 1965 , Page(s): 1226 - 1236
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1410 KB)  

    A study of the chemical changes produced by exposure of dielectric materials to high-energy ionising radiation has shown that the effects are similar to those involved in electrical deterioration during stress aging and when ionisation has taken place in the dielectric. The principal effects observed in hydrocarbons and polymeric materials after exposure to radiation are: the crosslinking of the molecules to form an infusible gel structure; the evolution of hydrogen and low-molecular-weight fragments; molecular degradation by main-chain scission; the formation and annihilation of unsaturated groups; and, in the presence of air, processes of oxidative degradation. The corresponding electric stress and ionisation phenomena are: wax or `cheese¿ formation in solid-type cables; the gas evolving characteristics of paraffinic oils; the embrittlement of insulating paper; the formation of double bonds in aged cable oils, as evidenced by increased absorption in the ultraviolet region; and the oxidation effects with air resulting in an increase in power factor. While the mechanisms of radiation-induced change are not yet completely understood, they should throw light on the corresponding electrical stress and ionisation phenomena. Some of the methods used to protect organic systems against the effects of high-energy radiation are also satisfactory in reducing electrical effects, and a study of these protective mechanisms should be beneficial in the field of high-voltage dielectrics. View full abstract»

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  • Insulating properties of high vacuum

    Publication Year: 1965 , Page(s): 1237 - 1248
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1805 KB)  

    Recent experimental work on the insulating properties of high vacuum is systematically reviewed. A résumé of the prebreakdown conduction phenomena is given; in small gaps, the steady prebreakdown currents appear to be due to a modified type of field emission, while in longer gaps the contamination on the electrode surfaces gives rise to an ion-exchange mechanism, which is responsible for the microdischarges associated with these gaps. The parameters affecting the breakdown strength of a vacuum gap, and the different hypotheses postulated to explain the mechanism of breakdown, are considered in detail. No single hypothesis is able to account for all the experimental results reported, but it appears that a transition from one type of mechanism to another takes place as the interelectrode gap is increased. The paper also considers the important practical aspects of breakdown across solid insulating surfaces in vacuum. View full abstract»

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  • Report of the discussion on ionisation and irradiation effects at the Conference on Dielectric and Insulating Materials, 8th April 1964

    Publication Year: 1965 , Page(s): 1248 - 1250
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Aims & Scope

The Proceedings of the Institution of Electrical Engineers was published by the IET between 1963 and 1979.

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