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Electrical Engineers, Proceedings of the Institution of

Issue 1 • Date January 1965

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Displaying Results 1 - 25 of 34
  • Inaugural address. Science and engineering

    Publication Year: 1965 , Page(s): 1 - 8
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  • Chairman's address: Electronics Division. Through communications to electronics

    Publication Year: 1965
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  • Some applications of the scattering matrix

    Publication Year: 1965 , Page(s): 15 - 20
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    The scattering matrix is now sufficiently well known to become a useful tool in formalising the discussion of circuit behaviour in terms of wave concepts. Some examples are given to illustrate the utility of the scattering approach in describing the operation of such devices as circulators, hybrid junctions and negative-impedance, amplifiers. The treatment is aimed at the circuit engineer who is conversant with the matrix methods of circuit analysis yet unfamiliar with the application of scattering methods to the class of problem in which wave concepts are a real advantage. View full abstract»

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  • Some orbits for communication-satellite systems affording multiple access

    Publication Year: 1965 , Page(s): 21 - 30
    Cited by:  Papers (1)
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    The paper considers the influence of orbital parameters on the economic provision of simultaneous multiple interconnections between large numbers of earth stations in a global communication-satellite system. In order to provide direct communication between many countries which may be widely separated geographically, and also to avoid certain technical problems, it is most important to provide the interconnections wherever practicable on a one-hop basis. It is also desirable that each earth station shall work simultaneously to as few satellites as possible. These requirements can most readily be met by a system of geostationary satellites. However, such a system may prove unacceptable from other points of view (e.g. that of transmission delay). From an examination of the relations between coverage zones, orbital parameters and number of satellites required, it is concluded that large coverage zones may also be obtained with relatively few satellites by using systems in which each satellite follows the same earth track as its predecessor. The coverage provided by a number of such systems is discussed. View full abstract»

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  • Effects of polarisation on a medium-frequency sky-wave service, including the case of multihop paths

    Publication Year: 1965 , Page(s): 31 - 39
    Cited by:  Papers (1)
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    Ionospheric propagation at medium frequencies depends almost entirely on the ordinary wave, which is, in general, elliptically polarised. This paper describes coupling losses which occur when this wave is transmitted and received with vertical aerials, it also discusses additional losses caused by changes of polarisation when intermediate earth reflections occur. Formulas are given, permitting the various losses to be estimated; these are necessarily approximate, because they are based on the simple ray-theory approach. By way of example, curves are given showing the calculated losses for one typical frequency and angle of incidence. View full abstract»

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  • Magnetic-film logic. A theoretical and experimental study of a system using magnetic films and conducting loops

    Publication Year: 1965 , Page(s): 40 - 48
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    The general principles of a proposed logic system using magnetic films are described. Groups of binary storage cells are coupled by means of short planar conducting loops close to the film on a conducting substrate. A theoretical analysis is made of the current induced in the loop when a storage cell on it is read. Currents of 250mA, decaying to 50mA in the first 10ns, are expected. Experiments on the properties of a short loop coupling the cells are described, the measured currents being in general agreement with those predicted over the possible range of measurement, provided that the effects of the substrate in setting film cells are separated from the effects of the loops. It is concluded that, although a complete logic system could be made using the proposed technique, the rapid decay of the currents used to set the cells would require the use of very fast pulse generators, and the system could not complete economically with conventional transistor logic of the same speed. The experiments show the practical possibility of two forms of nondestructive-readout store. View full abstract»

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  • Method for measurement of plane resistors at microwave frequencies

    Publication Year: 1965 , Page(s): 49 - 54
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    The determination of the resistance of plane dissipative layers by impedance measurement is treated. Special attention is devoted to the range 1¿104¿ per square at 7Gc/s. Formulas are derived from transmission-line theory by making certain approximations, and the ranges of validity of these approximations are discussed. For 10¿300¿ per square, a simple graphical method is given. Experimental results show that the h.f. and d.c. resistances for two kinds of layers agree, but that a third kind shows substantial differences between the two resistances. In an Appendix a formulation of the input impedance of transmission lines is proposed that is specially suitable for transmission lines consisting of sections with different propagation coefficients. View full abstract»

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  • Chairman's address: Power Division. Development in power engineering

    Publication Year: 1965 , Page(s): 55 - 61
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  • Discussion on "Lightning flashovers on the British grid"

    Publication Year: 1965
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  • New method of presenting cooling data for aircraft electrical machines

    Publication Year: 1965 , Page(s): 63 - 70
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    In blast-cooled electrical machines in aircraft, the minimum permissible mass flow of cooling air, the electrical output, the air outlet pressure (a function of aircraft altitude), the air inlet temperature (a function of aircraft speed and altitude) and the pressure drop across the machine are all related to each other. Experimental data concerning these quantities are obtained from rating tests on a prototype machine, and are generally presented graphically by means of a `rating-data chart¿. This paper describes a new form of rating-data chart, consisting of four component graphs. It has been derived from the heat-transfer and pressure-drop correlation equations of the physical system, and it expresses mass flow as a function of electrical output, pressure and temperature, and pressure drop as a function of mass flow, pressure and temperature. This form of presentation enables it to cover accurately the wide ranges of pressure and temperature which obtain in modern high-performance aircraft. The accuracy of the new form of chart has been assessed from charts for five machines, and is considerably greater than that of the simpler form of chart generally used at the present time. View full abstract»

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  • Electrical automatic controls for space heating

    Publication Year: 1965 , Page(s): 71 - 83
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    Postwar developments in building have increased the importance of automatic controls for heating and air-conditioning installations because of the demand for comfortable environmental conditions and the large potential saving of fuel obtainable with appropriate controls. The reasons why the actual performance of heating controls is often unsatisfactory are considered. The characteristics of buildings and heating systems affecting the design and selection of automatic controls are discussed, and the principal elements of control systems are described, particular attention being devoted to improvements considered necessary to overcome difficulties in application. The application of these elements to typical systems of electrical heating, conventional central heating and air conditioning is then considered, and the paper concludes by discussing the problems of installation and maintenance and demonstrates how these can be alleviated by suitable design procedures. View full abstract»

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  • Discussion on ¿Conductor oscillation on the 275 kV crossing over the Severn and Wye¿

    Publication Year: 1965 , Page(s): 84 - 86
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  • Discussion on current ratings of plastic-insulated cables

    Publication Year: 1965 , Page(s): 86 - 88
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  • Gas-pressurised lapped-polythene dielectric for extra-high-voltage power-cable systems

    Publication Year: 1965
    Cited by:  Papers (2)
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    The paper describes an experimental investigation of the electrical, physical and mechanical properties of lapped-polythene dielectric. From the levels of impulse-breakdown stress and discharge-inception stress obtained, the use of this dielectric appears to be a promising method of operating low-permittivity low-loss insulation at stresses comparable with those currently employed in paper-insulated power cables at the highest transmission voltages. After consideration of other design aspects, a specification for 275 kV cable is given, based upon the experimental results obtained. The problem of providing terminations is also considered, and work leading to the design and testing of 275 kV capacitance-graded sealing ends is described. View full abstract»

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  • Impulse-strength measurements on compressed-gas insulation for extra-high-voltage power cables

    Publication Year: 1965 , Page(s): 103 - 108
    Cited by:  Papers (13)
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    Impulse-flashover measurements on a number of solid insulating materials in compressed-gas atmospheres at pressures up to 500 lbf/in2 are described. From the results of tests made with uniform-field and concentric-cylinder electrode systems, it is concluded that flashover occurs when the breakdown stress of the gas itself is reached at any point. The influence upon gas breakdown of placing thin coverings of solid insulating material in contact with metallic electrodes has also received attention. With a variety of coverings, improvements in impulse strength of approximately 50% were obtained with nitrogen and to a lesser, although still significant, extent with sulphur hexafluoride. The general levels of breakdown stress obtained are considered in relation to possible designs of extra-high-voltage power cables employing compressed gas as the major insulation. View full abstract»

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  • Some economic aspects of extra-high-voltage underground cables

    Publication Year: 1965 , Page(s): 109 - 118
    Cited by:  Papers (1)
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    Some of the factors affecting the cost of cable circuits in the main transmission network are discussed. The conclusions are reached that (a) voltage-dependent losses can assume an economic significance one order of magnitude greater than current-dependent losses, (b) optimum conditions have already been reached at a system voltage of 275 kV for existing cable designs and (c) technically improved designs are desirable at higher system voltages. An attempt is made to estimate the capital cost, total annual charge and current-carrying capacity of cable designs for 275 kV and 400 kV systems employing dielectric materials other than oil-impregnated paper. The conclusion is reached that considerable technical advantages and significant economic advantages should be achieved if designs employing either a gas-filled polyethylene-tape dielectric or a compressed gas as the cable insulation could be successfully developed. View full abstract»

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  • Discussion on ¿High-voltage power-transformer insulation¿

    Publication Year: 1965 , Page(s): 119 - 123
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  • Discussion on "Magnet power supply for Nimrod"

    Publication Year: 1965
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  • Discussion on "Layer-type transformer-winding cooling factors derived from analogue solution of the governing equations"

    Publication Year: 1965 , Page(s): 125 - 126
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  • Proposed modification to a solid-rotor alternator

    Publication Year: 1965
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  • Chairman's address: Science and General Division. The design and control revolution

    Publication Year: 1965 , Page(s): 127 - 136
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  • Extremum or hill-climbing regulation: a statistical theory involving lags, disturbances and noise

    Publication Year: 1965 , Page(s): 137 - 150
    Cited by:  Papers (3)
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    Extremum or `hill-climbing¿ regulation is the technique of optimising the performance of a continuous process by trial-and-error adjustment of the controlled variables. A highly simplified model of a process is considered here. It contains a convex quadratic characteristic or `hill¿, which represents the graph of the controlled variable versus the performance. This is disturbed both vertically and horizontally by Brownian motions, and the process also involves dynamic lags and measurement noise. Under certain conditions which are discussed, the problem of designing the best regulator is related to a nonstationary filtering problem, in which the time-varying parameters are periodic or random, according to the nature of the searching strategy. This related problem has been examined by analogue computation and theoretical analysis in various asymptotic conditions. The results are interpreted to show how the best possible extremum regulator is constructed. View full abstract»

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  • Compensation of a.c. control systems subjected to carrier-frequency fluctuations

    Publication Year: 1965 , Page(s): 151 - 158
    Cited by:  Papers (1)
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    A simple tracking filter is described that enables a parallel-T notch filter to be used for stabilising a.c.-control systems in which the frequency of the supply is subject to large variations. It is shown that the null parallel-T network, with the notch sharpened by feedback, has an effect in an a.c.-control system very similar to the effect of a phase-advance network in a d.c.-control system. This analysis simplifies the design of a.c.-compensating networks. Experimental work is included. View full abstract»

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  • Design and performance of thickness-shear vibrating quartz filter crystals

    Publication Year: 1965 , Page(s): 159 - 168
    Cited by:  Papers (1)
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    A study has been made of the effect of crystal-blank and electrode geometries on the performance of AT-cut and BT-cut quartz-crystal units intended for use in filters. Methods for controlling the frequencies and activities of unwanted modes of vibration are described, and it is shown that, by scaling the geometries, it is possible to translate crystal designs from one frequency to another. At frequencies below about 10 Mc/s, the unwanted spectrum of inharmonic thickness-shear resonances can be modified by the application of acoustically lossy material and the vacuum deposition of metal layers on to regions of the crystal which are most active for these modes of vibration. Above 10 Mc/s, it is found that the motional area of the crystal does not extend far outside the central electroded area, and, in view of this, it is possible to have more than one resonant section on the miniaturisation. Frequency/temperature between thickness-shear vibrations and influenced by the electrode thickness and same quartz blank, thereby obtaining a considerable degree of and activity/temperature characteristics, illustrating coupling high overtones of low-frequency resonances, are shown to be the method of mounting the crystal. View full abstract»

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  • Measurement of iron losses in magnetic sheet steel subjected to a high alternating magnetic field

    Publication Year: 1965 , Page(s): 169 - 178
    Cited by:  Papers (3)
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    Two sets of apparatus, one at Manchester the other at Sheffield, designed to measure iron losses in sheet-steel samples magnetised at high flux densities, are described. The measurements were carried out in each case by a different thermal method. Many of the difficulties common to all thermal measurements were present, and errors were only reduced by careful techniques and attention to detail. Two different methods, one electronic and the other dynamo-electric, of producing a sine wave of flux density at the required very high values were also developed and are described. Measurements have been made of the loss in several grades of silicon iron, with sinusoidal flux waveshapes up to flux densities of 22.5-24 kGs, according to the type of steel. The two different experimental systems have yielded answers in good agreement. Experiments are described which show that, for the materials tested, the loss directly proportional to frequency (hysteresis) reaches a saturation value at high flux density. Measurements of anomaly factor have been made, and some indication is also given of the way in which the total loss varies with form factor. View full abstract»

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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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