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Electrical Engineers, Proceedings of the Institution of

Issue 11 • Date November 1972

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Displaying Results 1 - 25 of 30
  • Circuit model for TRAPATT-oscillator cavities

    Publication Year: 1972 , Page(s): 1529 - 1537
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (888 KB)  

    The paper presents an analysis of the class of TRAPATT-oscillator circuit in which the avalanche diode is mounted at the end of a transmission line at a distance of approximately one halfwavelength (at the fundamental frequency of the oscillation) from a filter. This paper is concerned with the transformation of the current and voltage waveforms at the input to the cavity filter into the waveforms at the diode. It is shown from the transformation how the diode voltage consists of an extraction waveform and a trigger waveform. Expressions are derived which express the parameters of the trigger waveform in terms of circuit parameters. Consideration of the extraction waveform leads to the construction of a mode chart, which determines the bias current and voltage limits of the mode of operation. An analysis is developed which examines the properties of the mode chart and which is used to examine a cavity containing a filter with an exponential response. View full abstract»

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  • Erratum: Synthesis of threshold-logic networks using Karnaugh-mapping techniques

    Publication Year: 1972
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  • Statistical aspects of signal distortion in trunk-waveguide communication

    Publication Year: 1972 , Page(s): 1538 - 1548
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1509 KB)  

    The purpose of the paper is to develop a complete theory of signal distortion arising in waveguides due to modeconversion effects as caused by random waveguide irregularities. The general problem is approached by introducing the concept of a `travelling system function¿, which is a wave function travelling along the waveguide system in response to a unit impulse induced in the principal mode. In this way, the statistical variation of waveguide geometry is related to the statistical expectation of the system function. The results obtained are then applied, by way of illustration, to the solution of two particular problems: the expected waveguide attenuation, and the expected pulse distortion accompanying transmission of digital signals. The stability of statistical estimates obtained from measurements on experimental lengths of waveguide is examined. It is shown that, to reach reliable results, with close confidence limits, it is necessary to have substantial lengths of experimental waveguide available for tests. View full abstract»

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  • Perturbation techniques for semiconductor-device computer experiments

    Publication Year: 1972 , Page(s): 1549 - 1554
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    The range of problems which can be subjected to computer-simulation studies is increasing rapidly with the development of larger and faster computers. One can obtain results with adequate accuracy for most engineering purposes in simulating complex nonlinear problems such as semiconductor-device behaviour. The truncation error, inherent in any numerical technique, does, however, inhibit the use of such simulation techniques when the issue to be resolved is essentially in the nature of a small perturbation. A numerical perturbation technique which overcomes this problem is described. The method is illustrated by using it to evaluate the temperature sensitivity of voltage-reference diodes. The results are discussed, and suggestions are made concerning the range of problems to which the method can be extended. View full abstract»

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  • Synthesis of optimal receiver structure for signals phase modulated simultaneously by two binary processes

    Publication Year: 1972 , Page(s): 1555 - 1558
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (425 KB)  

    A generalisation of a previously described procedure for synthetising optimal receiver structures is developed and applied to a receiver for signals phase modulated simultaneously by a binary pseudonoise signal and a binary data signal. Both binary signals are represented by discrete Markov processes, and the phase and delay of the signals are represented by continuous Markov processes. View full abstract»

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  • z-transform analysis of nonuniformly sampled digital filters

    Publication Year: 1972 , Page(s): 1559 - 1567
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (807 KB)  

    The paper presents a z transform analysis of digital filters operated with nonuniform sample periods. The analysis is applicable to filters using a mean-square definition of transfer function, e. g. moving-target-indicator filters, and also to conventional digital filters. The evaluation of the frequency response of such filters using the analytic results of the paper leads to considerable savings in computation time over direct simulation methods. Nonuniform sampling of conventional digital filters is shown to result in a reduction of the effective Nyquist frequency, although, within this limited frequency range, additional control of the frequency response is possible for certain filters. A pole-zero diagram may be drawn for a nonuniformly sampled filter, and allows comparisons to be made with the corresponding uniformly sampled case. View full abstract»

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  • Polarisation-source formulation of electromagnetism and dielectric-loaded waveguides

    Publication Year: 1972 , Page(s): 1568 - 1574
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1038 KB)  

    A general formulation is presented for the diffraction of arbitrary fields by bodies exhibiting arbitrary variations of permittivity, permeability and conductivity. Piecewise-continuous and perfectly conducting bodies are included. The general solution to any diffraction problem is given as a single integral equation. Special attention is paid to time-harmonic fields and piecewise-constant bodies. This is illustrated by the computation of the cutoff characteristics of hollow, conducting waveguides of arbitrary cross-section loaded with dielectric tubes. Numerical results are presented for a square waveguide loaded with a solid dielectric rod. Experimental results are also reported. View full abstract»

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  • Maximally flat lowpass digital filters with sharp-cutoff characteristics

    Publication Year: 1972 , Page(s): 1575 - 1576
    Save to Project icon | PDF file iconPDF (227 KB)  
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  • Novel 4-quadrant thyristor controller

    Publication Year: 1972 , Page(s): 1577 - 1581
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    Various forms of a.c./d.c. 4-quadrant thyristor controllers, based on the circulating-current principle, are described. The relative advantages and disadvantages of circulating-current schemes and logic-interlocked schemes are discussed and a new current or voltage controller with a linear transfer characteristic is described. It is shown how such a scheme can be operated on the circulating-current principle with the circulating current effectively zero. View full abstract»

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  • New static controller for d.c. machines

    Publication Year: 1972 , Page(s): 1582 - 1586
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    The paper first considers the merits of a single-phase static Ward-Leonard drive. It is found that the drive has limitations which lead to poor speed regulation. A new, simple, static control device is described which gives improved performance. The control device can be used with an ordinary d.c. shunt machine to give shunt, series and compound characteristics in both generating and motoring modes. The device operates on the principle of monitoring the armature current, and, by the aid of feedback control, the field current is regulated to any desired machine operational mode. A theoretical analysis is verified by practical results. View full abstract»

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  • Operation and analysis of an invertor-fed-linear-motor system

    Publication Year: 1972 , Page(s): 1587 - 1594
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (917 KB)  

    The paper describes a 3-phase system in which a variable-frequency invertor is used to provide speed control of a linear induction motor. The steady-state operation and analysis are considered for invertor operation with two of the six main thyristors triggered simultaneously. The invertor and motor are analysed together, and theoretical results are shown to compare satisfactorily with those obtained experimentally. The comparison encompasses not only r.m.s. values, but also current and voltage waveforms. Results are presented for a published invertor circuit, and for a modified form of this circuit. View full abstract»

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  • Generalised-phase-comparator techniques for distance protection. Theory and operation of multi-input devices

    Publication Year: 1972 , Page(s): 1595 - 1603
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1120 KB)  

    A previous paper described the operation of phase-angle comparators in which discrete periods of the relaying signals are compared by means of pulse-generating circuits to obtain improved distance-protection performance. The present paper summarises the theory given in the earlier paper, but is principally concerned with the theory and operation of generalised multi-input devices. It is shown that such comparators effectively perform a simultaneous comparison of the relaying signals over different limits of comparison between each signal pair, and that this feature is desirable for the production of improved shapes of polar characteristic. A method whereby relay designers may derive comparator settings peculiar to differing characteristics is given, together with a realisability criterion, which determines whether a particular requirement may be met. The method of block-average modification, and its effect upon the time response of a typical comparator model, are explained. The paper concludes by taking a design example of the use of the new techniques for the production of a quadrilateral-type characteristic with improved discriminative performance. View full abstract»

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  • Simulation of power-system fault currents and voltages for protective-equipment testing

    Publication Year: 1972 , Page(s): 1604 - 1610
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1000 KB)  

    Artificial transmission lines have been successfully used in the past for protective-gear testing. However, the great increase in the power-system fault levels and transmission voltages experimented with in recent years has made it impractical and uneconomical to simulate correctly the high fault currents and time constants now encountered by means of artificial transmission lines. The paper describes two circuits to produce synthetically the fault currents and voltages required for protective-relay testing. Results obtained from small-scale models of the test circuits are illustrated and discussed. View full abstract»

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  • Recovery of mercury-arc h.v. d.c. interconnectors from backfire faults

    Publication Year: 1972 , Page(s): 1611 - 1615
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (471 KB)  

    A general classification of backfire faults is made according to the initial operating mode when blocking is attempted. With the help of a dynamic-simulation program, the behaviour of the faulty bridge and d.c. link are analysed under the different types of backfire. The blocking controllability of the bridge is thus investigated, in each case, with present-blocking control and with sequential-blocking control. The influence of the a.c.-system impedance on the reduction of backfire currents is also investigated. View full abstract»

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  • Power-series method of calculating eddy currents in nonmagnetic conductors

    Publication Year: 1972 , Page(s): 1616 - 1620
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (641 KB)  

    The use of the power-series method in problems involving eddy currents induced in nonmagnetic conductors is investigated. It is found that the application of the method must usually be restricted to resistance-limited currents, and the reasons for this are discussed. View full abstract»

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  • Simplified approach for estimating current unbalances in e.h.v. loop circuits

    Publication Year: 1972 , Page(s): 1621 - 1627
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (661 KB)  

    Electromagnetic and electrostatic unbalances due to the omission of transposition of transmission lines have been treated rather thoroughly, even though separately, in the literature. As e.h.v. lines become longer, and operating voltages are increased, it becomes evident that the line-charging currents are growing to the same order of magnitude as normal load currents. Consequently, it is often necessary to consider the effect of both line-charging and load currents in causing negative- and zero-sequence components of line current. When the total line is composed of sections with different cross-sectional configurations, the rigorous analysis becomes quite formidable. Therefore, a simplified equivalent circuit for an untransposed transmission-line section is proposed which relates more directly to familiar methods of circuit analysis. An important aspect of this method is that it brings out clearly the nature of the unbalance problem and thereby facilitates extrapolation, via good engineering judgement, to more complex networks. View full abstract»

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  • Opening address

    Publication Year: 1972
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    First Page of the Article
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  • Signalling systems in relation to 50 Hz electric traction

    Publication Year: 1972 , Page(s): 1628 - 1629
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (369 KB)  

    First Page of the Article
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  • Discussion at Colloquium on A.C. Traction after a Decade

    Publication Year: 1972 , Page(s): 1629 - 1640
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  • Erratum: Telecommunication systems in relation to 50 Hz a.c. electric traction

    Publication Year: 1972
    Cited by:  Papers (2)
    Save to Project icon | PDF file iconPDF (221 KB)  
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  • General principle for brushless synchronous machines and its application in an invertor-fed drive

    Publication Year: 1972 , Page(s): 1641 - 1642
    Cited by:  Papers (11)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (285 KB)  

    Rotor excitation of brushless synchronous machines may be obtained by a process of induction and rectification. Various embodiments of this principle are discussed briefly, and the paper then concentrates on one particular form in which the harmonic voltages of a thyristor-invertor output are harnessed to produce d.c. excitation of a 3-phase wound rotor. Test results are given for an experimental drive that yielded very good synchronous performance. A theoretical analysis of the system has been developed, and computed results agree closely with the tested characteristics. View full abstract»

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  • Summation of harmonics with random phase angles

    Publication Year: 1972 , Page(s): 1643 - 1648
    Cited by:  Papers (22)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (734 KB)  

    The magnitude of the sum of a number of harmonics, of the same order but with random phase angle, is derived, subject to certain assumptions regarding the phase distribution. Computation of the net magnitude is carried out for different types of individual harmonic amplitudes. When the number of individual harmonics is greater than about ten, it is shown that simplified expressions for the sum may be used. These lead to a simple approach, based on r.m.s. values, to the problem of determining an assessed level of harmonic content which would have a specific probability of being exceeded. Consideration is also given to the situation when just one or two harmonics are dominant, and a consequent simplification of an assessed level. The main results apply for instantaneous values of the net magnitude, but some subsidiary results given an indication of the likely behaviour over a continuous period of time. View full abstract»

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  • Ground-fault-arc suppression on series-and shunt-compensated lines

    Publication Year: 1972 , Page(s): 1650 - 1651
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  • Calculation of system-fault currents due to induction motors

    Publication Year: 1972
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  • Asynchronous or induction generator

    Publication Year: 1972
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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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