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Electrical Engineers, Proceedings of the Institution of

Issue 9 • Date September 1970

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Displaying Results 1 - 25 of 28
  • Investigation of modulated corrugated aerial for frequency scanning

    Publication Year: 1970 , Page(s): 1729 - 1734
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (808 KB)  

    An investigation has been carried out on the characteristics of an array of periodically modulated corrugated trough elements for application as a phase-frequency scanning aerial. The theoretical analysis is based on the assumption that the corrugated surface is adequately approximated to by an equivalent surface reactance, and simple equations are presented for the propagation coefficient of the mode as functions of the structural dimensions and also of the frequency. The analysis takes into account the influence of the finite wall height of the trough, which is found to be an important parameter and must be chosen to maintain a constant value of attenuation coefficient over a limited frequency band. This is an extension of the work presented earlier by Oliner and Hessel. Experimental results are given for a 7-element array which adequately demonstrates the validity of the design equations, and therefore allows a practical aerial design to be carried out with ease. View full abstract»

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  • Analysis of two identical parallel arbitrarily located thin asymmetrical antennas

    Publication Year: 1970 , Page(s): 1735 - 1740
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (741 KB)  

    A method is presented for analysing two parallel arbitrarily located thin asymmetrical antennas. It is assumed that the system is point-symmetric, and current distributions along the dipoles are approximated to by polynomials with complex coefficients. Starting from the solution for this basic structure, three cases are analysed. The first is that of two identical, halfwave and fullwave parallel symmetrical dipoles in 45° echelon and when collinear, for which results according to the Chang-King 5-term theory are available. The simplest 2nd-order polynomial approximation of current results in self and mutual admittances which are in very good agreement with those of Chang and King, and only if very accurate current distribution is desired need the 3rd-order polynomial approximation be used. In addition, an asymmetrical dipole with a parasite and a sleeve dipole with a parasite are analysed starting from the basic structure and making use of superposition. View full abstract»

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  • Design of flared-horn primary feeds for parabolic reflector antennas

    Publication Year: 1970 , Page(s): 1741 - 1749
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1009 KB)  

    The paper describes the derivation of a simple design procedure by which the dimensions of a rectangular flared-horn primary feed, operating in the TE10 mode, may be determined for parabolic reflectors, having any f/d ratio and with either a rectangular or circular contour, so that maximum aperture efficiency is obtained. The design technique is based on achieving a best match between the principal component of the reflector focal-plane electric field and that electric field existing in the horn mouth during transmission. In addition, the design procedure predicts the value of the spillover power, the reradiated power, the relative edge-field illumination, the resultant reflector aperture-field distribution and the value of the maximum aperture efficiency obtainable for the given combination of horn feed and reflector. View full abstract»

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  • Some polynomial compositions of nonlinear feedback shift registers and their sequence-domain consequences

    Publication Year: 1970 , Page(s): 1750 - 1756
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (869 KB)  

    The polynomial representation of the cyclic nonlinear feedback shift register is investigated for its behaviour under the application of the dual and reverse operators. The concepts derived are extended to include composite polynomial structures. Invariances under either or both of the operators reveal some special types of feedback shift register (f.s.r.), and the sequence-domain consequences of these are explored. Palindromic, dual-symmetric, reverse-dual-symmetric, and skew-symmetric f.s.r.s are described, together with the conditions for existence, the numbers avaiable for a given register length and methods for their synthesis. View full abstract»

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  • Adaptive ambiguity resolution in automatic-radar design

    Publication Year: 1970 , Page(s): 1757 - 1766
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1424 KB)  

    The paper discusses the problem of ambiguity resolution in the range and velocity dimensions of an adaptive radar. In Part 1, the basic ambiguity problem is introduced, and the principles of ambiguity resolution are developed for the case of a radar which is ambiguous in one dimension only. In Part 2, the simultaneous resolution of ambiguities in range and velocity is considered. Part 3 discusses the impact of the ambiguity resolution requirement on adaptive radar design. The concept of `effective discrimination¿ is introduced, whereby the rate of removal of ambiguity must be moderated if track confusion is to be avoided, and the interdependence of measurements in the two dimensions is clarified. View full abstract»

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  • Signal filtering using hard-limited digital processing. Part 1: General description and performance with white-noise background

    Publication Year: 1970 , Page(s): 1767 - 1776
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1137 KB)  

    The effect of hard clipping on the filtering of a sampled narrowband sinusoidal signal embedded in wideband noise is assessed by simulating the processing system on a digital computer, with particular reference to a radar pulse-Doppler signal-processing system. The noise is assumed to be uncorrelated from pulse to pulse, and the signal processing is either completely coherent or is partially coherent and partially incoherent. The narrowband signal has either a constant r.m.s. amplitude or can fade slowly relative to the duration of a processing period. Tables of processing loss relative to an ideal system are given for different combinations of the digital-system parameters. View full abstract»

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  • Corrigendum: Attenuation characteristics of dominant mode in inhomogeneously filled transmission lines

    Publication Year: 1970
    Save to Project icon | PDF file iconPDF (71 KB)  
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  • Motorette tests: causes of variation in results

    Publication Year: 1970 , Page(s): 1777 - 1781
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (836 KB)  

    Four laboratories have tested motorettes specially prepared by a fifth, using a similar procedure to that recommended in AIEE 510 (IEEE 117). Heat aging was at 200°C and a 2.3: 1 difference in measured life was obtained between laboratories. Consideration of possible variations in procedure and testing have failed to establish any specific causes for the differences in the results, and it is concluded that the recommended procedure could not give an estimated maximum working temperature within better than 16 deg C. View full abstract»

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  • `Sum¿ and `difference¿ winding modulation with special reference to the design of 4/6-pole p.a.m. windings

    Publication Year: 1970 , Page(s): 1782 - 1792
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1525 KB)  

    In several respects, the design and performance of 4/6-pole p.a.m. windings present features which are contrary to the earlier and more usual forms of close-ratio pole-amplitude modulation (p.a.m.), and also to certain orthodox concepts relating to the harmonic m.m.f. content of the waveform of an induction motor. A very careful examination has therefore been given, in general terms, to the special features of 4/6-pole windings and to the effects both of subharmonics and of higher-order harmonics on the operation of an induction motor. (This latter part of the paper is of importance in relation to single-speed machines also.) Taking a 4/6-pole winding in 36 slots as an important example, the paper uses it to consolidate earlier p.a.m. windings with a number of later p.a.m. design methods. The differences between `sum¿ and `difference¿ modulation are also very fully considered. The whole paper serves to emphasise that pole-amplitude modulation is a general philosophy for polyphase windings, and not a specific design method. In principle, there is no limit to the number of design methods which may be evolved for embodying this philosophy in particular windings. View full abstract»

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  • D.C. dynamic braking of saturistor motor

    Publication Year: 1970 , Page(s): 1793 - 1798
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (673 KB)  

    The use of rotor-circuit saturistors during d.c. dynamic braking of a wound-rotor induction motor was found to result in faster braking. With an injected direct current electromagnetically equivalent to the rated stator current, the effect of saturistors was to reduce the stopping time from full-voltage no-load operation by 40%. Deceleration time for a saturistor motor can be predicted by the use of steady-state d.c. dynamic-braking torque, using an extension of induction motor theory. Saturistors designed for braking purposes were also found to improve motoring performance by giving higher stall torque and lower stall current. View full abstract»

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  • Stability of synchronous machines with 2-axis excitation systems

    Publication Year: 1970 , Page(s): 1799 - 1808
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1208 KB)  

    The paper describes analogue- and digital-computer studies of a synchronous machine with various 2-axis-excitation control systems. The steady-state and transient performances of the same machine are analysed, assuming different control schemes, such as rotor-angle control and asynchronised operation, and are compared with a conventional machine. The effects of damper windings, regulator time constants and stabilising circuits on the steady-state performance are shown by regulation curves. It is confirmed that the voltage-regulator loop gain has virtually no effect on steady-state stability, provided the winding with a.v.r. control is aligned with the flux axis by an angle regulator. The improved transient-stability limits obtained with high gains are shown. The fundamentally different transient behaviour of unregulated doubly excited and conventional synchronous machines is explained, and confirmed using accurate mathematical models of the machines. The method of `small oscillations¿ is applied to determine the speed stability of an asynchronised synchronous machine, and the transient performances of three different control schemes are compared in terms of swing curves and switching-time curves. View full abstract»

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  • Corrigendum: Transverse edge effects in linear induction motors

    Publication Year: 1970
    Save to Project icon | PDF file iconPDF (68 KB)  
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  • Choosing power-system voltage-regulator parameters by use of standard forms

    Publication Year: 1970 , Page(s): 1809 - 1814
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (650 KB)  

    The problem of adjusting the voltage-regulator gain, damping gain and time constant is considered. The `Whitley standard forms¿ are applied to a single-alternator system, and the voltage regulator is optimised with respect to the i.t.a.e. (integral of time × absolute value of error) criterion. It is shown, by experiments on a model system, that the optimisation yields good steady-state stability limits and, in consequence, underdamped system response. View full abstract»

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  • Dynamic-model studies of overhead equipment for electric railway traction. Sagged stitched- and compound-catenary equipment and further tests on sagged simple-catenary equipment

    Publication Year: 1970 , Page(s): 1815 - 1828
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1274 KB)  

    An account is given of the use of dynamically scaled models for predicting the behaviour of overhead equipment for railway electrification at 25 kV. The effects of varying the contact-wire sag and other dimensions of model compound- and stitched-catenary equipments have been measured. The maximum permissible speeds on equipment with the optimum sag were found to range from 200 to 224km/h (125 to 140 mile/h) when a single, undamped pantograph was used. Tests on model sagged simple-catenary equipment have also shown that a speed of 160km/h (100 mile/h) is still permissible even when large errors exist in the conductor tensions or when the droppers are to some degree incorrectly set. View full abstract»

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  • Starting methods for generator/motor units employed in pumped-storage stations

    Publication Year: 1970 , Page(s): 1829 - 1840
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1464 KB)  

    Arrangements which must be made for starting reversible pumped-storage plant in the pumping mode are reviewed, and the alternative starting methods are discussed. It is necessary to study the starting process in detail, together with the effect this has on the power system, because of the capacity of large pumped-storage plant, with the requirement that the machines be started during periods of low demand. The method chosen must be technically sound, reliable and economic. Two starting methods are considered in detail: asynchronous starting and synchronous starting. Disturbances imposed on the power system by the starting process are particularly important in asynchronous starting. The method discussed is related principally to the Korndorfer procedure. The effect on starting performance of varying the system constraints, together with the effect of other criteria, is examined. Theoretical predictions are compared in specific cases with test results obtained on conventional hydroelectric plant relating to both asynchronous and synchronous starting, to verify the representation employed. Typical theoretical results relating to 2 × 150MW and 4 × 300MW schemes are given. View full abstract»

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  • Passive low-power single-phase¿3-phase convertor

    Publication Year: 1970 , Page(s): 1841 - 1846
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (769 KB)  

    The paper describes a passive network for producing a balanced 3-phase output from a single-phase source. The novelty of the method centres on the observation that a single-phase supply can be regarded as a particular case of an unbalanced 3-phase system, and employs phase-balancing concepts which are derived from symmetrical component-measuring techniques. View full abstract»

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  • Discussion on ¿Application of test results to the calculation of short-circuit levels in large industrial systems with concentrated induction-motor loads¿

    Publication Year: 1970 , Page(s): 1846 - 1850
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  • Discussion on "Water-cooled generator connections"

    Publication Year: 1970 , Page(s): 1850 - 1852
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  • Discussion on ¿P.A.M. graded concentric windings for 2-speed single-phase induction motors¿

    Publication Year: 1970 , Page(s): 1853 - 1854
    Save to Project icon | PDF file iconPDF (338 KB)  
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  • Optimum Lyapunov functions and stability regions for multimachine power systems

    Publication Year: 1970
    Save to Project icon | PDF file iconPDF (191 KB)  
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  • Economic comparisons in planning for electricity supply

    Publication Year: 1970 , Page(s): 1855 - 1856
    Cited by:  Papers (1)
    Save to Project icon | PDF file iconPDF (326 KB)  
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  • High-order autocorelation functions of pseudorandom signals based on m sequences

    Publication Year: 1970 , Page(s): 1857 - 1863
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (769 KB)  

    The properties of the higher-order autocorrelation functions of pseudorandom signals based on m sequences are shown to depend on the existence of linear relationships between members of the m sequence and the way in which the m sequence is mapped into the pseudorandom sequence of real numbers. From the results presented, the autocorrelation functions of any order may be determined analytically for such signals. The particular properties of the autocorrelation functions of pseudorandom signals derived by symmetrical mapping from p-level m sequences are described, and the important case of the 4th-order autocorrelation functions of these signals is discussed in detail and illustrated by an example. View full abstract»

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  • Generalised Fourier methods for 1st-order distributed systems

    Publication Year: 1970 , Page(s): 1864 - 1868
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (514 KB)  

    Eigenfunction expansion of linear distributed systems is only possible when discrete solutions exist to the spatial-operator eigenvalue problem. 1st-order systems are naturally associated with a continuous spectrum, and a reduction to a finite lumped-system approximation is accordingly difficult. When the extended operator concept is used to introduce artificial periodicity, however, a discrete Fourier expansion becomes possible, yielding state-vector equations in the expansion coefficients. This generalised Fourier method particularly applies to distributed systems involving 1st-order spatial operators with 2-point boundary values. View full abstract»

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  • Theoretical analysis of harmonic instability in a.c.-d.c. convertors

    Publication Year: 1970 , Page(s): 1869 - 1878
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (996 KB)  

    There have been reports of difficulties encountered in the operation of high-voltage a.c.-d.c. conversion control schemes, particularly with reference to the so-called harmonic-instability phenomena. In the paper, an attempt is made to model the conventional convertor timing-loop control scheme using previously published concepts developed by the authors. This essentially enables the Z transformation to be used in assessing stability considerations. It is shown that this approach indicates likely troubles with conventional control schemes. A numerical example is given to show how the existence of a stability problem may be determined at the design stage, and a comparison of theoretical results and reported behaviour shows a good agreement. View full abstract»

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  • Allocation of poles and zeros

    Publication Year: 1970 , Page(s): 1879 - 1886
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (790 KB)  

    The theory of singular pencils of matrices is applied to the system matrix of a linear constant system. It is shown that the zeros of the McMillan form of the transfer-function matrix can be allocated subject to mild conditions. The poles of the McMillan form of the closed-loop transfer function can be allocated similarly. 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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