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Electrical Engineers, Proceedings of the Institution of

Issue 7 • Date July 1972

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Displaying Results 1 - 25 of 32
  • Nonarithmetical cellular arrays. Investigation of arrays for control functions

    Publication Year: 1972 , Page(s): 785 - 789
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (566 KB)  

    Nearly all the papers on cellular logic published recently have dealt with arithmetical functions. This paper proposes other areas where cellular logic may be usefully employed. These include switching arrays for computer highway control, arrays for signal routing in digital data networks and coding systems (e.g. where banks are online to a computer). Some examples of arrays for these applications are given. View full abstract»

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  • Erratum: Low-resistance thermometry

    Publication Year: 1972
    Save to Project icon | PDF file iconPDF (60 KB)  
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  • Model ionosphere for D region at summer noon during sunspot maximum

    Publication Year: 1972 , Page(s): 790 - 796
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (800 KB)  

    A model ionosphere, comprising electron-density and collision-frequency distributions for the midlatitude D region at summer noon during sunspot-maximum conditions, has been produced which will give satisfactory results for propagation at low and very low frequencies. The electron-density distribution above 68 km was based on a distribution, measured in a rocket, which was altered until fullwave calculations using it gave propagation parameters in agreement with the average observed values. Below 68 km, a C layer was found necessary to give the best fit to measured ground-interference patterns at 16 kHz. A comparison is also shown between a measured pattern of this kind and one calculated from the rocket distribution, which was obtained on the same day. View full abstract»

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  • Wave propagation and dispersion in space-time periodic media

    Publication Year: 1972 , Page(s): 797 - 806
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1410 KB)  

    The dispersion characteristics of electromagnetic fields are examined for waves propagating in a medium with a permittivity which is modulated periodically with respect to time and one spatial co-ordinate. By taking a guided-wave approach, which expresses the fields of arbitrary sources in terms of a superposition of modal solutions, it is shown that many properties of the individual modes may be inferred by means of wavenumber diagrams. These diagrams are easily constructed for the special case of a vanishingly small periodic modulation. By using coupled-mode consideration, this special case is extended to serve as a good approximation for finite modulation amplitudes. In addition to yielding information on the dispersion character of modal fields, it is shown that the wavenumber diagrams may be employed to extract the modal constituents of a plane wave scattered by a layer containing a space-time periodic medium. The principal far-field components of waves excited by a localised arbitrary source embedded in such a medium may also easily be obtained from the wavenumber diagrams. The guided-wave approach, together with its associated wavenumber diagrams, is thus shown to serve as a powerful tool in analysing and understanding a large class of phenomena, which includes the diffraction of light by sound and parametric effects in nonlinear media, as well as other aspects of wave interactions in material bodies. View full abstract»

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  • High-speed electro-optic diffraction modulator for baseband operation

    Publication Year: 1972 , Page(s): 807 - 814
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1056 KB)  

    A new kind of laser-beam modulator is described. An interdigital electrode structure deposited on an electro-optic crystal is used to produce a spatially periodic electric field which diffracts the laser beam within the crystal. Baseband operation is possible, and optical-pulse risetimes of 1.5 ns have been observed. The required drive power is only 7.5 nJ per pulse at 25 V, but this could be improved by scaling. The measured extinction ratio is 25 dB and this varies by less than ±1dB for a 10 K temperature change. The form of the modulator lends itself to inclusion in thin-film optical circuits. View full abstract»

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  • Capacitances of the shielded-pair line

    Publication Year: 1972 , Page(s): 815 - 820
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (491 KB)  

    Upper and lower bounds for the even- and odd-mode capacitances for the shielded-pair line are obtained in closed form using variational techniques that are applicable to inner conductors of arbitrary size and spacing. Results of computed normalised capacitances are catalogued in graphical form, together with an estimate of the error. View full abstract»

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  • Propagation coefficient of the Beverage aerial

    Publication Year: 1972 , Page(s): 821 - 826
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (746 KB)  

    The propagation coefficient for the current flowing in a Beverage aerial driven by a generator is derived from the compensation theorem. Comparison is made with measurements and with other theoretical methods. It is concluded that the attenuation increases approximately as the square root of the frequency, reaching a limiting value at high frequencies. The velocity of propagation is less than the free-space velocity, but tends towards it at high frequencies. Expressions for the characteristic impedance of the aerial are also given. View full abstract»

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  • Synthesis of linear-aperture distributions by pattern sampling

    Publication Year: 1972 , Page(s): 827 - 831
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (498 KB)  

    The classical Woodward method for synthetising linear-aperture distributions by pattern sampling is shown here to give a hybrid form of edge behaviour, in which the aperture distribution for the even part terminates in a pedestal (edge exponent ¿ = 0), while that for the odd part approaches zero linearly (¿ = 1). Hence the Woodward sampling functions are not the proper functions to use for representing an arbitrary aperture-limited function of either the order ¿ = 0 or ¿ = 1. Instead, a new set of sampling functions is constructed, for each order ¿ = 0 and 1 separately, that is capable of representing exactly an arbitrary pattern space factor of that particular order. View full abstract»

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  • Limitations of error-detection coding at high error rates

    Publication Year: 1972
    Save to Project icon | PDF file iconPDF (120 KB)  
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  • Generalised-phase-comparator techniques for distance protection. Basis of their operation and design

    Publication Year: 1972 , Page(s): 833 - 841
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1221 KB)  

    The basic theory and principle of operation of a new method of phase comparison for use in distance protection schemes is outlined. It is shown that the angular limits of comparison between signal pairs are determined by the setting of time-delay circuits, and that the new device is extremely variable. Comparator circuitry based on transistor logic is described in detail, and the effect of setting errors is analysed. The output from the device progresses from a short-duration pulse at the threshold to one of fixed duration, and the implications of such a response with regard to the overall performance are established. An introduction to generalised multi-input comparators is given, which, unlike conventional multisignal techniques, can be adjusted to give dissimilar limits of comparison between each signal pair. View full abstract»

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  • Control by digital computer of multiterminal h.v.d.c. system under fault conditions

    Publication Year: 1972 , Page(s): 842 - 850
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1225 KB)  

    A control philosophy is developed for a central digital computer to work online and to control the operation of a multiterminal h.v. d.c. system. It is assumed that each terminal of this system is equipped with fast analogue controllers of the conventional type which can accept commands from the central computer. The behaviour of a representative d.c. system has been tested on a laboratory model controlled under fault conditions by a PDP8 computer. It is shown that a satisfactory system-fault performance can be achieved with the philosophy and programming methods adopted. View full abstract»

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  • Computer method for design of electricity-supply networks

    Publication Year: 1972 , Page(s): 851 - 856
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (755 KB)  

    The paper describes an interactive computer method for designing electricity-supply networks, which provides the engineer with a choice of outline designs near the optimum. The interactive mode is used, not only to harness directly the calculating power of the computer, but also specifically to enable the computer to participate in the design process as a simulated designer. An initial design is suggested, and a sequence of designs is evolved by a series of amendments, the control action coming from either the computer or the engineer. A sample of the total number of constraints for each design is checked to obtain a statistical estimate of the security of the complete network. The information from each sample is processed to give a formalised representation of those features which indicate the strengths and weaknesses of a design, which can then be treated by a special algorithm to determine the appropriate modifications. The method is illustrated by an example involving 17 substations. Experience of the method indicates that solutions for networks of realistic size can be obtained in economical computing time. View full abstract»

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  • Generalised method of harmonic reduction in a.c.-d.c. convertors by harmonic current injection

    Publication Year: 1972 , Page(s): 857 - 864
    Cited by:  Papers (70)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (847 KB)  

    The paper describes a general theory for a new method of current harmonic reduction in a.c.-d.c. convertors. The principle of the method is to modify the current waveforms on the d.c. windings of the convertor transformer by injecting harmonic currents at a particular frequency. Experimental results carried out prove that the new method is effective in reducing the alternating-current harmonics, and that it is applicable to any type of convertor. View full abstract»

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  • Some aspects of generator backup protection in relation to synchronous-machine performance during h.v.-system faults

    Publication Year: 1972 , Page(s): 865 - 870
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (673 KB)  

    The fault performance of large generator units is considered in relation to the selection of generator-backup-protection settings, and a method of determining protection performance is presented, based on a simplified analysis of generator fault currents and neglecting rotor-angle swings. The validity of this approach is demonstrated and the method is used to determine the fault performance of negative-phase-sequence current and overcurrent protection. Alternative methods of overcurrent protection are examined which appear to provide improved backup protection for internal and external faults. View full abstract»

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  • Unification of field and circuit theories of electrical machines

    Publication Year: 1972 , Page(s): 871 - 876
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (782 KB)  

    The field in the airgap of an idealised model induction motor is derived from Maxwell's equations, and the result is extended to give the stator and rotor field equations of the practical machine. It is shown that, if each term of the voltage equation of the machine, referred to stationary axes, be multiplied by the quantity K = (1/2k1N1¿) sin p¿1 where N1 is the number of primary terms per phase, k1 is the distribution factor, ¿ is the axial length, in metres, and p is the number of pole pairs, each term of the field equation will be obtained. Since the voltage equation concerned applies generally to all types of machine, the unification also appears to be general. As an illustration of its consequences, the commutator (Park's) transformation of circuit theory is shown to be equivalent to the Lorentz transformation of field theory. View full abstract»

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  • Saturation and finite-length effects in solid-rotor induction machines

    Publication Year: 1972 , Page(s): 877 - 882
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (625 KB)  

    Taking both saturation and finite length into account, the authors derive the equivalent-circuit rotor impedance for an induction machine fitted with a solid, unslotted rotor. The analysis is based on the results of a previous analysis of finite-length effects, in which saturation was ignored. A picture is presented of the electromagnetic fields in a rotor of finite length, and an analysis is made by dividing the active region of the rotor into saturated and unsaturated parts. A comparison of theoretical and test results is made for a 10 kW induction motor. View full abstract»

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  • New temperature test for polyphase induction motors by phantom loading

    Publication Year: 1972 , Page(s): 883 - 887
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (681 KB)  

    A new temperature-test method for induction motors is described, in which two identical machines are connected electrically together, with their losses supplied externally. No other loading machine is required, nor have the test motors to be mechanically coupled. Experiments on laboratory-size machines have shown that the test simulates a true temperature run with a high degree of accuracy. View full abstract»

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  • Discussion on "Universal-burning linear tungsten-halogen lamps"

    Publication Year: 1972 , Page(s): 888 - 889
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  • Economic optimisation of equipment strength in stochastic environment

    Publication Year: 1972
    Save to Project icon | PDF file iconPDF (114 KB)  
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  • Rating of conductors for short-duration currents

    Publication Year: 1972 , Page(s): 891 - 892
    Save to Project icon | PDF file iconPDF (308 KB)  
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  • Magnetic permeance of identical double slotting

    Publication Year: 1972 , Page(s): 892 - 893
    Save to Project icon | PDF file iconPDF (277 KB)  
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  • Voltage surges induced on overhead lines by lightning strokes

    Publication Year: 1972 , Page(s): 893 - 894
    Cited by:  Papers (2)
    Save to Project icon | PDF file iconPDF (242 KB)  
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  • Comparison of alternative skew-effect parameters of cage induction motors

    Publication Year: 1972 , Page(s): 894 - 895
    Save to Project icon | PDF file iconPDF (280 KB)  
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  • Effect of skewing slots on flux distribution in induction machines

    Publication Year: 1972 , Page(s): 895 - 896
    Save to Project icon | PDF file iconPDF (322 KB)  
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  • Numerical methods of conformal transformation

    Publication Year: 1972
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The Proceedings of the Institution of Electrical Engineers was published by the IET between 1963 and 1979.

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