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Electrical Engineers, Proceedings of the Institution of

Issue 3 • Date March 1974

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Displaying Results 1 - 16 of 16
  • Linear antenna arrays with broadened nulls

    Publication Year: 1974 , Page(s): 165 - 168
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (545 KB)  

    It is shown that a null in the radiation pattern of a linear antenna array can be broadened into a null sector by the use of suitable forms of amplitude taper. For a uniformly spaced array, binomial taper coefficients with alternate positive and negative signs produce a maximally-flat null broadening. Null slewing by means of phase taper and null broadening by means of amplitude taper can be regarded as two independent operations. View full abstract»

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  • Use of sample-and-hold delay circuits for synthesis of raised-cosine filters

    Publication Year: 1974 , Page(s): 169 - 172
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (431 KB)  

    A new technique is described in which f.e.t. sample-and-hold delay circuits are used to shape a square-wave digital pulse into a pulse whose spectrum approximates to a raised-cosine spectrum with 100% roll off. The technique, which is entirely digital, is examined both theoretically and experimentally, and it is found that the raised-cosine spectrum can be synthetised simply, and to a high degree of accuracy. The technique is easier to implement than methods based on conventional network synthesis. View full abstract»

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  • Analysis of d.c. chopper circuits by computer-based piecewise-linear technique

    Publication Year: 1974 , Page(s): 173 - 178
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (590 KB)  

    A computer-based method for analysing the performance of d.c. chopper circuits is proposed. In the paper, a piecewise-linear description is established by considering sequential circuit modes, defined by the switching action of thyristors and diodes. The method is quite general, and could be applied to any particular chopper circuit to provide both transient and steady-state performance data. As an illustration, the method is used to describe the performance of a d.c. series motor controlled by a chopper circuit that provides both armature and field control. Control characteristics of this circuit are established, and these are compared with practical results obtained by measurement on a 220 V, 8 A series motor. View full abstract»

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  • Modes of operation in convertor-controlled d.c. drives

    Publication Year: 1974 , Page(s): 179 - 183
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (642 KB)  

    The existing analysis of the convertor-controlled d.c. drive is suitable only for the operation of the system under certain conditions; it does not take into account some modes of operation that appear to have been overlooked in the past. This paper redefines modes of operation of the drive, and presents a modified analysis and a suitable method for solving the system equations. Although the analysis is confined to single-phase systems, a similar analysis would apply to more complex configurations. View full abstract»

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  • Balanced synthetic circuit: new circuit for high-power testing with low-frequency transient recovery voltage

    Publication Year: 1974 , Page(s): 184 - 190
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (951 KB)  

    A new circuit is proposed for high-power synthetic tests of circuit-breaker performance. The new circuit is based on the current-injection principle, and is especially suited to economical tests with low-frequency transient recovery voltage (t.r.v.). Tests are possible with virtually any combination of t.r.v. and injection conditions, including those in which the t.r.v. frequency is lower than the injection frequency. The usual interaction which takes place between the t.r.v. and injection circuits is fully compensated, and, if necessary, components can be used in the t.r.v. network which are identical with those that would be used in a direct test under the same conditions. However, the usual restriction applies that there be no direct-current path to earth, if the recovery voltages is to be maintained. Examples are given of test circuits meeting the IEC requirements for the most difficult case of duty at 100% rated current. View full abstract»

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  • Impulse performance of a tower for transmission at 1300 kV

    Publication Year: 1974 , Page(s): 191 - 196
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (750 KB)  

    As part of a programme of research on ultrahigh voltage (u.h.v.) lines, the impulse performance of a rig simulating the critical portion of a 1300 kV system transmission tower with 9.3 m clearance has been determined. Outcomes include the following: The minimum strength corresponds to a mean field of 230 kV m¿1, and occurs with positive polarity on the conductor and with a front time of about 350 ¿s. The minimum withstand level corresponds to 1.8 p.u. The time lags before breakdowns are given over the range of crest times 50¿750 ¿s. The effects of small changes in the dimensions of the rig were determined, and the performance was found to be relatively insensitive to these. A ratio of rig conductor length to gap spacing of 2.5:1 is shown to be adequate. Tests of the switching-impulse performance of the window were made over a period of one year, in a considerable variety of weather conditions, and negligible variations were found. View full abstract»

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  • Internal design of unlaminated-rotor induction machines

    Publication Year: 1974 , Page(s): 197 - 202
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (792 KB)  

    The internal design of unlaminated-rotor induction machines is investigated, with particular reference to hollow shell rotors either with or without a central steel web. The performance of these designs is explained in terms of flux-penetration, eddy-current and endeffect factors, and the theory is substantiated by measurements of machine performance and flux distribution. The examples given show that the webbed rotors can be designed to give either high torque or low inertia. View full abstract»

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  • IEE South-East Midland Centre, Rugby Area: Chairman's address. Review of economics of security of supply

    Publication Year: 1974 , Page(s): 203 - 204
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (153 KB)  

    First Page of the Article
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  • Restrictions on attainable poles and methods for pole assignment with output feedback

    Publication Year: 1974 , Page(s): 205 - 212
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1011 KB)  

    The paper establishes the restrictions on the attainable closed-loop poles in single-input systems when constant feedback is employed from an output vector of smaller dimension than the state vector. These restrictions are linear equations in the coefficients of the closed-loop characteristic polynomial, and are obtained from the matrices describing the system in the state-space form. The closed-loop pole specifications are then expressed as linear equations in the coefficients of the characteristic polynomial, and these are solved simultaneously with the constraint equation to obtain the output-feedback vector required for pole assignment. The results developed for single-input systems are then extended to multivariable systems where the output-feedback matrices used are restricted to have unity rank. Further, arbitrary pole assignment in multivariable systems using unity-rank output feedback is studied. A number of illustrative examples are given. View full abstract»

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  • Boundary probe for measurement of current density and electric-field strength - with special reference to ionised gases

    Publication Year: 1974 , Page(s): 213 - 220
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (790 KB)  

    An active probe is described that is suitable for measurement of current density J and electric-field strength E over an electrode boundary. It is capable of high mechanical resolution, since spatial accuracy of 0.5 mm is readily obtainable. Calibration of the probe is in terms of its mechanical dimensions, so that J may be determined to within ±1%, and E to within ±5%. The measurement of E is dependent on those situations where the motion of carriers is due to electrical drift; so that, in gases, the mean free path of ions should be less than a probe diameter. No such restriction applies to J. The probe has an interesting characteristic that is shown to have considerable generality in ionised air at s.t.p. It may prove to possess much wider generality. The method is presented and verified for static fields. Gaseous discharges and electrolytes may be usefully examined, and their conductivity measured directly. View full abstract»

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  • Effect of humidity on sparkover of airgaps under impulsive voltages

    Publication Year: 1974 , Page(s): 221 - 222
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    The influence of high humidity on the sparkover of a 40 cm square-ended rod-rod gap and round-ended rod-plane gap has been studied using impulse voltages of +1/1000 ¿S waveshape. Over the large humidity range 7¿27 g/m3 achieved, it was found that, for each increase of 1 g/m3 of water vapour, a corresponding increase in the mean sparkover voltage of 1% for the rod-rod gap and 1.25% for the rod-plane gap was obtained. View full abstract»

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  • Electrical breakdown of N2O, SF6 and N2O/SF6 mixtures

    Publication Year: 1974 , Page(s): 223 - 226
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (491 KB)  

    Measurements of static breakdown voltages were made for SF6 and N2O/SF6 mixtures containing between 1% and 50% SF6 by volume for values of Nds within the range 1023 < Nds < 1024 m¿2 (where N is the gas number density and ds the sparking distance). These results, together with earlier data on N2O, show that the departures from Paschen's law become smaller as the percentage of SF6 in the mixture is increased over the range from 0 to 10% becoming negligible above about 6%. These results agree with predictions made on the basis of the ion-molecule reactions occurring in these gases. The dielectric strength of a 37% mixture was found to be about 83% of that for SF6 alone, and it is shown that, for this mixture, an increase in total pressure of about 20% gives the same dielectric strength as SF6 alone with a saving in cost of about 50%. View full abstract»

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  • Prebreakdown phenomena in transformer oil subjected to nonuniform fields

    Publication Year: 1974 , Page(s): 227 - 231
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (830 KB)  

    These investigations were conducted to record Schlieren photographs of the prebreakdown phenomena in transformer oil subjected to nonuniform fields at room temperature and atmospheric pressure. Various states of contamination were also studied. Positive and negative voltage polarities were used, and an estimate of the disturbance temperature was made by measuring changes in refractive index. Breakdown was initiated by disturbance channels propagating from the point electrodes; the positive-point disturbance being more filamentary and propagating much faster. The propagation rate increased when contaminated by solid particles, the effect being enhanced by prestressing. No significant change was detected with dissolved air or oxygen. However, when either gas was added to oil containing solid particles, the propagation rate tended to decrease after prestressing. The disturbances consisted of a liquid at a higher temperature than the surrounding bulk. It was suggested that the disturbances contained significant net space charge, which distorted the applied field and which was propagated by electron-collision processes. The effect of solid particles was explained by local field enhancement and the effect of prestressing by the motion of particles into or away from regions of strong field. View full abstract»

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  • IEE Irish Branch: Chairman's address. Broadcast engineering: past, present and future

    Publication Year: 1974 , Page(s): 232 - 233
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (402 KB)  

    First Page of the Article
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  • IEE Southern Centre, Eastern Area: Chairman's address. Management of men and materials

    Publication Year: 1974
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (145 KB)  

    First Page of the Article
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  • Electrically induced mechanical oscillations in plane-electrode system

    Publication Year: 1974 , Page(s): 235 - 236
    Save to Project icon | PDF file iconPDF (214 KB)  
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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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