By Topic

Electrical Engineers, Proceedings of the Institution of

Issue 6 • Date June 1975

Filter Results

Displaying Results 1 - 25 of 25
  • Coupled parallel rectangular dielectric waveguides

    Page(s): 593 - 599
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    The method of adiabatic invariance of action applied to electromagnetic resonators is used in the analysis of coupling between rectangular dielectric rods. The field values used in the analysis are obtained by a point-matching technique. The results are supported by experiments. For a certain configuration, an almost linear dependence of coupling coefficient on frequency is found over a wide range of frequencies. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Investigations of attenuation by rainfall at 110 GHz in south-east England

    Page(s): 600 - 604
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (613 KB)  

    Observations for one year over a 2.65 km path have yielded distributions with time of the depth of fading, duration of fading and the time between fades, and information on the weather situations producing rain which gives high attenuation. Observed attenuation has also been related to rainfall rate at a point. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design method for interferometer array. Measurement of the elevation angle of waves in the presence of a reflecting terrain

    Page(s): 605 - 608
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    A design method is given for interferometer arrays that are required to measure the elevation angle of arrival of waves in the presence of near-horizontal specularly-reflecting ground, The array consists of a number of interferometers of different baselines whose phase measurements are used together to compute the elevation angle; only the fractions of cycles of phase are measurable and the constraints include size and cost. The design method considers the disposition of the individual interferometers and the way the elevation angle is computed from the phase measurements. The objective is an accurate estimate of elevation angle over a wide range of angles. The possible improvements that might result from measurements of amplitude as well as phase have been considered. One application might be to aircraft landing aids to improve the present international landing system (i.l.s.). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Net coding gain of error-correcting codes

    Page(s): 609 - 614
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (804 KB)  

    The paper introduces the concept of `net coding gain¿ as a measure of the effectiveness of error-control systems. It attempts to express the improvement attained by coding in terms of effective signal/noise ratio, so that the effect of coding can be compared with other expedients, such as increasing the power per bit. Theoretical and experimental results are given to show how net coding gain depends upon system parameters such as mean signal/noise, block size, and redundancy. The experimental results show how interleaving can overcome the effect of correlation between errors. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Technique for realising transversal filters using charge-coupled devices

    Page(s): 615 - 619
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (728 KB)  

    The development of a technique for the nondestructive sensing of the signal charge propagating in a c.c.d. structure is described. An analysis of the sensing circuit is performed, particular attention being paid to the nonlinearities inherent in the charge-sensing method. The noise properties of the circuit are discussed, together with other parameters such as transfer efficiency, charge-handling capability, and tap-weighting errors, relevant to the use of c.c.d.s in systems applications. Finally, a prototype matched-filtering subsystem is described which utilises this tapping technique in the generation and correlation of a 13 bit Barker-coded sequence. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High-accuracy cathode-current calculations in computer simulations of electron guns

    Page(s): 620 - 624
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (793 KB)  

    The outline of a method of electron-gun iterative analysis by computer is given, with particular emphasis on improved methods for cathode-current-density calculations. It is shown how the effects of cathode curvature, magnetic fields at the cathode surface, etc. can be taken into account in estimating the emission currents. Numerical results are compared with those of several previously-published computer analyses. It is also shown how 4th-order correction terms can be included in the finite-difference equations to improve the accuracy of results obtained using coarser meshes. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modelling approach to the design of thyristor systems

    Page(s): 625 - 629
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (531 KB)  

    The paper describes the use of modelling techniques in the design of practical thyristor-machine systems. Digital modelling techniques are also discussed in relation to computer simulation of such schemes. The approach is treated with reference to a simple single-phase/3-phase cycloconvertor, but the paper illustrates that the methods are of wide application. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Three-phase bridge rectifiers with complex source impedance

    Page(s): 630 - 636
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (682 KB)  

    The operation of uncontrolled and controlled 3-phase bridge rectifiers with resistive and inductive source impedances is investigated. Equations describing the operation of the systems, from open circuit to short circuit on the d.c. side, are given. Results computed from these equations are presented in graphical form. The effect of varying the ratio of source resistance to reactance is demonstrated. Some experimental results obtained from a model system are presented. From the results, it is shown that the resistive component of the source impedance will have a significant effect on the operation of a rectifier system, unless the source reactance is at least an order of magnitude greater than the source resistance. Resistive components of the source impedance have their greatest impact on the high voltage/low current portion of the load characteristic. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characteristics of a diode-bridge-loaded synchronous generator without damper windings

    Page(s): 637 - 642
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (641 KB)  

    The paper extends the theoretical study of diode-bridge-loaded synchronous generators without damper windings to loads with commutation angles equal to or greater than 60° (modes 2 and 3). The equations necessary to establish the performance in these operating modes, and a simple method of establishing the boundaries between the modes, are given. Constant flux linkages are assumed. Experimental results from tests on a 5 kVA laboratory generator have been used to check the computed theoretical results obtained by using the published equations. A larger, turbogenerator exciter has been used to illustrate the theoretical difference between operation in mode 1 and mode 2. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimisation program for large-induction-motor design

    Page(s): 643 - 646
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (642 KB)  

    The problem of designing large induction motors at a minimum cost is approached using nonlinear programming. The performance evaluation programs include saturation effects, stray load losses, and airflow and temperature rise throughout the machine, while the cost function includes labour as well as material costs. A new optimisation technique is employed which promises rapid convergence and allows the program to begin from, and search through, nonfeasible designs. This feature eliminates the need for a synthesis program as required in most optimisation methods. The program has been applied to motors in the range of 148¿1 110kW. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Calculation of reswitching surge current in an induction motor

    Page(s): 647 - 649
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    The paper investigates the transient phenomena in an induction motor after reswitching. It is assumed that prior to reswitching a current flows in the rotor winding. The maximum peak value of the transient current does not occur if the voltage induced by the rotor current and the supply voltage are in phase at the instant of reswitching. The conditions for both the severest and the most advantageous reswitching transients during the first period after reswitching are examined. By using special, but now known, devices built into autoreclose circuit breakers, it is possible to perform reswitching under the most advantageous conditions. This leads to a considerable reduction of stator surge current. In the case of an 8200 kW motor, mentioned in the paper, the surge current at 0.7 synchronous rev/min can be limited to 2 p.u. instead of 18 p.u., which occurs in the most severe case. This reduces electrodynamic forces acting on stator end windings. Since the forces are proportional to the square of the reswitching current, their reduction (1:81) in the above mentioned example prevents end-winding insulation breakdowns caused by dangerous mechanical vibration during reswitching. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experimental study of pole-changing series motors

    Page(s): 650 - 651
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (247 KB)  

    A series motor (single phase or 3 phase) having an armature winding with cross connectors permits a 2nd-pole operation for its rotor as an induction cage. Experimental investigations reveal that the preferred 2nd pole is a lower one. Six terminals are required for 3-phase and 4 for single-phase machines. With no additional winding in their stators, pole-changing windings in these machines provide an additional constant-speed characteristic besides a series one. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Canonic-form realisation from general input-output data

    Page(s): 657 - 662
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (582 KB)  

    A method is developed for attacking the problem of realising a linear discrete-time multi-input/multi-output system from input-output data. In addition to providing a framework for revealing the relation between previous approaches to this problem, the approach used here brings out several new aspects which enable the development of an efficient algorithm. This efficiency is made possible through the careful use of canonic system matrices View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimal smoothing in the identification of linear time-varying systems

    Page(s): 663 - 668
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (820 KB)  

    Several recursive methods are available for the estimation of linear time-varying process models from sampled input/output records. During convergence from poor initial estimates, they give no clear picture of the time variation. A remedy is to base the estimate at every point in time on the whole record, by use of optimal smoothing techniques originally developed for state estimation. Optimal smoothing algorithms are reviewed and their computational requirements and stability in an identification context are examined. The most attractive are tested on synthetic records and on hydrological records. It is concluded that they are feasible and effective. Examples are given of features revealed by optimal smoothing, but not by the usual identification techniques. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • IEE Conference Publication 127. Trends in online computer-control systems

    Save to Project icon | PDF file iconPDF (172 KB)  
    Freely Available from IEEE
  • Magnetically driven arcs with combined column and electrode interactions

    Page(s): 669 - 671
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (381 KB)  

    In recent years, it has been found possible to correlate both the magnetic and electric characteristics for many magnetically deflected arcs. This paper shows however that large departures from the magnetic characteristics can occur. Experimental results up to arc currents of several thousand amperes, arc lengths of 11 mm and gas pressures of 11 atm indicate factors that can lead to unexpectedly slow arc movement, which may be unsatisfactory in circuit-breaker applications, both in adversely affecting the interrupting ability and because of contact damage. Indications have been found that the inadequate movement is not necessarily caused only by electron emission or arc-column friction effects, and that electrode-vapour jets are probably involved View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Factors affecting the electrical characteristics of electrostatic precipitators

    Page(s): 672 - 674
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (362 KB)  

    The paper discusses some characteristics of the voltage and current flowing in an electrostatic precipitator during normal and abnormal operation. Although the waveform of the corona current in the airgap cannot be measured, it is shown that this may be calculated from the external voltage and current waveforms. For high-resistivity particulates, the current at normal operating conditions may contain a significant proportion of positive-ion current due to the effect of the back corona. This does not contribute to the particle collection, and, if excessive, it will have deleterious effects. Its presence may be detected by the discontinuity in the voltage/current characteristic. The resultant current transient due to a spark is analysed and is shown to comprise four separate components. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Voltage-transformer testing-set calibrator

    Page(s): 675 - 680
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (674 KB)  

    A direct-reading instrument for the precise calibration of voltage-transformer testing sets of the comparator type is described. The calibrator covers a range of ±11.11% for voltage error and ±411 min for phase error. These quantities are indicated on decade dials with constant resolutions of 0.001% and 0.1 min, respectively. The accuracy depends on the indicated voltage errors and phase errors, but is well within the resolution limits of most commercially available testing sets. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Three-dimensional numerical solution of eddy currents in thin plates

    Page(s): 681 - 688
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (904 KB)  

    Numerical methods of solving eddy-current problems are difficult to apply to 3-dimensional fields, because all the field quantities are vectors, with three components, and the electrostatic field generated by the conductor surfaces has to be taken into account in magnetic-vector-otential formulations. By treating the linked current and flux paths in network terms, it is shown that all linear and nonlinear 3-dimensional problems can be expressed in terms of two scalar functions, and that, when the currents are confined to thin conducting layers, this reduces to a magnetic-scalar-potential formulation. The network approach expresses this, simply and directly, in numerical terms. It can be readily extended to include eddy currents in iron surfaces, and to thicker conductors in which the magnitude and phase of the induced currents varies with depth. Circuits consisting of small-diameter wires can be treated in terms of an equivalent plate with a discontinuous conductivity. The calculated field distribution round a square copper plate, solved iteratively, has been found to converge rapidly and to give results in close agreement with values obtained experimentally. The method has been applied to transformer-legplate and core losses View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

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

Full Aims & Scope