Scheduled System Maintenance:
Some services will be unavailable Sunday, March 29th through Monday, March 30th. We apologize for the inconvenience.
By Topic

Electrical Engineers, Proceedings of the Institution of

Issue 4 • Date April 1978

Filter Results

Displaying Results 1 - 21 of 21
  • Microwave modelling of h.f. Yagi antennas over imperfectly-conducting ground

    Publication Year: 1978 , Page(s): 261 - 266
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (710 KB)  

    Yagi antennas Operating at 25 MHz over real ground have been modelled at microwave frequencies. The method of modelling ground, the measurement of its electrical parameters and the apparatus for measuring radiation patterns of model antennas are described. Typical radiation patterns thus obtained are compared with those predicted from theory. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Frequency multiplication using field-effect transistors

    Publication Year: 1978 , Page(s): 267 - 268
    Save to Project icon | PDF file iconPDF (216 KB)  
    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Parametric oscillatory motion in electromechanical devices

    Publication Year: 1978 , Page(s): 269 - 277
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (993 KB)  

    An analysis is presented which explains the mechanism of parametric motion in electromechanical devices. The implications of the mechanism, in the unstable operation of a wide range of electrical machines, are indicated; for example, in stepper motors where, under certain combinations of system parameters and operating conditions, oscillations superimposed on the synchronous rotary motion are observed. The simplest possible device in which parametric oscillations occur, the magnetically-maintained pendulum, is considered in detail and the conditions necessary for maintenance of motion are given. Expressions are derived for (a) the boundary frequency above which the damping torque is negative, and (b) the frequency at which peak negative damping occurs. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electromagnetic field diffusion in ferromagnetic materials

    Publication Year: 1978 , Page(s): 278 - 282
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (559 KB)  

    The diffusion of electromagnetic fields under pulse excitation in ferromagnetic materials is investigated using finite-difference techniques. The nonlinearity of the magnetisation curve is taken into account, and special attention is given to high saturation. The diffusion in the semi-infinite space is studied for various waveshapes and for different field intensities. For electromagnets with rotational symmetry, flux-density distributions and eddy-current losses are computed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multilayer approach to the analysis of single-sided linear induction motors

    Publication Year: 1978 , Page(s): 283 - 287
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (531 KB)  

    Among linear electric motors, single-sided linear-induction motors (s.l.i.m.s) with sheet on solid-back-iron secondary have been generally preferred for low-speed drives and, in the last few years, they are considered one of the most probable alternative for the propulsion of some of the medium and high speed vehicles of the near future. Although a precise assessment of the performance of s.l.i.m.s is necessary, this seems to be a difficult task because of the presence of longitudinal-, and transverse-edge effects together with skin, and saturation effects in the back iron of the secondary. The literature in the field ignores one or two of the above mentioned phenomena. The present paper strives to present a complete theory of s.l.i.m.s and at the same time takes into account the specific phenomena mentioned earlier. The theory is based on the double Fourier series decomposition of the primary magnetomotive force (m.m.f.). The back iron of the secondary is notionally split into thin sheets of constant permeabilities which are determined by means of an underrelaxed iterative procedure. The theory has shown good agreement with results obtained from tests performed on an arch-type primary with a large diameter-wheel secondary. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Hysteresis motor with overexcitation and solid-state control

    Publication Year: 1978 , Page(s): 288 - 292
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (541 KB)  

    The overexcitation for a short period of a hysteresis motor when running synchronously gives a reduction in stator current and an increase in pull-out torque. The physical concept of the phenomenon is briefly discussed and an empirical equivalent circuit incorporating a residual flux voltage is established which gives reasonable agreement with measured values. Methods of implementation of the technique are described, including delta-star starting and two solid-state-control devices. It is shown that, with short-duration overexcitation, harder magnetic materials may be used for the rotor, thus increasing the machine rating for a given frame size. View full abstract»

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

    Publication Year: 1978 , Page(s): 293 - 297
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    A new algorithm has been developed for fast-transient-stability studies, by decoupling the machines from each other and suitably modifying the electrical output to take into account the effect of the rest of the system. Apart from speed, this gives additional information about the quality of stability of the system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simulator for studying operational and power-supply conditions in rapid-transit railways

    Publication Year: 1978 , Page(s): 298 - 303
    Cited by:  Papers (11)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (751 KB)  

    The paper describes the development of a computer-based simulator which may be used to study the relationships between train movements and power-supply conditions in a 2-road rapid-transit railway. The work was specifically undertaken to enumerate the energy saving consequent on the introduction of chopper-controlled traction-control equipment with regenerative-braking capability. In the simulator, track topology and signalling constraints are represented by a sequential block structure which is analogous to the fixed-block signalling arrangements. Tractive characteristics of the traction equipment are represented by models which are train speed and line voltage dependent. Powering and braking trains are represented by piecewise linearised models and a complete power-network solution is obtained at each update period. The simulator is written in extended Fortran IV and is reasonably efficient in computer processing time; e.g. running a 1 h service at 90 s headway on a 5 km section of track typically requires 4 min of central processor time on an ICL 1906A. Simulating 20 km of double track, with up to 100 trains per track, typically requires 36 Kwds of core. Although the simulator was developed specifically for energy-consumption calculations, the methods of representation are quite general. The simulator may thus be used to study other problems of interest in train performance and signalling studies. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simulation studies of energy saving with chopper control on the Jubilee line

    Publication Year: 1978 , Page(s): 304 - 310
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1000 KB)  

    The paper describes energy-consumption studies undertaken for the operation of rapid-transit services on London Transport's new Jubilee line. The object of the studies was to provide comparative figures for the energy consumption of a chopper-controlled fleet and a conventionally equipped rheostatically-controlled fleet. The work was undertaken using a digital computer simulator in which train movement and power-network calculations are interdependent. This approach permits the evaluation of system constraints when regenerative braking is used in conjunction with the usual, plain diode, noninverting type of substation. Detailed figures are provided for various services operating on a short 5 km isolated power block section of the line and also for peak and off-peak services on the whole line. Sensitivity experiments on this 5 km section demonstrate the dependence of energy reduction on the opportunities to transfer energy between trains, on the line voltage limit and on the traction equipment specification. For whole line operation, at peak and off-peak headways, the energy savings are 15% and 9% respectively. These figures reflect the use of a low characteristic traction motor and the moderate proportion of braking energy actually available for potential regeneration (52% of total braking effort for an average loaded train). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Use of London's electricity supply system for centralised control

    Publication Year: 1978 , Page(s): 311 - 327
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3066 KB)  

    The paper reviews the pioneer work carried out by the London Electricity Board, leading up to the installation of a mains-borne signalling system for off-peak load switching in a large council housing development in the London Borough of Brent. It shows how technical liaison between a manufacturer and an area board has contributed to the evolution of a secure and viable scheme. Sensitivity and stability are discussed using different signalling methods that employ solid-state devices to modify the 50 Hz waveshape. Results of the trials on interconnected and radial low voltage supply networks are presented, indicating that the type of urban low voltage (l.v.) supply is unlikely to affect the efficiency of the signalling systems. An improved signalling technique, proposed by GEC Measurements and used in the Brent installation, is described. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Evaluation of p.w.m. inverter schemes

    Publication Year: 1978 , Page(s): 328 - 334
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (829 KB)  

    The paper surveys the various pulse-width-modulation schemes used in thyristorised inverters. The practical problem of choosing the two variables, frequency-modulation index M and depth of modulation ¿, which determines the output waveshape of the p.w.m. inverter, is also discussed. An algorithm is given to select the values of M and ¿ to obtain minimum low-order harmonics. Some sample results for various cases have been tabulated. The algorithm can be used to extend the range of variables to other values of practical interest. The results so obtained will be of use to a designer in evaluating the various p.w.m. schemes that are feasible. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Economic load-dispatch solution using fast-decoupled load flow

    Publication Year: 1978 , Page(s): 334 - 335
    Save to Project icon | PDF file iconPDF (252 KB)  
    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Winding grading of single-phase induction motors

    Publication Year: 1978 , Page(s): 335 - 336
    Save to Project icon | PDF file iconPDF (219 KB)  
    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Canonical form for the reduction of linear scalar systems

    Publication Year: 1978 , Page(s): 337 - 342
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (693 KB)  

    Consideration is given to the problem of the reduction of order of a scalar system S(A, B, C) described by a transfer function g(s). On the assumption that the reduced-order model is to be used for feedback control-systems design, a canonical form is derived equivalent to a system decomposition related to the asymptotes, intercepts and finite zeros of the system root locus. A model reduction procedure based on the canonical form is suggested and shown to be capable of providing a good approximation to both the dominant poles and dominant zeros of g(s) and to make possible the matching of the desired number of high and low frequency moments. The canonical form can also be used to provide an estimate of a suitable reduced-model order. Two examples are described. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design of a dynamic output-feedback compensator

    Publication Year: 1978 , Page(s): 343 - 345
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (334 KB)  

    A dynamical system in the usual state space form is augmented with a series connection with another dynamical system of calculable order. A state-feedback controller is then designed for the compound system. A method is then given which designs a dynamically equivalent output-feedback system. Feedforward matrices can then be added to achieve static decoupling of some states and outputs. An illustrative example is given. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • New method of deriving equivalence conditions in linear diffusion equations

    Publication Year: 1978 , Page(s): 345 - 346
    Cited by:  Papers (1)
    Save to Project icon | PDF file iconPDF (178 KB)  
    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Lightning and tall structures

    Publication Year: 1978 , Page(s): 347 - 351
    Cited by:  Papers (12)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (835 KB)  

    The mechanism by which lightning is attracted to an earthed structure of low height is well established, and the distances over which strokes of different intensities are attracted (the so-called striking distances) have been determined. It appears that the numerical values so established do not apply to structures exceeding, say, 20m in height. In the electric field under a thundercloud, tall structures produce point-discharge currents. Field observations have shown that the resulting space charges can assume the same shape as the visible plume of smoke from a chimney. When a normal negative leader approaches such a positively charged `plume¿, it will be attracted to it, and unusually long `striking distances¿ can result. A plume of positive space charge may be broken up by the action of the violent updrafts and downdrafts under an active thundercloud. The resulting pockets of space charge in the atmosphere are held responsible for the branching of earth flashes. They may also be responsible for strikes to points well below the tips of tall structures standing on open ground. On the other hand, it is suggested that structures surrounded by other tall structures or trees are subject to roughly the same striking distances as low structures. It is furthermore suggested that present knowledge is inadequate to determine striking distances for the less frequent positive discharges. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Light emission and deterioration in epoxy resin subjected to power frequency electric fields

    Publication Year: 1978 , Page(s): 352 - 354
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (594 KB)  

    Light emission from an epoxy resin specimen with pin-plane electrodes was studied using a refrigerated 13-stage photomultiplier and a 4-stage image intensifier. In the pretreeing period weak light, comparable in intensity to that resulting from thermal photomultiplier noise, was observed together with visible effects of deterioration such as fine shadow lines and void formation and growth. The deterioration in the void-free state is probably caused by hot electron bombardment of resin molecules in the high field region. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wattmeter for some common requirements

    Publication Year: 1978 , Page(s): 355 - 358
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    The paper describes the background requirements and development work leading to the production of a low cost static wattmeter for use in educational establishments. Initially it was envisaged that the new wattmeter would have some industrial applications and these aspects are described, although no development has been done as yet. The form of the paper follows the growth of the new wattmeter from initial specification to its developed form. The work has been controlled throughout by the need to produce a simple instrument, which, although not a complete replacement for the dynamometer type, can nevertheless be used in many circumstances where the precision and expense of the dynamometer is unnecessary. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Turbulence in high-current arcs

    Publication Year: 1978 , Page(s): 359 - 360
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (274 KB)  

    Analysis of published experimental results of axial distrubution of the central plasma velocity of free-burning arcs, at currents of 500 A to 2.16 kA, indicates that turbulent exchange processes are dominant. The derived turbulence parameter using Prandtl's mixing-length theory is seven times larger than the only value previously estimated from the measurements of arc parameters. However, our value is in good agreement with previous results for compressible gas glow and plasma jets. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Surface-discharge-initiated breakdown in solid dielectrics immersed in high-pressure gaseous mixtures

    Publication Year: 1978 , Page(s): 361 - 363
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (439 KB)  

    Preliminary results of investigations into the characteristics of anomalous breakdown phenomena in synthetic solid insulating materials immersed in gaseous mediums and subjected to alternating voltages are reported in this paper. The breakdown voltage of the solid dielectric was found to decrease with increasing gas pressure. In a medium of a gaseous mixture of CCl2F2 and N2, the solid breakdown voltage was also noticed to increase with increasing percentages of nitrogen. 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