Your browser does not support JavaScript!
http://iet.metastore.ingenta.com
1887

Proceedings of the Institution of Electrical Engineers

Volume 121, Issue 10, October 1974

Volumes & issues:

Volume 121, Issue 10

October 1974

Design of precision rectifiers using operational amplifiers
Synthesis of high-stability 4th-order single-sideband crystal lattice filters
  • Author(s): J.K. Stevenson
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1045 –1050
  • DOI:  10.1049/piee.1974.0246
  • Type: Article
  • + Show details - Hide details
  • p. 1045 –1050 (6)
    A lowpass antimetric ladder network is transformed into a single-lattice single-sideband crystal filter using simple network equivalences and an asymmetrical frequency transformation. A methodis then given for altering the phase shift independent of both the attenuation and network configuration, and applied so that a crystal in each lattice arm resonates at the frequency of infinite attenuation. Transferring these crystals to outside the lattice results in single-sideband filters of high stability. A frequency transformation involving two attenuation poles is given in an Appendix.
    Add to favourites
    Export citations
Power reciprocity in antenna theory
  • Author(s): A.T. de Hoop  and  G. de Jong
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1051 –1056
  • DOI:  10.1049/piee.1974.0247
  • Type: Article
  • + Show details - Hide details
  • p. 1051 –1056 (6)
    A rigorous derivation of the power-reciprocity theorem in antenna theory is presented. It relates the absorption cross-section of the load in the receiving situation to the power gain of the antenna in the transmitting situation. The most general case is considered, namely (a) the materialof which the antenna is made may be lossy, anisotropic and inhomogeneous, if only linear in its electromagnetic behaviour, (b) the vectorial amplitude radiation characteristic of the antenna in the transmitting situation and the incident plane wave in the receiving situation may be arbitrarily elliptically polarised, and (c) the impedance of the load in the receiving situation may be arbitrarily mismatched to the input impedance of the antenna in the transmitting situation. Therefore the known, restricted form of the theorem is generalised; also some notions are made more precise. As a corollary, a generalised theorem is presented as to the average value of the absorption cross-section of the load taken over all directions of incidence.
    Add to favourites
    Export citations
Transmission loss in a waveguide partially filled with dielectric
Frequency control using binary rate multipliers for automatic testing on c.w. radar systems
  • Author(s): R.W. Levinge
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1059 –1066
  • DOI:  10.1049/piee.1974.0249
  • Type: Article
  • + Show details - Hide details
  • p. 1059 –1066 (8)
    R.F. signals with certain defined characteristics have to be generated for ground testing on f.m. c.w. radar airborne-guidance systems. Normally in flight, two r.f. signals would be received; one direct from the ground transmitter and the other originating at the same transmitter, but reflected from a target. A lowfrequency wide-deviation frequency modulator is applied to the carrier at the ground transmitter. Owing to a difference in the path lengths of the two signals, a difference in phase angle of the modulating signal results, and, owing to the Doppler effect, the carrier frequencies are slightly separated. For testing therefore two r.f. signals with a precise and variable difference frequency have to be generated. Also both signals must be frequency modulated at the same frequency to the same deviation, but with a variable phase angle between the two modulating signals. For this purpose, a study has been made of the behaviour of binary rate multipliers used partly to shift the frequency, and partly to frequency modulate the r.f. carriers. A common crystal oscillator would feed into two b.r.m.s each shifting the carrier by a different amount, and each frequency modulating the shifted carriers with the same deviation. The b.r.m. operates by removing pulses from an uninterrupted pulse train according to the digital address. Thus the mean output frequency is lower than the input, but is contaminated with phase jitter. Jitter magnitude varies considerably with the address pattern, and it increases with the number of address lines. A graph of maximum jitter is given for increasing numbers of address lines up to 13. It isshown how phase jitter may be reduced to an acceptable limit, and how a system to meet the requirements may be designed.
    Add to favourites
    Export citations
Hybrid decoding for digital-communication-feedback systems
  • Author(s): J.R. Edwards
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1067 –1075
  • DOI:  10.1049/piee.1974.0250
  • Type: Article
  • + Show details - Hide details
  • p. 1067 –1075 (9)
    Forward error correction (f.e.c.) and decision feedback (a.r.q.) are combined using a hybrid decoding scheme of partial error correction and partial error detection. This is shown to have advantages when a low error probability is required and efficient use of transmitter power is important. The performance of the scheme is analysed, assuming transmission over a channel disturbed primarily by white Gaussian noise. Results are presented for systems employing various BCH codes showing the effects on system performance of varying code length, code ratio, and of varying the maximumerror weight the decoder is allowed to correct. The hybrid scheme is shown to need less transmitter power than systems using either pure forward error correction or decision feedback with error detection alone, although the ability to reject error bursts is retained. A design procedure for choosing the code parameters and maximum error-correcting weight is given, and one method of implementing the decoding is suggested.
    Add to favourites
    Export citations
Computer-controlled queuing system with switching network and blocked customers rejoin end of queue
Computer-controlled queuing system with feedback and swap times
  • Author(s): W.K. Chung
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1080 –1085
  • DOI:  10.1049/piee.1974.0252
  • Type: Article
  • + Show details - Hide details
  • p. 1080 –1085 (6)
    The paper presents a detailed investigation of a computer-controlled queuing system with Poisson input, multiple exponential servers, first-come first-served queue discipline, feedback and fixed finite swap times. The swap time is the time needed for the allocated server to acquire necessary information about the customer to be served and set up a necessary connection. A generating function for the stationary state probabilities of, and the necessary and sufficient condition for, the existence of statistical equilibrium for the system are derived. Further, a formula for the determination of the waiting-time distribution in the system is obtained by the use of the theory of Markov chains.
    Add to favourites
    Export citations
Note on digital-summation threshold-logic gates
IEE Conference Publication 114. Electromagnetic-wave theory
Generalised analysis of machine windings, impedances and generated e.m.f.s, with particular reference to multispeed synchronous machines
  • Author(s): P.J. Lawrenson  and  S.R. Murthy Vamaraju
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1089 –1098
  • DOI:  10.1049/piee.1974.0255
  • Type: Article
  • + Show details - Hide details
  • p. 1089 –1098 (10)
    The paper extends previously available results for the calculation of airgap flux densities, generated e.m.f.s and synchronous impedances for all types of salient-pole or segmented synchronousmachines. Special emphasis is placed on multispeed machines, both excited and unexcited, but results for single-speed machines are included as particular cases. Nonidentical phase windings are treated as is necessary for practical multispeed machines. The needs to allow, in fundamental-frequency power calculations, for pulsations in the magnetic potentials induced on the rotor, and for differences in phase associated with the different harmonics, are brought out and treated for the first time. Earlier studies of various types of single- and multispeed reluctance machines are correlated in the context of the generalised results presented.
    Add to favourites
    Export citations
Linear induction motors as ‘electromagnetic rivers’
  • Author(s): J.F. Eastham  and  E.R. Laithwaite
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1099 –1108
  • DOI:  10.1049/piee.1974.0256
  • Type: Article
  • + Show details - Hide details
  • p. 1099 –1108 (10)
    Conducting material, in both the solid and the liquid state, can be suspended above a.c. coil systems. It is shown how a rectangular plate, suspended by one such system, may also be propelled by the same system of currents which serve to suspend it, and that lateral guidance is then automatically built into the system. In early experiments which are described, over 90% of the input power to such a system was converted into heat in the process of suspension and guidance. Further inventions are then described, by means of which it is theoretically possible to convert the whole ofthe secondary input power to propulsion. It is concluded that such systems show promise for application to high-speed ground transport.
    Add to favourites
    Export citations
Use of surface integral equations for analysis of TM-induction problem
  • Author(s): T.H. Fawzi  and  P.E. Burke
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1109 –1116
  • DOI:  10.1049/piee.1974.0257
  • Type: Article
  • + Show details - Hide details
  • p. 1109 –1116 (8)
    The problem considered is that of evaluating the induced fields and the power loss in a long conductor with arbitrary cross-section placed in a time-harmonic transverse magnetic (TM) field. Hitherto, the problem has been analysed by numerically solving the governing differential equations or a volume-type integral equation. The paper presents a new approach which uses Helmholtz single-and double-layer potentials to derive integral equations which relate the values of the axial current density and the tangential magnetic field at the surface of the conductor. These are two coupled Fredholm integral equations with weakly singular kernels. As an example, the eddy-current losses in a rectangular conductor placed in a uniform magnetic field are computed, and the results arecompared with previous ones. The proposed approach has two salient advantages. First, by reducing the dimensions of the problem by one, the computation time is considerably reduced. Consequently, many problems that are beyond the practical limit of previous approaches can be easily handled. Secondly, both magnetic and nonmagnetic conductors can be handled.
    Add to favourites
    Export citations
Equivalent circuits from electromagnetic theory low-frequency induction devices
Performance analysis of diecast multicage induction motors: a comparative study of two approaches
Calculation of saturation effects in segmented-rotor reluctance machines
Control of dual-excitation generator using derivatives of rotor angle
  • Author(s): R.K. Aggarwal  and  B.W. Hogg
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1134 –1140
  • DOI:  10.1049/piee.1974.0261
  • Type: Article
  • + Show details - Hide details
  • p. 1134 –1140 (7)
    The paper investigates the performance of a synchronous generator with two field windings, with separate voltage and angle regulators. The effects of continuous rotor velocity and acceleration feedback signals in the regulator loops are examined, and it is shown that different derivative gains must be used during steady-state and transient conditions to obtain the best performance. This is achieved by the introduction of some simple switching in the angle regulator, and is most effective when implemented at the peak of the first rotor-angle swing. Acceleration feedback is introduced in the governor system, and the results illustrate the significant improvements in transient performance which are possible with the fast governor systems which have been developed recently. Initial results were obtained by digital computer, and the proposed control schemes were then tested on a laboratory micromachine system.
    Add to favourites
    Export citations
Extension of stable operating regions of synchronous machines using low-sensitivity excitation control
  • Author(s): M.M. Elmetwally  and  N.D. Rao
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1141 –1145
  • DOI:  10.1049/piee.1974.0262
  • Type: Article
  • + Show details - Hide details
  • p. 1141 –1145 (5)
    In the usual design of optimal linear regulators for synchronous machines, the controller is designed for a particular set of system operating conditions. However, in actual system operation, these conditions are subject to load demands. Consequently, the optimal controller designed for a certain operating condition will no longer yield a satisfactory performance at others. The paper endeavours to overcome this problem by proposing a method for designing optimal controllers with low sensitivity to systemloading conditions, while avoiding the complexity of the resulting controller structure. A numerical example involving a synchronous machine swinging against an infinite busbar is used to demonstrat the usefulness of low-sensitivity controllers in extending the stable operating region.
    Add to favourites
    Export citations
Improvements in phase-controlled circulating-current cycloconverter using communication principles
Computerised linear control of a.c. generator power output
  • Author(s): W.S. Leung ; Y.S. Cheung ; Y.C. Yeung
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1150 –1154
  • DOI:  10.1049/piee.1974.0264
  • Type: Article
  • + Show details - Hide details
  • p. 1150 –1154 (5)
    The paper describes an online control system for regulating the power generation of an alternator that is connected to the supply Grid. The voltage, current and power factor of the a.c. generator are sampled and fed to the computer via analogue-digital convertors. The limits of the range of frequencies for sampling the input parameters to the computer are investigated, and an expression for the transfer function of the a.c. generator is derived. The input parameters are processed to produce the power, power angle and torque of the a.c. generator. The correcting signal from the computer is fed to the control field of a d.c. servomotor via a digital-analogue convertor. The servomotor in turn regulates the throttle opening of the petrol engine, which drives the a.c. generator. The piecewise linear method is used to approximate the relationship between the output of the a.c. generator and the throttle opening of the engine, and the technique of dynamic programming is used to optimise the overall system. Satisfactory results are obtained on an experimental system which regulates the output and stability of a 5 kVA petrol-engine/a.c. generator set.
    Add to favourites
    Export citations
Steady-state phase-variable model of the synchronous machine for use in 3-phase load-flow studies
  • Author(s): R.G. Wasley  and  M.A. Shlash
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1155 –1164
  • DOI:  10.1049/piee.1974.0265
  • Type: Article
  • + Show details - Hide details
  • p. 1155 –1164 (10)
    The derivation of a steady-state phase-variable model of the synchronous machine is considered for the purpose of investigating the influence of machine saliency on the unbalanced behaviour of powersystem networks. The model is particularly relevant as a means of representing the salient-pole generators of important hydroelectric stations feeding large and remote load centres. Application of the model is also considered so that corresponding blocks of the system Jacobian matrix are formulated and used in a previously described Newton — Raphson algorithm to obtain 3-phase load flows. The results of computation illustrate that saliency is not an insignificant parameter amongst those which determine the extent and distribution of system unbalance.
    Add to favourites
    Export citations
Computer-program description. Power-system dynamic-simulation program
Proposals for installation practice of single-core cables
  • Author(s): N. Foulsham ; J.C. Metcalfe ; S.E. Philbrick
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1168 –1174
  • DOI:  10.1049/piee.1974.0267
  • Type: Article
  • + Show details - Hide details
  • p. 1168 –1174 (7)
    A review of installation techniques has been undertaken for single-core power cables employed in the cable networks of industrial plant. Particular attention has been given to the performance of trefoilcable groups under short circuit, and the influence of the consequential electromagnetic forces on the supporting and securing system used to hold the cables. For the investigation, a series of short-circuit tests have been carried out, subjecting a range of typical cables to currents up to 44 kA. Based on these tests, proposals are made for securing cables using ties at spacings chosen over a range 0.3 m–1.2 m, with cleats spaced at 4 m and main supports at 2 m.
    Add to favourites
    Export citations
Damping of aeolian vibration on overhead lines by vibration dampers
Summary: Comparative performance of amplitude-comparator pilot-wire differential-protection systems
  • Author(s): C.B. Gray
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1180 –1182
  • DOI:  10.1049/piee.1974.0269
  • Type: Article
  • + Show details - Hide details
  • p. 1180 –1182 (3)
    A new relay circuit, applicable to asymmetrical pilot circuits, is described. In the steady state for relays at both ends, the circuit provides identical unit-diameter circular stability areas on the complex plane, centred on (1, 0), and it is suggested that this relay circuit constitutes a preferred characteristic of marginal operation. Certain alternative relay configurations are compared, to ascertain relative susceptibilities to the effects of induced interference voltages and the presence of d.c. components in the relaying quantities derived from the protected system. Homogeneous pilot circuits are assumed for simplicity, and the relay schemes considered include: (i) that referred to above which provides the preferred relay characteristic (ii) that which provides termination of the pilot circuit in characteristic impedance (iii) that which provides compensation for pilot-circuit phase-shift and a self-inverse characteristic.
    Add to favourites
    Export citations
Prediction of the parameters of an impulse generator for transformer testing
Erratum: Suggested definition of reactive power for nonsinusoidal systems
Erratum: Reactive-power definitions and power-factor improvement in nonlinear systems
Analysis of a class of nonlinear time-varying discrete systems using multidimensional parametric z-transfer functions
  • Author(s): V.S. Bansal  and  S.L. Mali
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1185 –1191
  • DOI:  10.1049/piee.1974.0273
  • Type: Article
  • + Show details - Hide details
  • p. 1185 –1191 (7)
    The paper presents a method of analysing a class of nonlinear time-varying discrete systems having polynomial-type nonlinearities. The analysis makes use of Volterra-series representation and multidimensional parametric z-transfer functions. The method is further extended to determine the output response between sampling instants through the use of multidimensional parametric modified z-transfer functions. The terminal-state theorems for multidimensional parametric z-transforms are presented. This new method of analysis is applied, for illustration, to a practical time-varying discrete system involving a nonlinear feedback element.
    Add to favourites
    Export citations
Impulse-voltage performance of contaminated surfaces
  • Author(s): G. Fabricatore  and  B. Macchiaroli
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1192 –1196
  • DOI:  10.1049/piee.1974.0274
  • Type: Article
  • + Show details - Hide details
  • p. 1192 –1196 (5)
    Tests were carried out to analyse the influence of geometrical and physical parameters, and of their uniformity, on the critical impulse flashover voltage of contaminated flat surfaces. As with alternating and direct voltages, the results show that the impulse flashover voltage depends strongly on the surface conductivity and slightly on the geometrical layer parameters. Comparison with results obtained on normal insulators demonstrates the possibility of carrying out research on small specimens, without limiting the effectiveness of resulting information; the only limit concerns the ‘saturation effect’, but this is because of the relatively short length of the specimens.
    Add to favourites
    Export citations
Vacuum breakdown between outgassed molybdenum electrodes
  • Author(s): D.W. Williams  and  W.T. Williams
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 10, p. 1197 –1200
  • DOI:  10.1049/piee.1974.0275
  • Type: Article
  • + Show details - Hide details
  • p. 1197 –1200 (4)
    Measurement of prebreakdown currents as a function of applied electric field have been made for polished molybdenum electrodes in ultra-high vacuum (≤ 10−8 torr). The prebreakdown currents have been measured (a) before and (b) after outgassing the electrodes separately at 600°C and then at 1000°C. The experimental data were analysed on the basis of the Fowler-Nordheim field-emission theory, and the breakdown voltage, the field enhancement factor, the onset current, the current density and the emitting area at breakdown are given as a function of the number of breakdowns. Results indicate that the breakdown voltage is increased by outgassing the electrodes and that anode outgassing is more important than cathode outgassing in obtaining a conditioned discharge gap with high breakdown voltage and low breakdown current. Exposing the electrodes to the atmosphere destroys the conditioned state of the electrode surface.
    Add to favourites
    Export citations

Most viewed content for this Journal

Article
content/journals/piee
Journal
5
Loading

Most cited content for this Journal

We currently have no most cited data available for this content.

Print this page
This is a required field
Please enter a valid email address