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Volume 126
Issue 5
Proceedings of the Institution of Electrical Engineers
Volume 126, Issue 5, May 1979
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Volume 126 (1979)
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Volume 126, Issue 5
May 1979
Depletion-region width of p-n junction under high forward-bias conditions
- Author(s): L.C. Jain and G.N. Garud
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 361 –364
- DOI: 10.1049/piee.1979.0089
- Type: Article
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A new technique is used for the accurate analysis of linearly graded and Gaussian-graded p-n junctions, which permits calculation of the depletion-region width under high forward-bias conditions. Such an analysis is very useful for applications in which one wishes to analyse a complete junction-device structure (such as a bipolar transistor). The results obtained represent a considerable improvement in space-charge modelling over previous approaches to approximate linear analysis. The computer algorithm is discussed as a solution process for implementing the scheme.
Error probabilities for Viterbi decoders with correlated noise
- Author(s): J.K. Potts
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 365 –367
- DOI: 10.1049/piee.1979.0090
- Type: Article
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p.
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An upper bound can be calculated for the decoder error probability of convolutional coded data with Viterbi decoding by summing the numbers of error paths weighted by the path preference probabilities. This method can be readily applied for uncorrelated errors, but, for correlated noise, particularly with soft decision, the calculation of the path preference probabilities is more difficult. The method of importance sampling has been applied to this calculation using the noise-covariance matrix as input. Some results obtained by applying this technique are presented and compared with simulated decoding.
Computer-aided design of thyristor circuits: the sparse-network tableau approach
- Author(s): E.J. Prendergast and R.D. Jackson
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 369 –374
- DOI: 10.1049/piee.1979.0091
- Type: Article
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Developments in sparse-matrix handling techniques have resulted in the emergence of the network tableau as an important method for a computer solution of network equations. This paper considers the use of the tableau method for the computer-aided design of thyristor circuits and illustrates the method with two examples. The tableau method is described briefly, the problems of sparse-matrix handling, numerical integration and thyristor modelling are introduced.
Arc-back current in convertor systems: theory and experiment
- Author(s): M.A. Slonim
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 375 –380
- DOI: 10.1049/piee.1979.0092
- Type: Article
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The literature giving theoretical analysis and experimental data on arc-back currents in convertor systems is reviewed. An analytical method is recommended, and a solution of the arc-back-current problem in the full form is obtained. Experiments and numerical analyses were carried out and good coincidence of results was obtained.
Current-zero disconnection of induction motors
- Author(s): S. Sriharan
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 381 –384
- DOI: 10.1049/piee.1979.0093
- Type: Article
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The disconnection of an induction motor from its supply, by the interruption of the stator currents as they pass through their zero values, is analysed using permissible approximations. The disconnection by current chopping, of a single motor as well as a group of motors, is also analysed. For a single machine, the rotor currents given by the two analyses are very close even for a small machine, because the difference is determined by the open-circuit, rather than the short-circuit, decrements during the quarter cycle taken for current-zero interruption. Computed results for a small and a medium-sized motor, obtained by numerical integration, are presented to validate the approximate analysis of current-zero disconnection, and to confirm that the transients on reconnection of the machine to the supply are almost independent of the way in which the disconnection takes place. Thus, quite accurate predictions of transients following current-zero disconnection are obtained if current chopping is assumed; this simplifies the computations. It is found that the discrepancies are generally least when a chopping instant μ/6 rad after the current zero is chosen. The general conclusion is that the computationally convenient method based on current chopping is always applicable, whether or not current-zero interruption takes place.
Agile computer control of a turboalternator
- Author(s): D.J.N. Limebeer ; R.G. Harley ; H.L. Nattrass
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 385 –392
- DOI: 10.1049/piee.1979.0094
- Type: Article
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The paper describes the design and implementation of a new type on nonlinear digital controller. This controller and other comparable ones are evaluated by implementing them on a laboratory microturboalternator system coupled to a minicomputer. Offline theoretical predictions of the system response, based on a comprehensive mathematical model, are presented. The results show that the transient performance of this new controller compares favourably with that of existing digital controllers. A novel nonrecursive solution to the discrete Riccati equation is also demonstrated.
Computation of torque and current in doubly salient reluctance motors from nonlinear magnetisation data
- Author(s): J.M. Stephenson and J. Čorda
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 393 –396
- DOI: 10.1049/piee.1979.0095
- Type: Article
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The paper presents a new method for accurately calculating the torque and current of a variable-reluctance stepping motor from measured or computed flux-linkage/current/rotor position data. The new method is more accurate and uses less input data than previously known procedures, and is computationally efficient. It can be applied to both steady-state and transient problems.
Computation of impulse-voltage stresses in transformer windings
- Author(s): R. Kasturi and G.R.K. Murty
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 397 –400
- DOI: 10.1049/piee.1979.0096
- Type: Article
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p.
397
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Trapezoidal rule of integration is used for the computation of impulse-voltage stresses in transformer windings through a companion-network approach. The method is compared with two other methods, one based on eigenvalues and eigenvectors and the other based on series expansion of the state-transition matrix. The method is also verified by comparing it with experimental results.
Measurement of sequence impedances of a transformer
- Author(s): B.K. Sarkar and A.K. Mukhopadhyay
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 401 –402
- DOI: 10.1049/piee.1979.0097
- Type: Article
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In the paper some experimental methods of measuring sequence impedances of a 3-phase delta-star transformer have been developed. Easier methods of predetermining these impedances have also been discussed.
Nonlinear single-variable optimisation studies of a.c. turbogenerator performance
- Author(s): A.R. Daniels and H. Lu
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 403 –410
- DOI: 10.1049/piee.1979.0098
- Type: Article
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A synthesis method is described that is used to produce optimised excitation control of an a.c. turbogenerator when subjected to a large disturbance. The proposed controller incorporates only one extra feedback signal into the excitation system in addition to the normal terminal voltage feedback signal, and the relative merits of four such proposed signals are fully discussed. The method uses single-variable optimisation techniques, incorporating successive quadratic or cubic approximations of a nonlinear polynomial, and, by using dynamic sensitivity methods, gives important additional information on the relative suitability of each of the four proposed feedback signals. An experimental investigation performed on a laboratory micromachine system is also described, and confirms the trends in changes in system transient behaviour predicted by the theoretical studies.
Prediction of torsional oscillations in turbogenerator units connected to series compensated transmission systems
- Author(s): J.R. Smith ; H.M. Abd-Allah ; K.M. Jones
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 411 –420
- DOI: 10.1049/piee.1979.0099
- Type: Article
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p.
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Electromechanical interaction between long-compensated transmission systems and turbogenerator units may produce a distinguishable mode of torsional oscillatory behaviour that does not occur with conventional systems. This interaction is a result of subsynchronous resonance between the compensating series capacitance and the system reactances. A serious situation can arise when the transmission circuits have a low value of resistance due to conductor bundling, in conjunction with a series resonant frequency which, when viewed in terms of individual rotor angular speeds, coincides with a natural torsional mode of a generator shaft system. The paper reports on a study of subsynchronous oscillations and their effect on the shaft systems of conventional and multiple shaft turbogenerator units. Emphasis is placed on the investigation of a practical range of mechanical-parameter variation encountered throughout the load range of a steam-turbine unit. The simulation model used in the numerous studies undertaken is summarised, and representative results are collected together to show the various conditions that give rise to this category of instability.
Steady-state analysis of an induction motor fed from a current-source inverter using complex-state (Park's) vector
- Author(s): V. Subrahmanyam and D. Subbarayudu
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 421 –425
- DOI: 10.1049/piee.1979.0100
- Type: Article
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421
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It is shown in this paper that the complex state vector of the rotor flux of an induction motor fed from a current-source inverter has a locus which is almost circular at higher operating frequencies, even though the stator current vector has a hexagonal locus. As a consequence, the induced stator voltage is almost sinusoidal superimposed with spikes whenever the current in the stator winding commutates. A closed-form solution is given to describe the physical behaviour of the machine. There is a good correlation between the analytical and test results.
Electrical interference in pulsed-power technology
- Author(s): E. Thornton
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 426 –432
- DOI: 10.1049/piee.1979.0101
- Type: Article
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The sources of electrical interference in pulsed-power systems are considered, an attempt is made to quantify the levels encountered and techniques for interference reduction are discussed. It is demonstrated that electrical interference is a total-systems problem and it is suggested that it merits consideration in the early design stages.
Development of pumped storage in a power system
- Author(s): A.M. Cochran ; D.E. Isles ; I.T. Pope
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 433 –438
- DOI: 10.1049/piee.1979.0102
- Type: Article
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433
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The pumped-storage hydroelectric scheme is by far the most widely used and best-developed method of storing electrical energy. Because it is a net consumer of energy and its function is to make better use of other energy producing plant it is clear that there must be a practical limit to the proportion of pumped-storage plant which can be accommodated on the system. A 3-stage method has been adopted. The first stage is a feasibility assessment, which gives an indication of the quantity of pumped storage that could be accepted on the system. The other two stages involve a more detailed examination of the effect of pumped storage on long-term system security using Monte Carlo simulation and a study of total generating costs, including both capital and running costs. The methods are appropriate for assessing the characteristics of future pumped-storage developments on power systems with a significant proportion of existing hydroelectric and pumped-storage plant. They should also be applicable to systems containing very little hydraulic plant.
Load-controller design for a regulating coal-fired unit
- Author(s): J. Waddington
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 439 –445
- DOI: 10.1049/piee.1979.0103
- Type: Article
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The design of a load controller suitable for loading a regulating coal-fired unit is described. The target power and loading rate to reach the target are set by the unit operator. Such loading is achieved by setting the fuel demand and controlling the governor valves to maintain the final steam pressure to a set point value. Frequency regulation is facilitated both by modifying the fuel input and manipulating the pressure set point to release boiler stored energy. This ensures that the stored energy is preserved for short-term regulation and is not used for less urgent requirements. A generated power-trim loop is included to compensate for plant variations and nonlinearities and, additionally, the fuel input to the boiler is reduced if the steam pressure continues to rise once the governor valves are fully open. An analysis of the stability of the plant when coupled to the grid system shows an improvement relative to the stability when employing conventional master pressure control of steam pressure.
Discussion on “Resonance effects in stepping motors”, “Analytical method for estimating electromagnetic damping in a multistator stepping motor” and “Unifying approach to the static torque of stepping-motor structures”
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, page: 446 –446
- DOI: 10.1049/piee.1979.0104
- Type: Article
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Quasi-interpolar effect of armature banding in a d.c. machine
- Author(s): L.A. Agu ; S.A. Nasar ; J.J. Cathey
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 447 –448
- DOI: 10.1049/piee.1979.0105
- Type: Article
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Erratum: Subharmonic resonance in stepping motors
- Author(s): A.P. Russell and I.E.D. Pickup
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, page: 448 –448
- DOI: 10.1049/piee.1979.0106
- Type: Article
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Synthesis of optimal block controllers for multivariable control systems and its inverse optimal-control problem
- Author(s): Y.J. Wei and L.S. Shieh
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 449 –456
- DOI: 10.1049/piee.1979.0107
- Type: Article
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A new method is presented to synthesise optimal block controllers for a class of multivariable control systems represented by the block companion form. The reverse process of obtaining the optimal block controller is used to determine the block-weighting matrices of the quadratic performance index from prescribed control specifications.
2nd-order Volterra kernel measurement using pseudorandom ternary signals and discrete Fourier transforms
- Author(s): H.A. Barker and R.W. Davy
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 457 –460
- DOI: 10.1049/piee.1979.0108
- Type: Article
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A method is developed for the measurement of the values of a 2nd-order kernel in a Volterra-series representation of a nonlinear system, using the discrete Fourier transform of the system output sequence when the system input is an antisymmetric pseudorandom ternary signal. It is shown that the inverse transform of a product of the output transform and the transform of the square of the input sequence yields a crosscorrelation function from which estimates of the 2nd-order kernel values may be obtained by an established procedure. Properties of the discrete Fourier transform of the square of an antisymmetric pseudorandom ternary sequence are developed and used in a comprehensive procedure for estimating the linear frequency response, 1st-order kernel and 2nd-order kernel of a system with minimal computation.
Simple method for the design of single-input optimum regulators and servomechanisms
- Author(s): J.K. Pal and P. Purkayastha
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, page: 461 –461
- DOI: 10.1049/piee.1979.0109
- Type: Article
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Reply: Simple method for the design of single-input optimum regulators and servomechanisms
- Author(s): M.J. Grimble
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, page: 461 –461
- DOI: 10.1049/piee.1979.0110
- Type: Article
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Influence of humidity on the sparkover of rod-rod gaps of several geometrical forms subjected to positive impulse voltages of varying waveshapes
- Author(s): T.E. Allibone ; D. Dring ; N.L. Allen
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 462 –466
- DOI: 10.1049/piee.1979.0111
- Type: Article
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The humidity correction factor suggested in BS 923:1972 for sparkover under lightning and switching impulse voltages relates to rod-rod gaps; there is no suggestion that the factor might vary with the actual geometrical shape of the termination of the rods, with gap spacing or with waveshape of the applied impulse. Large variations of the correction factor have been found as each of these parameters is changed, and the observed values have been discussed in relation to the inception times of corona formation and times to sparkover of the gaps.
Dynamic demagnetisation of relatively large ferromagnetic bodies
- Author(s): B.D. Popović and A.R. Djordjević
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 5, p. 467 –468
- DOI: 10.1049/piee.1979.0112
- Type: Article
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